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MG MGF Technical - Final answer to running problems

Calling all experts.
At risk of boring the world;
I have searched through hundreds of chat's on BBS about engines shuddering at low revs, and/or cutting out in the process - normally you rev to 2000 revs, then suddenly they all drop - this normally all goes on when the car is cold.., and you're in traffic.

The suggesions fix this are to replace the: -
Coil, HT leads, engine management, sparks, and oil. - (and full service)
[Done all this] :-(

People have written in over the years saying they are trying to fix it with a new: -
Engine Bay Wiring Loom,
wiring to rear-crank sensor play,
MAP signal,
Coolant Temp. sensor,
throttle potential meter,
inlet manifld pressure sensor,
solenoids, and
inlet manifold vacumn pipe.

For someone like me (and there must be many others), I've done my first five visits back to Rover, spent my first grand trying to locate the problem, stalled all over the shot and done the odd impression of Skippy in wet concrete.

So, - at risk of boring the world - has anyone actually had this problem and fixed it?
We must all have the same thing.. ?
Surely it can't be all of the above?

Pls save my pocket so I can afford nice bits for my car ;-)

N Hillier

Well done on the research and comprehensive summary!
I'm afraid i cant help much, just to clarify that HT lead upgrade , rather than replacement with same type, helps wet starting in VVC's particularly.

My '97 VVC, has the revs drop to 0 then kick back to normal idle speed when engine is warm, weather damp and in traffic. Root cause unknown but will try HT lead upgrade at next service/opportunity.

If its electrical, would it be traceable via Testbook?

Anyone else have any Ideas?

Something that has never been mentioned here, but has come up in the Elise board is injectors, if you remove the plugs are they all the same colour, or is one 'cleaner' than the others? if an injector is not opening properly then it will under fuel that cylinder leading to knocking, the lamda sensor will detect the engine is out of balance and it will add fuel to all cylinders, this will lead to 1 lean and 3 rich cylinders.

It's worth a look!
Will Munns

Tom Randell I think solved the problem on his car - although quite what the problem was, I am not sure...
Rob Bell

I had a similar problem on my F. Tightening up the outlet pipe on the fuel pump (this was leaking petrol into the engine bay) and fixing a loose wire in the connector to the ECU cured the problem. I suspect that it was the latter of these that was the actual cause of the problem, but I can't be certain.


Know how you feel - been through all of the above myself over the past 2 years - still haven't located the problem. Testbook told me it's the MAP sensor, which picks up the symptom not the cause. Reluctantly I changed it but it didn't cure the problem.
I fitted a 52mm TB and a Trophy 160 induction kit with a pipercross flat filter still no joy except it run with more power.
I spoke to the local MGR service centre a couple of weeks ago - they had an MGf in recently with the same problem and after several days couldn't locate the fault.
I'm tempted to fit a pressure gauge to the fuel pump and see if I can pick up any fluctuations in pressure but that's a long shot.
The other thought was the Cat maybe partially blocked as most of the failures happen coming of low revs. Kill the engine and restart taking it to about 2,500 revs sees to clear it for a few weeks.
Meanwhile the Rover is running well.


As Rob mentioned I had a massive electrical problem last year which went on for over 4 months.

The symptons where the car would not start, reves would drop and stall, miss firing. Car is a 1.8i march 97 model.

I had new (things which I know about) HT leads, spark plugs distributor cap, rotor arm, crank sensor engine bay wiring loom, main wiring loom, engine management catalic converter.

As can be seen I had quite a lot change and the above are things which I paid for but I suspect other things where changed which are not on the list.

The car spent most of the the last 2 months in the garage and to this day do not know what the problem was nor the actual cause but it cost just under 2500 for the fix and that did include help from MGR/dealer.

The dealer was stumped and there last resort was to have a donor car and change everything to do with the engine over which did not fix it thus they change the only thing left which was the main wiring loom.

Hopefully this will never happen again.

There was someone else who had a similar problem who had it fixed bu and auto eletrician I think from memory he was John from nottingham.

Tom Randell @ work

I remember Paul Weatherhill had problems with idling when he added a TB and Viper to his car, and ended up getting a new fuel pump or regulator. Didn't think he had any of the other symptoms though.

Thanks a lot for all the input guys :-)

Very pleased to have found this site..

John (Philpott) did indeed contact me, saying that he eventually solved the problem by getting an independant electrical specialist to take a look at his motor.
"The core fault lay with the MAP (manifold absolute pressure)
sensor which - on the 1.8 MPI - is integrated within the MEMS. The guy I
took it to offered to customize the MEMS by giving it an external (and
better performing) General Motors MAP sensor and this cured the problem."

I was not sure if this applies to the VVC also.., but sounds like this cure, the new wiring loom some people had done AND some of the other fixes may all be roughly the same thing.

John also stated that the dealers were unable to dignose it as it appeared just within the allowable range in the MG testbook!

Personally, if it doesn't get worse, then I can almost live with the problem.., the trouble starts when the better half takes it out for a trundle!

If I get soildering, and fix this, I will let you all know.

Thanks again..

N Hillier

ohh sh*t, it looks like I have a long way ahead to have my problem solved.

I posted it a few times on this BBS... and the last thing I changed was the potentiometer of the TB.

Yesterday the problem happened again, after some engine braking the car starts to judder again and slightly pushing the accelerator makes the revs jumping between 600 and 1200rpm.

Turning the engine off and back on could cure the problem for a while... if it's not cured, a reset of the stepper motor will do the trick.

After changing:
- plugs
- HT leads
- rotor arm
- distributor cap
- lambda sensor (and exhaust manifold)
next thing will be
- stepper motor
- fuel pressure things (second, as we have the impression that the car is running rich during the problem).

BTW, gave up on MG-Rover dealer

Eric, have you checked the plugs for signes of lean/rich mixture?
Will Munns

>>> Eric, have you checked the plugs for signes of lean/rich mixture? <<<

No, .... but if the problem happens:
- the accelerator slightly pushed so that the revs are jumping, gives a fuel smell at the rear of the car.
- during driving (or trying to, juddering car), from time to time you could hear a misfire in the exhaust.

that's why we're thinking it is running rich, or the ingnition is way out.

As I said earlier, if there is a problem with an injector then the engine will try to balance the engine, this will turn out to be 3 cylinders running rich and one running lean, this would give you your problem. The diagnosis is free, just pull the plugs and compare.
Will Munns

Interesting Will.... would this show up when the car is connected to Test Book during the problem ?

Nope, the MEMS looks at the lamda sensor to tell if the _engine_ is in balance fuel/air, it has no way of knowing if one cylinder is rich/lean so it adjusts all of them.
Will Munns


Is this the same problems as on the Treffen? As I seem to remember MS looking at the plugs for these signs.

Ted Newman

<<I remember Paul Weatherhill had problems with idling when he added a TB and Viper to his car, and ended up getting a new fuel pump or regulator. Didn't think he had any of the other symptoms though.>>

Actually, ended up being a loose throttle postion sensor.
paul weatherill


Unfortunatly it is the same problem. As the problem doesn't show up every journey, it is changing part A... waiting... finding out that the problem is still their and changing part B... and so on.

Mike did change the plugs, but don't know if the engine was shut down, the plugs removed when the problem occured. Could be that the problem was there, engine powered off, reset stepper motor, start engine again... power down engine again and have the plugs removed. I need to check the bill for that ;o)

C ya


The CAT is empty!!! The engiene need some resistance to work propperly, so if the cat is empty then the engiene jugges...



The problem is there with and without a cat... and powering off the engine *could* cure the problem... but it couldn't fill the cat.


Never had a problem on Scarlet Magnus, been running using a mild steel cat-bypass since 1998 (long enough for it to go rusty enough to need a new one!)


Interesting point about the fuel injectors Will, i can see how this might make the car run rich and lean at the same time, but would it cause the 'pulsing' that Eric describes? To be honest, this has been worrying me ever since i saw it on the Treffen, it's almost like a feedback loop in the MEMS, the car tries to stall, but the MEMS won't let it - all very odd.

Scarlet Fever


Do you gain some extra power with the cat-bypass?


I recently went down the cat bypass route and I think you gain a little but I couldnt put up with the noise ! I could pretty much guarantee to set off most car alarms in the vicinity.. I kept it on for one day only..


>. if it's not cured, a reset of the stepper motor will do the trick.

Seams that this reset cures some other problems as well.

Yes, I now have one as well, but going in the opposit direction. No cut out at low revs.
No, but higher revs in idle mode (1.500) and very slow decreasing engine revs when I release the accelerator. *intermittant*

It looks like the same as Stu D. reported the other day.
Cured with stepper motor reset as well.

I'll try to explain.
Went home for the 300km ride on wednesday. Quit nice warm ambient conditions with 28 C.
At first it happend that the EPAS light came off and didn't reset with *ignition out and on*. Anywy, I went on ond after about 15 km on the motorway the EPAS light went dark. OK so far, going on with 80mph hood open.

150km later a traffic jam. Stop and Go traffic and I felt anything strange with the engine revs (engine brake) but didn't notice or look after any more.

Another 50km (230km/h now) to the next traffic jam. Released the accelerator to slowly reach the car in front with help of the engine brake (spelling?).

Looked at the speedo.. hmmmmm, speed decreased slower then usual, kicked the clutch, geared down, geared up and back down to fourth .... looked at the tachometer... Doooh, Engine revs nearly rested at 3000 revs and decreased very, very slow down until the reached 1500 after a couple of seconds. Stopped the car due to the traffic jam. The engine with idle 1500 revs. Stopped the engine, started again ... revs went just up to 1500. Kicked the accelerator.. same as before with slow rev decrease. Tried this speed increase / decrease game some more times with the same faulty result.

What's that ? I joined the next car park and did the *stepper motor* reset, as known.

*g* everything back to normal fast rev decrease ... but the EPAS light was off again for the first 100 meters... ;)

I looked up the archives for similar reports about high idle and collected about 10 threads since 1999. From Dirkie over Jason to Stu, always nearly the same and now with my car. I'm very sure it is not a sticking throttle or sticky throttle cable.

Throttle position sensor and affiliated wiring sounds a reasonable theory at my car. I DIY changed the wiring and played with it when I swapped to the Vauxhall TB in last year.

Will keep and eye on it and the next it happens I'll open the engine bay and rattle the cables and connectors before I reset the stepper.

Is this worth having a survey with a new thread ???

Who had which problem with high or low idle mode and what was the approved final solution ?
( sticky throttle, sticky throttle cable as the well known mechanical troubles and *unknown ongoing electrical problems* broken TPS wiring, broken TPS and what else.

Anyone good for setting up a reasonable questionaire ?

1.8i, MY1999, 45.000 mls
PS. EPAS light stays dark currently after I rattled at all fuses in the bonnet. Whatever this means.
Dieter K.

>>> (230km/h now) to the next traffic jam <<<
Stop doing this... it's rather unsafe to join a traffic jam at a speed of 230 km/h ;o)

I was noticed the phenomenon of sticky revs (also noticable during the period of changing gears) just after swapping the TB... than it was caused by a) not resetting the stepper motor b) the cable that was pulling to hard at the butterfly mechanisme.
Off course, this couldn't help you I guess :-(


> it's rather unsafe to join a traffic jam at a speed of 230 km/h ;o)

:) no worries. My speach troubles. I meaned I had high speed for a couple of miles until I had to slow down due to the traffic jam. It didn't just appear. I liked to say the engine was hot with about 125C Oil temp in this case.
It was quite lower with 100 C when I did the first distance and started realising there was anything strange with *engine braking*.

>Off course, this couldn't help you I guess :-(
Yep, doesn't help cause in my above case the *a)* helped but I'm after the *reason*.

Why not collecting the ideas as we usually did years ago with similar complex *problems* :)

...the Erik of the day.....
>I was noticed the phenomenon of sticky revs (also noticable during the period of changing gears) just after swapping the TB... than it was caused by
a) not resetting the stepper motor
b) the cable that was pulling to hard at the butterfly mechanisme.

Any more ?

Dieter K.

See archives, but bad connections/faulty TPS caused my lack of engine braking.
Nothing showed up under test book. Was a broken wire within the TPS connector.

Paul Nothard


verified the problem this morning at the ride to the workplace. Another 300km.
Problem started at 100km. Did the first Reset on a car park.
Then nearly each 50km the same (4 times !!), but I know I learned to reset the stepper without stopping the car.
Push clutch, Ignition off, *reset sequence*, ignition on and release clutch like at jump start.
Works well, but I don't like it.

I did some AVI files from the moving tachometer and will host tonight. :))))

It's by 100 percent not the TB bowden cable or the TB flap itself.
I rattled at the TPS connector while high ideling (at the first stop). No change of revs.
Will update more soon .

Dieter K.

Above story now online with some MPG files (poor Quality as well the website, apology in advance)
To be improved .... watch that space.

BTW, I think I'm 100 percent sure this high rev curiosity was at my MGF just from the beginning of the ownership.
I never realised in this way, cause I almost go long distances on Motorways and never got the mad idea to puch the clutch and take the foot from the accelerator *just 4fun* due to verify the idle revs... ;)

In short distances it didn't happen or I though on *pilot error* or I moved my mind on the *sticky plastic throttle syndrome* .
Changed the flap to the Vauxhall at last but the so called problem is still there.
I'm as well sure it isn't the connector to the TBS, casue I had it fully dismantled to change the outer spade connectors.
Wiring to the ECU is another story.
To be checked the next within a few weeks.

I'll see for a voltage meter and connect it parallel to the TBS outlet. I wonder what will happen then with it.

PS how should MPG files be correct included to HTML files ?? Any good IT suggestion ??
Dieter K.

I had an avi from a while ago, so I followed Dieter and putted it on a website:

This afternoon I placed an order for a new stepper motor... I'll keep you guys updated off course.

Dieter, next time the road is safe, try to invoke the problem with some engine braking... curious if it's also a strong trigger as it is in our situation.

the same thread is running at the german BBS.

some useful input/ideas:

- has anyone out there with a new EDC3 MY 2001 MGF a problem with high revs like we discuss ?

I can't remember. Anyone ?
If not then I'd be very curious what's it about to do with the TPS or wiring in principals !!!

The second message I found interesting is a bit difficult to expalin late in the night.

Hannes, an MGF Oldie from DE said he had spotted the video (mine) and remembered having had the same.
Now it's fixed after no solution with TB cleaning. His mechanic had opened the throttle flap for some tenth of mm. He just turned the *idle adjustment screw* to *open* for half of a turn and gave the engine some air when the flap should be *closed*. This cured the problem at his car. Stepper Reset requeired of course.

I think I'll try this with the Vauxhall TB when I go back the 300km on friday. Put a washer under the joint or easy things like that including new reset.

Dieter K.

Hi all,
interesting thread... Possibly worth a new "heading" so it can be easily found in the archive later on !

My 5p worth of input: In order to get ANY increase in revs there has to be a certain amount of air entering into the cylinders. If we assume that the throttle IS correctly closed when the throttle cable is free this air must enter from somewhere else... The next candidate for letting in air is the opening that is controlled by the stepper motor. Also there is a possibillity of other leaks,but apart from the vacuum hose to the brake-servo they are going into the throttle body and hence controlled by the throttle opening... So IMO either the stepper motor,inlet vacuum sensor (hose on Mpi ) OR back-pressure valve in the brake-servo could be playing up. Remember that resetting the stepper motor only adjusts for the amount of ait passing to get correct idle - it will then also "correct" for any intermittent leaks! As far as I know the stepper motor is without stops in its turning , this is the reason why the MEMS has to count and store number of steps for a certain amount of opening . In the old days there was this vacuum-meter that was attached to the inlet after the carburator/throttle. Properly used the readings could tell a lot about condition of valves, timing,leaks etc.

BR, Carl.
Carl Blom

Hi Carl,
big thank you for the ideas on the matter.
LOL... I just joined the BBS to send you a copy of this thread to get your judgement. OK, now I have and will see what can be checked.
BTW the German guy wrote today that he had temporary in already another ECU at the dealer. Notb approved currently. May be he missed the right part descriprion in his message.

Erik, are you out there ?
I think your cars silly stepper motor *saw tooth* behavior could be related as well to what Carl said.

Dieter K.

Erik, are you out there ?
I think your cars silly stepper motor *saw tooth* behavior could be related as well to what Carl said.

I am here.... could it be related to the inlet vacuum sensor, hose and/or brake servo valve thing.... Another test I will do (as I do read the postings of Carl) is connect the connector of the TPS in the other way, just to make sure it is even worse when this one is wrong.

The archive of the Elise BBS do mention a lot of sticky revs problems and cleaning the IACV (idle air something or the thing controlled by the stepper)

>cleaning the IACV
Not sure, I think it's the stepper motor, is it ?

Anyway though about the brake servo valve and vacuum pipe.

I remember an advise from MGR DE regarding the front bonnet box (DE only) and the other official product change of the black coloured bonnet cover. *Notive due to keeping enough space for the hose where it enters the servo*.

Didn't it speak about leaky hose to the brake servo ?
Anyway, I think a leak at the servo itself would cause lack of brake power on first had. Would a tiny leak affect the vakuum level in the manifold as well ?

Anyway, one term I gon't get is why in heaven appears the high idle like a *cruise control* when I have done 50km++ ?

I do nothing but drive constantly app. 90mls/h
- take the right foot from the accelerator,
- push the clutch and revs go down only slow and rest at 1400. ??

Dieter K.

Hi Dieter

Yep this is spot on!

>>I do nothing but drive constantly app. 90mls/h

- take the right foot from the accelerator,
- push the clutch and revs go down only slow and rest at 1400. ?? <<

I am still occassionly getting the same problem and when my does it the revs actually increase by 300-400 before dropping slowly!! to around 1400 then slower still down to 1000..

Stopping and reseting the tps seems to cure it... but not always?

But like i say this is very intermitent, it will be ok for a couple of days then play up again!

Havent had time to look into it properly yet but will do at the weekend..


I followed the link on the Immobilizer thread, having a look around it seems that the Fiesta has a still idle and a moving idle, to test it you have to take the car out of gear, push car until you exceed 11mph, and if the idle goes crazy then you have a problem with the speed idle.
Is it possible that MGR have this in MEMS?
Why would you want it?
Will Munns

@ Stu,
>Stopping and reseting the tps seems to cure it... but not always?
Jep, sounds like the same with mine. Not always.
Anyway, I'll do some tests again when driving home on Friday and another on white sun weekend.
Copied this thread to a file already and get back with it later in next week.
Header: *high rev idling / saw tooth idling*

@Will, yes I thought as well on similar options.
How in heaven should I find someone who pushes the car to 11mph for this test and over a distance of 50km ... until it happens ??? ;) LOL ....

Dieter K.

Had a little chat with one of the technicians yesterday and he doesn't believe in changing the stepper motor.

He's more thinking about a sticky inlet valve not closing completly, messing up the vacuum in the inlet manifold. MO, it ain't funny anymore, 'cause these things are getting a bit expensive.

Anyway, will change the stepper motor and its housing shortly and report after the weekend.


no change, still the same :( but had some great wine :)


stage 2. testing......

I just got back from a great MGCC meeting, (annual big on at Montabaur castle).

On the way home the problem occured as usual after the first app 80km.
Stopped at a 'Autobahn Restaurant' and did the reset.
Started... problem gone, normal idle.

Then I put a piece of folded paper (app 1 to 2mm mm) together with adhesive tape on the throttle lever joint to lift it and produce a gap with the butterly inside the throttle body. (GM body in my case)
Started the engine and it had idle at about 2.500 revs.
OK so far, I reset again and went home for the remaining 60 km.
What should I say... no high idle as I suspected in the next 20km. No it was fine.

Spotted new effect:
the engine revs remain for app 1/3rd of a second at the high revs and go down the quick as usual.

I'll go for the 300km ride tomorrow and report what happened.

At Erik:
Mate I think this is worth a test 4you. No idea whether it helps or gives any useful result, but it seams different, whyever ???

I put a pic on site, so you can see where to put anything with adhesive tape to the joint. You can scrw down the joint bolt as well, but don't ask me how to get it back to the 'standard' location. There the nut you need to make loose before you screw the bolt downwards.
Stepper Motor reset must be done of course to get normal idle. far down on te bottom.

btw, can anyone explain what happens if the butterly provides a tiny gap and gives constant small airflow to the manifold ??

The TPS initial signal (ZERO) is <of course higher then normal and the stepper needs less opening.

Looked up all MEMES ECU related input output signals already to get fursther with more tests.
One candidate of suspect is the crank sensor. Any ideas on this ?

Dieter K.


I think our cars are telepathetic... thats is exactly the same thing i occasionly get, either the revs seem to hold for a brief period or in the worst case the revs will actually go up a few hundred b4 dropping..

But its wierd today i have driven about 200k and its been fine..

Havent really had time to investigate further but i'll be watchin your posts..

hope all is well with you and yours.....



... well so far, but *drives me nuts* ;)
I still think it's from the beginning since I have the car.
Dieter K.

Mines only started doing it a few days after the return from Cote d'azur...

Might try changing sensors one by one but bit of an expensive option!



are you coming over for Silverstone?


Could the purge valve in the EVAP Canister be incorrectly operating and causing this strange idle? The MEMS may be faulty and cause the purge valve to operate at idle revs instead of above 1800 rpm. The increased flow of air to the mainifold would then make the revs rise. It would be easy to check by connecting a wire to the purge valve connector and run it through to the cockpit to a small light so you could see when it comes on.

Bruce Caldwell

Hi guys,

Replaced the stepper motor and its housing on mine and cleaned the pipes in the neigbourhood. All clean, except the connection from the stepper motor to the "inlet manifold".

Also checked if the connector of the TPS was correctly fitted and it was.

Anyway, drove +300kms on Saturday, and the problem didn't occure once. I'll keep my fingers crossed.

Wish you are right.

Please take the hint on opening the butterfly as a temporary try only. I've done a short ride this morning with cold engine and the *open* butterfly as written above...
No that can't be a good final solution. I think the engine idle runs... ahmmmm ,crap.
Cold start is OK, idle at 1200 going down to 9000 if warmed up. But the short *break before slowing down* remains if I push the clutch.

In half an hour I go for the long ride to work and I'll have some different tests.

@ Will, I take your point.
@ Stu, unfortunately I can't make it. We move ...

Dieter K.

@ all, special 2 Will and Carl.

YES !!!!
I think I found something.
Vacuum relation & Purge Valve seams to be the trouble in my cars case. Thank You Carl and Will for the hints !!

In short, did the first 120km with increased throttle butterfly *gap* without the high rev problem.
Then I though about Will's idea with the purge valve.
It is a solenoid driven valve (one way, open/close).

Should be powerded with ignition on and the vacuum hose on the right of the throttle body gets connected to the big black plastic can...

I stopped and measured power at the brown-pink wire. There was.

I pulled the connector and pushed it back ... no *switch noise*, no idle change.
Then I removed the valve block (bend plastic seam below the hoses and carefull lift off the valve.
(only pix of the location, not from below)

On the bottom of the valve block is a short inlet pipe joint (app. 8mm dia. and 10mm high). It just sits against an O-Ring in the purge valve can.
So I held in my hand the powered valve with inlet joint.
Hmm... I should hear a suction noise, shouldn't I ??
But there wasn't. Pulled the connector, no noise, no click, nothing. put the thumb on the pipe joint, nothing.
Measured power again at the spade connectors. Power is there.

Conclusion is easy, Ehyyy ??
The crap thing is dead !!!!!!!!!1

But why should a dead valve result in high idle ?
Here my theory....please comment and correct it.

I believe the valve works, but only intermittent after a couple of miles. At first from cold engine after app 70 miles when the throttle butterfly seals frequently. In that case it gets vacuum pulses ... sometimes and frees in any way.
The valve was closed and let no *wrong air* to the manifold when I started....but now suddenly it did, which results in high idle and slow going down stepper motor.

Then I reset the stepper to the new *standard air flow* conditions and went on. Here my theory fails, cause I have only few ideas why idle is high again after another 20 miles. Anyway, this could relate to adaption of MEMS ?

However, I think my opening the butterfly by some mm provided the *missing flow from the purge valve* and the vacuum pulses where missed as well, cause the butterfly never sealed as before.

Does this sound reasonable ??????

Anyway. Seeing this theory, I decreased the gap (used only 0.5mm paper between throttle lever and joint).
This resulted in no high idle for the other 200km ride to works.
It's fine currently, even the purge valve doesn't work.

A plea to Stu,
Mate could you try removing the connector or the hose to the inlet manifold from the purge valve and report what happens at yours ?
If it's blocked as at mine then the idle should go up.

Same with Erik. Please test whether the purge valve works if you switch ignition on.

PS. any other thoughts on the damn valve appreciated. I'll replace it and cut the broken with the *hack saw* on Friday when I get home. (have a spare from the wreck)

Dieter K.

Hi all,
the coal-cannister can be a bit hard to understand how it works and have puzzled me too !

1. The brown/pink wire (as also used in the "delayed" circuit) has power (+12Volt) from the MEMS whenever the engine is running AND some minutes after switch off.

2. For safety and ease of switching all gadgets in the car are switched by adding a ground-path via the MEMS. This means that most things as coils,valves (as this one in the canister etc.)allready have +12Volt on one side and only needs a return to ground via a series transistor in the MEMS to be actuated.

3. For emptying the coal canister this ground connection via the MEMS occurs when the engine is warm and accelerating under load. This can sometimes be heard as a hissing sound for a few seconds when the valve opens and exessive fuel vapor enters as an enrichment during acceleration.

4. So the main question is : Is the valve working as intended or malfunctioning. The advise from Bruce to place a small lightbulb across the valve solenoid is a good one. This will at least tell the electrical function. If the mechanics in the valve are OK is another story..... Any constant or intermittent leakage here will of course change the amount of air passing into the engine = change in idle and revs.

BR, Carl.
Carl Blom

Ooops, Will is Bruce, I'm sorry.

Looked up more for the purge valve stuff from manuals yesterday.

Official...but I've no idea whether this relates to newer only or as well to older cars (post MEMS3)
When the engine is above 75C, the purge valve solenoid will become operational (modulated ON and OFF) whenever the engine speed is above approximately 1800 rev/min.

... and...
The amount of fuel vapour which enters the cylinders can affect the overall AFR, therefore the ECM must only open the cannister purge valve when it is able to compensate by reducing fuel injector duration. The cannister purge valve will only operate under the following conditions:
Engine at normal operating temperature
Adaptive fuelling enabled
Closed loop fuelling enabled.
Last 2 points most confusing even with the german language version. No idea what they mean with
> Adaptive fuelling enabled
> Closed loop fuelling enabled.

Though I'll check the purge valve in any on both wires.
brown-pink (+) and the yellow-orange which does the on/off operation to ground over the ECU.

I wonder about the timing and delay due to the *above 1.800 revs at +75C* signal.
As said above. At my car it didn't switch.
This must not mean the valve is broken. Can be anything else, but what ?
I don't think it's the fly wheel sensor.
A sticky purge valve sounds the easier way ;)

Dieter K.

> Adaptive fuelling enabled

I think this means the MEMS is on the map it creates, not a 'cold start map'

> Closed loop fuelling enabled.

This means the MEMS beleives that we are neither accelerating or decelerating, and as such it can use the Lamda sensor to detect lean/rich changes in mixture.
Will Munns

Thank you.
I wondered, cause I'm not sure whether I could reproduce the purge valve *on/off* switching when the car is not rolling but sitting on a car park (warmed up of course).
75 Temperature and revs above 1.800 written earlier surely mean the same.

I think I have to follow Bruce advise with the light connected parallel to the purge valve for final approval. I think any time delay may be in as well.

PS. the hack saw can wait ;)
Dieter K.

Small update: so far so good, new stepper motor and housing and cleaning is doing its job. More kilometres will be covered during the weekend. I'll keep my fingers crossed and the multimeter in the boot.
If it happens again, I'll do the trick with the slightly opened TB, check some sensors and have a look at the purge valve.

have a nice weekend

>have a look at the purge valve.

Yep, I'm just starting for the home ride.
Multimeter in the boot.

Erik, don't forget measuring between both contacts of the purge valve. Not only the *life at power on* brown-pink.
Push in small tips or thin blanc wires as *adapter* careful to the spade connectors from rear and take care on the rubber sills inside.

CU in 3 hours :)
Dieter K.

Yoohou! back online. :)

Last report to this thread now from me.
I think I can put down my cars high idle problem to an intermittent sticky purge valve.
- Started with slight increased butterfly gap.
- 10km later stopped on a car park (idle 850 revs, engine was warmed up.
- opened the boot, restarted engine and had a near look to the purge valve block. This block was released from the cannister already (see above)
- valve in the left hand, pulled the throttle cable and increased revs above 1800.
*** hissing noise in my left from the valve block ***
No constant noise !! It is a pulsed in frequency of about 3Hz (can be 5Hz)
So it sounds *pfft,pfft,pfft* like a quick steam train :)))
- put one finger on the open f*rting connection and clearly felt the vacuum pressure from the manifold.
- decrease revs below 1800 stops it, increase starts it again. The frequency is not engine rev related, but constant.

Used the Digtal multi-instrument in 20Volt range to read out voltages.
- idle 850, voltage between brown-pink and the other (yello-???) was app 6 Volt.
- 2000 revs, voltage increased to app 9 Volt
(not 12 Volt cause IMO the integrating function of pulses)

I put all back in place and removed the paper from the butterfly joint to get back on the initial *failure* circumstances. Started the engine. It wnt at first to 850 and then *died* ... cause it got to less air from the IACV. I reset and then it was fine.

Went on the remaining 290 km and pushed the clutch several times after each 50km. Nothing to worry. The failure didn't appear today.

Anyway, a revised theory now leads me to the conclusion that the damn valve gets sometimes sticky at my car. May be it's ambient temperature related or whatever may cause it. I didn't see the vacuum pulse when I had the failure in last week.

If anyone out there gets the same, you need not dismantle the valve to get the feeling it pulses, or not.
No, just put one finger on the valve and increase revs. A slight *knocking* with 3 to 5 Hz frequency can clearly be felt if the valve works.

PS. I open another thread to this very specific failure: Idle high, intermittant sticky purge valve
Dieter K.

This thread was discussed between 28/05/2003 and 13/06/2003

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