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MG MGF Technical - A Straight occurence ?


Hi all

I have recently dug deep into the old wallet and had moto-build install a new throttle body, K&N filter, performance exhaust and finally new chip and generally i am pleased and amazed the difference it has made to my VVC...

But I am having one small niggly problem that is bugging me and i wondered if any one else has had similar problems either with or without the mods.

If i drive and hold the car in any gear at about 3800rpm i get a small stutter (almost like a plug missing a beat !) Its not constant but if you hold the rpm it occurs from anything to seconds or minutes apart.

This is really noticeable on the motorway as 3800 equates to about 85mph, the speed i generally cruise at
and it does become annoying.... I dont seem to have the problem at any rpm setting and sometimes if you run up through the gears normally you can feel it blip as you pass the 3800 mark...

Any ideas

I plan to unplug the chip this coming weekend and go back to the oem one to see if this could be causing the problem...

Otherwise i think it will be back into moto-build for a complete check up

The car has only done 30000 miles

Any advice or thoughts would be greatly appreciated

Cheers all

STU



S. Dickens

I KNOW I CANT SPELL THE THREAD SHOULD READ:

A STRANGE OCCURENCE !!!

doe!!!!!!
S.Dickens

Stu, I agree, the chip is the likely culprit here. Unfortunately, Motobuild do not have the facilities to correctly set up the chip on installation, so it is using a default setting that is not appropriate for your car.

In fact, it has been known for a poorly set up chip (a superchip Icon unit) to leed to such an inappropriate ignition setting for the exhaust manifold to run white-hot and melt...

The ICON needs to be set up on a rolling road, and the ignition map tailored for your car. Those who've had this done have had no problems with the chip and are delighted with the results.

Until you can get the chip map tuned for your car, I'd recommend that you disconnect it to avoid potential damage to your engine.
Rob Bell

Thanks for the advice

The car generally feels like its running okay, i only noticed this on a trip to the south of france the week before last...

Any ideas where i can get this checked out ?
SDickens

What you might find is with the new TB and the ignition chip advancing the engine is running a bit lean. A Fuel boost value could well be the answer.

For the record, I have the same set-up as you on an Mpi. I'm getting the Boost valve fitted soon. The guys at the rolling road did say the engine was running a little lean, you may find that Optimax help a little..

Tim
tim woolcott

I am having a similar problem on my 1.8i where it feels like it is mis firing but it happens at idle and all gears but seems intermitant and so far have spent approx 200 trying to fix it with diagnostic checks new HT leads, dist cap rotor arm, new crank positioner sensor. spark plugs have only done 10000 miles

It get anoying while cruising when the car starts mis firing, occasionally I have been doing 80 mph and the revs have showed 0 for about half a second and back to normal again. Normally the revs drop about 200-300 rpm when the car mis fires.
It also has eractic idling.

My car is std except for ITG maxogen filter kit and sports exhaust.

Maybe this is linked to a ecu problem but so far has failed to show any faults.

Tom
Tom Randell


Tom

I dont seem to have that much of a problem, in fact when it happens the Tacho just blips, you can hardly see the needle move..its like 1 plug missing a beat, no more than that !

I started running Optimax about 7 days ago but it doesnt seem to have made any difference regarding the problem and i am not yet convinced of any performance gain..

It doesnt seem to be weather effected either, as I considered the leads..

Does any one know if its possible for a plug to have such a tiny intermitent fault, or would it effect the performance even more under more or less load ?

Cheers all for your feedback

STU
SDickens

Plugs, no. Leads, possibly yes as their internal resistance changes with temperature and electrical load.

I don't think that this affects you Tom, but it is sometimes worth remembering that new parts, straight from the box, can be faulty. I had this with a set of K&N spark plugs - appalling running. I had to switch back to the standard type plugs for restoration of normal service. This principle applies to any part that may have been fitted to fix or repair the original problem - and it can be a right royal pain in the ar5e.
Rob Bell

Didn't Dirk have a perpetual flat-spot with (wasn't it) an Icon setup?

I seem to recall he never did manage to get it sorted...


(trying not to sound too pessimistic)

Neil.
Neil

Would underline what Neil said.
Sounds a similar trouble.

Dirk never got the whole truth told from SP (I have still the email BCC:'s at home), but he assumed something about none compatibel firmware releases. Chip not right adapted to the ECU. May be it's what Rob said about only default setup.

I'd go back and ask them to correct before that all gets 'to hot'.

Dieter
Dieter Koennecke

Stu
It sounds like a similar problem to one I had with an old CRX (when Honda built proper cars) years ago. Once the HT leads were renewed the misfire completely disappeared. Probably worth a try.
Neil
Neil Stothert

I have the exact same issue with my VVC and Chip, etc. I was told that the Superchip advances the timing in a few stages up the rev range... At Idle, 3.8K, and about 6K.

Hence the misfire as it further advances.

Paul
Paul


Thats interesting Paul

If its true that could be it, although i cant sau i have noticed it at 6k but i dont generally drive with the engine continually reving at 6k so probably havnt noticed it...

I'm gonna unplug the chip at the weekend to see if the problem goes away or not....

Cheers all for your advice

STU
SDickens

Fuel Boost Valve is going to be the key I think.

I really would recommend you have to chip correctly calibrated anyway. Sanspeed in Bexleyheath is the place I use.

The background.....

I have the same stutter at 3500 Rpm (but only when accelerating not when revs are constant), it's only come on since I fitted the larger TB, so very easy to diagnose (not enough fuel...).

I noticed the stutter after fitting the TTB. A couple of days later I had the chip reprogrammed although the stutter persisted I'm not too worried. The guys at Superchips advised me to go for a boost valve to cure this little problem.

Fuel boost valve is 180quid inc fitting and calibrating.

RichieR (Prior to Nitro conversion) has TTB, ICON, Boost valve configuration.

Tim
tim woolcott

This thread was discussed between 08/07/2002 and 11/07/2002

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