Anyone any idea what would cause this? Most often on startup (cold), and when the engine is over 80'C. Idle creeps up (takes about 3-4 seconds) to about 2k, sometimes stays there, sometimes drops to normal. The brake pedal puts a stop to it, until released, where the idle goes straight back up.

Its doing my head in.

I would suspect either the TPS or the IFI computer. Might make certain the TPS is returning to idle postion; spring might be getting tired.....

Neither is as cheap as keeping your foot on the brake while idling though.

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

What's the IFI?

I think we may have established that your car doesn't have an OBD port, right? If it did you could monitor the TPS and see what the readings were. I'd suspect it is the TPS and hitting the brake overrides it. If you can't monitor it then there are some people who claim to have had success cleaning them.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

It does indeed have an OBDII socket. I can't see any way of getting in the TPS (which is surely just a potentiometer), so perhaps I should buy a code reader of some description?

Which would you recommend?

If you have the OBDII port then any good reader with the ability to read individual items will work. Buy yourself a scangauge II and then you can monitor many engine functions including TPS and MPGs while you drive.

As far as getting into the TPS - they are not designed to be opened, right, but you may have to break it open and then find a way to reclose it.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

I'm checking around for some scrappers. I saved £200 by getting a replacement duovalve from a scrapped W210 just a few weeks ago. If I can get a TPS for £10 or thereabouts, and if it fixes the problem, I'll break the old one open so you can all have a look.

I'll bet you will find one out there...now that our cars are getting older there are more and more of them in the scrapyard...good luck!

Have you checked the plug at the TPS to see if it is nice and clean? It could be as simple as corrosion on the contacts at the plug at this point.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

Good one, I'll do that.

One day I'll find a silver W210 that doesn't have rusty wings, those wings will be mine And the driver's seat. And the fuel shutoff valve. And the viscous clutch. And the nearside rear parking brake. And the driver's handle IR receiver.

*thinks hard about what else doesn't work properly*