Idling - hunting from 400 to 800 rpm when cold. Seat Leon

[Volvo--V40]

Hi all,

Car is Seat Leon 1.6 TDI CR Ecomotive, 120,000 miles, 10 reg.

Just recently, and only when cold after being left overnight, the revs when idle jump between 400 and 800 and back again, over and over. Like it's about to stall, then recovers, then stall etc.

This goes on for about 15 minutes until the engine has warmed up, at which time the idling is fine around 900 rpm.

Know someone with a diagnostic tool, and the ECU reports no problems.

From looking around the forum I can see injectors or glow plugs may be the culprit (would have thought they would be reported in the ECU though). Any suggestions?

cheers

[E-bmw]

Your ecu will only report electrical/electronic issues or issues with your exhaust gas mixture with respect to your engine.

It is not your glow plugs because it starts.

[stevieturbo]

You need an operator who can use a diagnostic tool to try and determine any problems, rather than expecting a fool with a cheap code reader to yield anything.

Such problems are not always easy to diagnose, but if the operator isnt experienced and competent with the correct tools....you'll get nowhere.

[Mignon]

There are lots of similar threads online. Usually it's injectors getting old, blocked or leaking. It could be glow plugs if yours are designed to stay on until the engine is warm. If so there may be a temp sensor on the engine which controls this. A bad sensor or bad electrical connection might be preventing this. Usually temp sensors fail by giving a continuous cold signal though hence for example leading to petrol engines running rich not weak when hot.

It may be possible to recode your injectors to increase their fuel output. A diesel engine specialist would be a better bet than an average garage or main dealer.

[Volvo--V40]

Thanks for the advice chaps