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[steve6367]

Andy,

Thank you, was just slightly disappointed.

I will try and get some live data up on here from while it is lumpy. Unfortunately my laptop based system does not allow fuel trim reset only switch of service lights. I guess the trim could be out with all the running on wrong MAF? Any benefit in going for a motorway run or will it take hundreds of miles for the long term trim to adjust?

Thanks again

Steve

[CaptainZok]

Correct me if I'm wrong but doesn't disconnecting the battery reset the fuel trims?

[steve6367]

If it does I can do that, I have readio code to reset that.

Steve

[steve6367]

Ok so I went for a drive - more of a crawl by the end before it died completly. By the end of the drive before it stalled, the short term fuel trim was up at 25% (from 11%) and now it simply wont start.



While is was working gear changes and other data looked ok - does 25% mean it is trying to make the mixture very rich?

Steve

[CaptainZok]

Not an expert on live data by any means but I'd have thought 25% trim meant the ecu was trying to put more fuel into the mix.
Could there be unmetered air getting in there which the system is trying to compensate for, which may explain why the previous maf was flagged as faulty?
Have you tried spraying carb cleaner around the engine to look for air leaks?

[steve6367]

Not tried with carb cleaner, I will have a go if I can get it to run.

Thanks

[steve6367]

Todays update - battery disconnected for an hour, but long term trim stays at -12.5%.

Started (just) and running very rough - this is a cold start and so in open loop, does this mean it is not using MAF / Lamda etc? Getting worse as it runs (30 seconds), so I switch it off before it get warm enough to get to closed loop.



Steve

[Andy H]

I have not got any experience of the 2.2. Does it have an EGR (exhaust gas recirculation valve). I seem to recall discussions about how they can stick open and cause rough running (but don't know if you even have one )

Really need The Boy or Kevin Wood to give some input here.............

[steve6367]

Andy, thank you I will take a look and see if it does have one.

I have put the old MAF back in now and it does run properly at least which has allowed me to check for air leaks - can't see anything though.

So I am not sure what is happening now! Do I have 1 wrong MAF and a a correct but faulty one? Or some underlying problem that I dont understand?

Steve

[Andy H]

Does your scanner allow you to see the 'long term trims'?

It seems to me that your ECU has learned from the incorrect MAF and has saved way out settings for the long term trims. You probably have the correct MAF now but the ECU is applying the (wrong) long term trims.

I think you need to get to someone with Tech2 and try fitting your new MAF then reset the long term trims.

[steve6367]

Yes long term trim is at -12.50% - The known good Omega 2.2 I tested had a long term trim of +11.72, so very different to mine.

Maybe time to make it work with wrong MAF and take a trip to see Kevin as you say.

My only other thought is that it does run so long as you keep going with new MAF, so if I went for a decent drive when its quiet will that change the long term trim, or is it calculated over thousands of miles?

Steve

[Andy H]

Todays update - battery disconnected for an hour, but long term trim stays at -12.5%.

Started (just) and running very rough - this is a cold start and so in open loop, does this mean it is not using MAF / Lamda etc? Getting worse as it runs (30 seconds), so I switch it off before it get warm enough to get to closed loop.



Steve

Sorry - wasn't paying full attention to all the information in front of me.
Long term trims should be (are?) stored in non volatile memory (so they don't get lost when battery disconnected).

If the "wrong" MAF was for a much smaller engine it probably gave a linear reading up to (say) 1/2 of your engines maximum mass flow. After that it couldn't give a larger reading (because it was already at 100%). Your ECU has probably learned that the "wrong" MAF is exaggerating how much air is flowing so has applied -12.5% long term trim to try and compensate. Driving around on small throttle openings is probably OK but any time you open the throttle and get more air than the "wrong" MAF can cope with will mean that the ECU isn't aware that more fuel is required.

Fitting the correct MAF now means that the car is undriveable once it warms up because -12.5% is far too lean. It probable starts OK and runs OK until the engine is warm because of the cold start enrichment

Definitely get Kevin on the case if he is available

I still worry that there may be something that caused the original owner to fit a new (wrong) MAF that hasn't been identified yet. If you are lucky the original fault was correctly identified as being the MAF but incorrectly fixed with the wrong MAF.

[steve6367]

I have not got any experience of the 2.2. Does it have an EGR (exhaust gas recirculation valve). I seem to recall discussions about how they can stick open and cause rough running (but don't know if you even have one )

Really need The Boy or Kevin Wood to give some input here.............

Fingers crossed they see it soon then :-)

[steve6367]

Kevin or The Boy did have any thoughts, people keep suggesting your the mostly likely to know about such things :-)

Any thoughts much appreciated.

Steve

[steve6367]

Update - I had the learned values (including longterm fuel trim) reset  this afternoon, fitted new MAF again and the car runs well.

Clearly time will tell, but initially its looking good :-)

Thank you for the advise Andy.