hi guys hope you can help...

The check engine light is on and throwing P0172 code. The Long Term Fuel Trim on Bank 1 is at -26.6 before i even start the car and is at about -20 to -27% at idle and drops to -10.16% (static until the revs drop again) above about 1500 RPMs. Car seems to run great but did used to throw the dsc light on after spirited acceleration. When I read the ecu I had a p0108 code so cleaned the tmap sensor and that seems to be cured, but still got the quoted symptoms as above. STFT is ok on idle and goes nuts when the LTFT raises to -10 (drops right down to like -18 to -27%), O2 sensors seem to be reading ok, and coolant temp and intake temp seem good too... so I'm left with looking at FPR and injectors (maybe plugs, leads and coil pack)

Looked at the figures on the scanner but don’t have any base numbers if anyone can help?

One thing that stood out was the intake air temp was at 10-11°C with ambient temp of 7°C... engine had been running as it was on the bypass, ECT was a steady 89°

Also, the trims seemed to be ripping out about 25% in total to lean it off, -10% LTFT and -14% STFT throttle position was quite a light load so not accelerating, just coasting

Here’s a few shots from the drive home earlier... 1&2 are from cold, 3 is mid run, 4 is the panda under constant load up a hill and 5 was at idle at lights nearly home, so engine temp was 89/90 (removed as I know that’s usually spot on and wanted the throttle on the same page)
readings before i switched on the engine
engine off part 2
mid run home @ 50ºC
O2 sensor under light load
at 89/90ºC on idle at traffic lights
See the inlet temp is quite low? And I’m not sure about the map pressure as, as I said, no point of reference

Any ideas anyone?

i also thought i had I had an issue where I was burning oil at a tremendous rate (like a litre to 250 miles) but with no smoke at all. This seems to be improving, strangely, and whilst it's still doing it to a lesser degree, I have noticed a leak again on the rocker box after doing it not 3 months ago... as an outside chance, would a dodgy Pcv valve cause anything like this? I've done the glove test and at idle there's a vacuum as it should be, but not checked off idle

any help gladly received

thanks
Martyn

 

 

What do your spark plugs look? If they are showing signs of being overly rich then you are right to ignore the O2 sensor. If they look lean, then it is likely that the O2 sensor is artificially pulling fuel out and creating the lean condition.

And where you mention the STFT going crazy when the LTFT is high, that's because the LTFT is actually the moving sum (integral) of the STFT.

 

thanks for the reply... the perculiarity is that over 1500 rpm its like a switch for the LTFT. it goes to -10.16 and never fluctuates, whereas the STFT does, dependant on driving conditions... surely after a prolonged run at a certain STFT load (say, -15) the LTFT would adjust to keep the STFT at or around zero? but it doesnt.. it seems rev dependant rather than learning dependant, if that makes any sense?

 

 

in a thread revival, I thought id update... shows how much the car gets used lol

after much deliberation I puled the fuel rail to inspect the injectors for leakage at idle... no dice. so then I, for whatever reason, decided to remove the FPR... to my amazement I noticed the little O ring on the neck missing, which I'm gathering means it was running at full pressure pretty much all the time, hence the mega-rich mixture at idle which got slightly better as the revs and load rose.

so now im at a place where the LTFT is 'only' stripping out about 9.4% at idle and it never seems to move from there no matter the engine conditions.. I checked adaptations and they are sat at 9.5% so I guess I need to get them reset? when the ignition is on but not engine running, the LTFT is still sat at -12.5% even tho there is no fuel to inject and its in Open Loop running (because it isn't lol), so I think that's its base and it is working from there?

good theory?



Ill get to the oil burning later.....