Full rich on bank 2 and full lean on bank 1

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  1. #1

    Default Full rich on bank 2 and full lean on bank 1

    Havingan issue with my 98 cobra, Iíve been chasing it since I bought it. When firstpurchased, it had a p0171 code lean bank one. We checked for vacuum leaks, replaced IM gaskets, etcdid all the grunt work. O2s voltage were good.

    Itook it to the first tuning shop, who after a month apparently fixed it andtuned it. Apparently that O2 was faulty. I get it back and it startedbackfiring on the way home. It still backfires some only in the mornings or ifit sits for around 12 hours. Just recently it started dying on me when I pullinto work in the morning also and It smells like itís running fat. Now itíspulling codes for bank 2 being rich, the egr, and a code saying the pcm wasunable to finish its diagnostic test. I figured it was their tune. When Icalled to see why all of these codes were up and why it was running like this Inever got a call back.

    So Itook it to the second shop powercurvemotorsports. Excellent dude! However when he was logging he noticed that bankone is full lean and bank two is full rich. He said my maf was readingcorrectly. He had an identical cobra same year as mine there and he showed methe dyno for it against mine and Iím down about 50hp and 60torquecomparatively. It feels as tho the engine has a dead miss, however no codesfor it.

    Hasanyone had this issue where one side is full rich and the other is full lean?If so what did you do to fix it??

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  3. #2


    The ECU reads oxygen in the exhaust off the O2 sensor and based on that reading adjusts fueling to bring the mix to what ever the tuner commanded in the tune. If the mix does not get there then the O2 sensor is bad or the problem lies with the injectors. If it is the injectors then you either have a wiring problem or an ECU problem. It is improbable a whole bank of injectors would fail at the same time. You should hope for a wiring problem. Ford no longer offers the ECU.


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