Misfire only when in closed loop? | Ford Explorer Forums - Serious Explorations

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Misfire only when in closed loop?

Chadrax

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August 7, 2010
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Year, Model & Trim Level
97 XLT
1997 Explorer SOHC 6 cyl, 4.0L

Changed: Plugs, plug wires, coil pack. Compression test shows compression within 5 psi of eachother. Changed fuel filter, air filter, cleaned MAF sensor. Ran fuel injector cleaner through.

Checked CKP sensor.

Misfiring on cylinders 5 and 6. Also p0174, bank 2 lean.

Only happens when the car is in closed loop. Open loop it is fine. Freeze frame shows everything fine except long term fuel trim on bank 2, which is at ~ +25%.

What I am thinking is my downstream O2 sensor is faulty, causing the ecm to add fuel when it doesnt need it, causing the mixture to become rich. Either that or something with the EGR valve, as it happens in closed loops.

Can anyone point me in the right direction?
 



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Well I solved the problem. Not sure what it was, was advised to check for vacuum leaks, as the LTFT was +25%. I cleaned the PCV valve, checked all the vacuum lines, zip-tied all the vacuum lines where they make seals with tubes. Cleaned EGR, and supporting components. Problem seems to be fixed, in case anyone else encounters this problem and stumbles upon this thread.
 






Thanks for the follow up. I hope that finals it for you.
 






I didn't know enough to give you any useful advice, but I would like to thank you for posting a follow up. It will help people in the future.
 






I have an egg smell sometimes, but the cc's have been removed?
 






I have an egg smell sometimes, but the cc's have been removed?

I think you posted in the wrong thread by accident. This is the thread talking about rotten egg smell: Link.
 












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