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Old 01-22-2010, 06:22 PM   #1
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extremely rich on decel only, but the MTF is good

Just so everyone knows this is cross-posted on the racer support forum and fj because I am dumbfounded and fed up with this issue.

Not quite sure if this is a tune issue... or a mechanical issue with the purge canister or purge valve... But it has been happening for just over a year on several different tunes, injectors, and MAF setups.

Its a 2002 Focus with code NFC1. Manual trans swap is done, so the ECU is forced into neutral gear at all times.

My MTF is well and good. At idle, steady-state, or other normal operation not recently after this rich issue, for anything from 140-350cts it trims within 2-3% of 1.

Yet for some reason, whether the car is in gear or not, when I let off the throttle while moving the wideband will go to 12's or sometimes 11's, and STFT will just climb all the way to 1.25. Sometimes it starts to trim around 1.20, but usually it will just peg. If I let it idle for about a minute, the trims will come back down slowly.

Some of my theories:

1. I have tried datalogging CFSO and it is NOT entering CFSO under any circumstances, even though everything related to CFSO in the tune is stock. Does it need to go into CFSO to avoid going rich? I don't think this is the problem since the issue will happen whether or not I am in gear. Will it only do CFSO if it thinks the automatic trans is in gear? If this is not causing the problem, I will have to make a separate CFSO thread later on to figure out why its not entering CFSO.

2. I have 42lb injectors and the value file is checked good against my MTF with stock fuel injectors. But I'm wondering if its riding on the minPW? I believe its set at 0.0004 or thereabouts. This is not logically the problem however, since in normal situations both in and out of gear it will run at 140 maf counts trimming around 1.

3. Mechanical issue with either the purge canister or purge valve. The car has 199,000 miles on it, so this would not be out of the question. How do I test these components? I was thinking of unplugging the vac line from the canister (and plugging the line of course) and seeing if it still goes rich on decel.

Any other things I should be looking into? Like I said, everything related to CFSO and the purge canister is all set to stock values.

Also if anyone wants to see my datalogs, I can post those up no problem.

Thanks for reading :)

Originally Posted by Dennis_Grant
Remember this list: Bilstein; Penske; Koni; Ohlins; Sachs; Dynamic Suspension.

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