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[Davey]

Getting this error, but only when cold.. The O2 sensor has been replaced. My money at the moment is on a clogged fuel filter but we havent tried that yet..

If I reset the MIL light once its warmed up the light doesnt come back on, but when you start from cold after a 100 meters or so on she comes!

Any ideas ?

Cheers!

[ians]

That's a new one on me.  Does the handbook give you any clue?

Where are you in Berks by the way? I'm between Reading and Newbury.

[Davey]

I'm in Woodley..

[ians]

Fuel filter is pretty straightforward to replace (on saloon ) so well worth doing that if its not been done for a while.

[Davey]

Yeah ive done tons of them first on my list of things to do.. before going mad replacing everything under the sun  

[Kevin Wood]

Fuel trim is the adjustment of the fuel mixture made by the ECU to get the Lambda sensor to read the correct oxygen level in the exhaust. In this case it has gone outside the allowed range of adjustment which means either the Lambda sensor is lying for some reason, or the metering systems on the car are not giving an accurate base fuel mixture.

Anything that's likely to change the base fuel mixture of the engine before the correction is made can cause this as well as a faulty Lambda sensor.

So, clogged fuel filter a possibility - can't harm to change it if it's old, although I'd expect fuel trim to be high in that case :-/

Other things to look for are air leaks in the induction system, clogged air filter, faulty MAF, dirty throttle bodies and exhaust system leaks upstream of the Lambda sensor.

As it's temperature sensitive, Possibly the intake air temperature sensor and coolant temperature sensors...

Kevin

[Davey]

Was thinking CTS.. its another cheap fix to try.. It does run a little lumpy at idle but not enough for alarm bells to ring.

Will give the inlet temp. sensor a squrit with clear and the MAF... I've got another Omega I can pinch a MAF from to test.. Exhaust sounds solid, will remove the manifold cover and check for cracks though.

I think CTS and Filter are first on the list

Does the inlet temp. sensor actually get used from a cold start?

[Kevin Wood]

Does the inlet temp. sensor actually get used from a cold start?

I would imagine so. It's used to correct for the density of incoming air so it should be used at all times. the correction is pretty small, but might just be enough to tip it :-/

Coolant temperature will obviously determine the enrichment used at cold start - does it start OK? It will also probably be used to determine when closed loop running starts, as it won't close the lambda correction loop until the engine is at a reasonable running temperature. Could be that it's running closed loop when still warming up due to a lazy coolant temperature sensor?

Worth trying a swap of each of these if you've got a donor vehice handy.

Kevin

[Marks DTM Calib]

There is no seperate air temp sensor on the 2.2.......and air temp has minimal impact on mixture anyway on MAF based systems.

[Davey]

Sorry I wrote the wrong error it was "Fuel Trim Malfunction".

I removed the MAF and inlet pipes tonight, cleaned the MAF and the throttle, then refitted.. Cleared the MIL light with my diagnostics and took it out for a few miles.. No light fingers crossed it was the culprit..