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MG MGF Technical - Engine doesnt rev down

Hi,

When the engine's cold, the engine revs around more than 1000revs until it warms up Then it revs down around 700/800revs, right?

Yesterday I took the car to go to work and the engine did not rev down. It remained around 1000revs even after 1/2hour driving in the traffic. Same thing this morning.

Any idea where it can come from?

Thanks
Jérôme

Hi Jerome,

Sounds like a glitch with the coolant temperature sensor. or perhaps the MEMS itself. I've not had this problem on the MG but i have on one of my Vauxhall's. Fortunately it was under warranty and Vauxhall reprogrammed the ECU to remedy it.

Nick
Nick

Sounds like a the MEMS not talking with the thermostat. Have they fallen out? If its under warrenty just take it back and get it checked.
JFK

Throttle sticks – Engine keeps revs/speed.


When driving, if I take ease of or completely release the gas peddle, the engine revs do NOT fall back to idle. Its like driving with “automatic cruise control”. The problem also happens if the car is in neutral and the revs are built are slowly, then again the revs do not return to idle when the gas is removed.

The revs are reduced sometimes if you wait, or if you “blip” the gas peddle.

To make matters worse, the problem has now disappeared after 36 hours. I think a similar problem happened 2 months ago… but I thought it was the just automatic choke on a cold day settling down.

The car is 6month old at 6.5miles.

Any recommendations?




Jérôme,
Your issues is supiciously similar to how my car was 2 months ago. I my case the fault has become more serious.
Francis

The other area to look at is the the Throttle Body, slight distortion can cause this and MG/Rover have put out a bulletin on this problem.

Do you have a K&N (or other make) direct fitting filter with a Jubilee type clip? or have you had the original spring clip replaced by a worm driven clip?

Over tightening can cause such distortion and in consequence restrict the free movement of the throttle.

Ted
Ted Newman

Francis,

My 98S 1.8i does this too, engine revs sometimes hang at about 1-2k Revs, like you say - 'automatic cruise control'. A Throttle 'blip' sorts it out... Anyone know the cause? It doesn't happen much, seems random, though usually happens when I slow down to a stop in 3rd / 4th...

cheers,
Rich
rich

Ted,

Thanks for the tip. Do you mean the connection between the K&N cone filter and the engine? Rarely, but once in a blue moon, my engine will get stuck in high revs even though the gas pedal is released. A little tap on the pedal usually clears it though. I'll investigate the clips holding the K&N this weekend...

Always thougth it was one of the many Rover gremlins that come standard in MGF's...

Mike
Mike

Yep.

The round section on the engine that the black rubber pipe connects to is the throttle body and it can distort if too much pressure is applied and this will prevent the free movement of the butterfly flap.

Suggest you undo the worm clip completely then as per K&Ns instruction tighten so it just grips then give it (I think it says) just another half turn.

Ted
Ted Newman

MGF 1.8i nov1997 60000km, no K&N (not yet)

>>When driving, if I take ease of or completely release the gas peddle, the engine revs do NOT fall back >>to idle. Its like driving with “automatic cruise control”.

My problem only appears when the car is stopped in neutral. The engine idles around 1000revs
I don't think it comes from the gas pedal because it doesn't change anything if I blip it.
I'm afraid Nick and JFK must be right.

I think fuel consumption will increase in a short term but what can be the consequences of this problem in a long term?
Jérôme

always same things coming back, my suggestions, talking from experience:

1. grease a bit the butterfly flap
2. testbook - retune stepper motor
3. check solenoid(s)
4. check mems & sensors
5. check throttle cable

I got already 4st four as remedy for my idle revs problems, no.5 was done without having even the problem!
Dirk Vael

I have a standard 1.8I not modifications.

The fault happens at revs over 1K and up to 4K. Fault is first spotted when there is “delay” between letting go of the gas peddle and engine revs dying.

Jérôme, sound’s like your problem is either the "first warning signs" of what happenned to me or it's a differnt problem.

Many thanks for advice… I'll pass onto dealer. Car goes in on the 10th April. I'll report back any news.

Francis
V272 ROH
Francis

Yes, thanks guys.

>I'll pass onto dealer
So will I

Jérôme
at work, looking at the blue sky towards the window ;-(
Jérôme


Had similar problem with revs not dropping as they should.
I managed to trace this to a sticky butterfly. You could feel the
'notchy bit' with the engine off.
Dealer dismantled and cleaned throttle body and problem has
never happened again. Seems there was quite a bit of oily muck
causing the butterfly to stick. No idea how!

This was when the car was standard so there was no overtightening of the
KnN's jubilee clip - although the effect was the same.

P.
Paul

"Seems there was quite a bit of oily muck
causing the butterfly to stick. No idea how!"

It's a function of having to have a closed circuit crancase breather system that requires all engine crancase fumes to pass through the combustion chamber before exiting into atmosphere. IOW the engine has to burn an oily cr-p, some of which doesn't get through!

Rog
Roger Parker

Had a similar problem with my KSeries engine. I let the engine tick over at the rpm I desired then un-plugged the connector to the stepper motor. I have left it unplugged for the last year ....... no problems since.

Russ.
Russell Morgan

Car back from Dealer yesturday to correct this fault.

Butterfly flap checked/cleaned.
Timing adjusted.

Car now purrs. Also, I had the "standard" oil changed from "semi" to "full" (Mobil 1) as the car has now done 6.5K miles. The difference in oil is truely quite astounding!

Tracking re-adjusted too.

Francis

This thread was discussed between 07/04/2000 and 11/04/2000

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