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MG MGF Technical - Fast idle and engine cut out

The past few times I have driven my 2000 1.8i F, the engine has idled at 1500rpm when the engine has got warm (say 15 to 20 miles into journey).

Today, it happened again on first journey of 28 miles. I then drove 35 miles, 10 miles, and 20 miles with no problems. Then, on my final 15 mile journey, the revs dropped to 0rpm and the engine cut out every time I put the brakes on - particularly dangerous on fast a-road roundabouts.

The car started again each time and I tended to 'engine brake' as far as possible to stop it cutting out again.

A quick search on here would suggest TPS troubles. The car is due a service, what shall I suggest to the mechanic to look for/adjust.

Many thanks

Dave
Dave Ellis

Hi Dave:
I had same problem a few weeks ago, just two months after I changed the battery, red cable was cutted and in some ocassions was touching the metal body, cutting out the engine unless I kept my foot at the pedal.
You could check the battery main cable (red one) to discard a short circuit possibility.
regards.
Eduardo
Eduard Miro

High idle speed on a warm engine is often due to the ECU not getting a correct engine temperature reading, either from a failed sensor or perhaps a bad connection on the wiring. If you disconnect the sensor (brown one just off the end of the cylinder head) while the engine is fast idling and there is no change to idle speed, than that is the culprit.

Having said that, a failed sensor wouldn't normally cause the engine to stall on braking, so there could be a problem with the TPS or as Eduardo says, an electrical short. Worth unbolting the negative-to-body cable and checking for corrosion - a poor connection here can cause a variety of behaviours.

In the meantime, it's a good opportunity to develop your heel'n'toe technique, just in case you ever take your car on a track day ;o)
bandit

Cheers for the replies, I shall try and check it out over the weekend.

As for the heel 'n' toe, I'm no way good enough a driver for that... was tempted though!

Dave
Dave Ellis

Oh PS, I bought the car off my dad recently and he had the ECU replaced last year so it probably is not a failed ECU.
Dave Ellis

> had the ECU replaced last year so it probably is not a failed ECU.

That's an important hint on probable failure with the ECU and harness mechanical installation, resulting in intermittant connection problems atz the ECU connector.

Assume the harness wasn't attached correct and applies pull force on the connector spades.
There should be a cable tie (Ty-rap) attached at the lower edge of the ECU, holding the harness *force-free* (spelling?).
The cable must leave the the ECU connector in a smooth curve.

See the images on this site
http://www.mgfcar.de/starter/start.htm
(Ignore the header description, it's about another problem, but the pictures show the problem I reffer to.)

http://www.mgfcar.de/mems1.9/harness_loose_sc02513.jpg
and
http://www.mgfcar.de/mems1.9/connection_Dsc02514.jpg

Worth to check.

Dieter

Would concur that it is probably an electrical problem. Perhaps it is time for us to include an 'Electrical Connection Clean' with the cambelt change.
If you need to know < what shall I suggest to the mechaic what to look for/adjust > then it is time to find a new mechanic.
Geoff F.
Geoff Farthing

Thanks for your help, it's booked in for service and MOT on Thursday, so I'll let you know how I get on.
I am new to the area so know nothing about the garage I am taking it to. The reason I asked the question is to have some idea what the problem is; better to go armed with a bit of knowledge than appear to be the mechanical novice I am!!
Dave Ellis

This thread was discussed between 04/02/2009 and 10/02/2009

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