Fuel Trims going Full Lean and Full Rich on Opposite Banks

[rich s]

I have a strange problem with fuel trims.

I will start the vehicle (2012 Challenger RT 426 w/Whipple 2.9, Manual 6 speed) as the vehicle warms up the left bank (bank 1) ST fuel trims go negative and will max out at -32.8% and at the same time the right bank (bank 2) ST fuel trims will go positive and will max out at 32.8% , if you let the car continue to idle the LT fuel trims on bank 1 will max out negative (-32.8%), LT fuel trims on bank 2 will max out positive (32.8%) and the the engine will die/stop running.

A little bit of back story that might help. Over the winter I changed valve springs and removed the headers to re-wrap them with heat wrap and reinstalled them. I don't hear any exhaust leaks and I don't have any valve train issues.

This past weekend I went to the track. I ran three or four passes to get the fueling dialed in because it was very warm in Florida this past weekend and toward the end of last season it was very cold where I was racing so the fueling need to be adjusted. On the 5th run, all was working well. The supercharger belt broke (I have separate belts for the SC and accessories) at the end of the run. I turned off the track onto the the return lane and that's when all this mess started.

The car would not start until it cooled off - once it started this craziness with bank 1 trying to trim full negative and bank 2 trying to trim full positive started.

I switched ECUs, I switched Throttle bodies, I changed 02 sensors, I changed tunes..... nothing makes a difference.

I am at a loss.

attached is a screen shot of the most recent log idling in my driveway this morning along with the tune.


23-03-31 14-05-09.hplFull Rich and Full Lean.jpg8.12.20-OST-93oct-r6-3bar - read from ECU - with Injector PW data changes.hpt

[5FDP]

I've seen that happen if the o2 sensors harness is routed to the wrong side.

[rich s]

Wow! I didn't even think of that! I will try switching them in the morning. I'm going to be embarassed if that's what it is....

[rich s]

I took a look at it today. The wire harness is loomed in such a way that you can't swap the sides that the connectors for the O2 sensors go to.

Thank you for your feedback!

[5FDP]

That's good to know. It's something that has happened fairly often with people on LS based engines.

[marksrig]

So the o2 sensor factory harness has never been moved at all?

[rich s]

So the o2 sensor factory harness has never been moved at all?

Correct, never removed or moved - the pigtails with the O2 sensor connectors on the factory harness are so short that you can't swap them bank to bank without installing the entire harness backwards. And if you did that, the harness would not reach the ECU to connect to it.

[marksrig]

This is probably a dumb question and it goes against how I know port injection works, but since you had the blower off, is it possible the fuel injector harness banks got swapped?
I mean I know it wont fire the injector in the correct port, but maybe thats the real reason you needed to adust fueling was to compensate for the lack of injector precision.
Just an idea to think on.
I would think it would be back firing and sputtering but I don't know.

[N2speed]

Did this start when you installed the 426? If so cam timing could be off a tooth

[LilSick]

I mean I know it wont fire the injector in the correct port, but maybe thats the real reason you needed to adust fueling was to compensate for the lack of injector precision.

the offsets are stock 2010 5.7

what injectors are in it and where is the injector data?

[rich s]

So this issue turned out to be the MAP sensor.

To answer some of the questions above,

no the injector harness branches weren't swapped, we changed injectors one bank at a time.

no, this did not start when I installed the 426, it's been in the car for several years. the issue occured after the first trip to the track this season.

Edit to post: the MAP sensor was not the issue. See my post below dated 11/25/2023 for my explanation of the fix.

[LilSick]

cool beans glad its sorted

[marksrig]

Could someone explain why the MAP sensor would cause the OP's original problem?

[Fsingh]

After installing the whipple i was getting cylinder 8 misfiring and knock retard at wot. And sometimes car was stalling. Whipple wasn't able to fix the issues. Whipple recommended to drive like this with KR. And told kr wont damage the motor and ecm will put the timing back.

But it was a tune issue. I found a Tuner in Europe. He fixed all issues in first revision . I see big difference in hp and the way it drives now.

[Bullet300]

Jus wanted to chime in for anyone that may be having this issue. I was having the same issue. It turned out for me that one of my coil packs wasn't firing and was not registering as a cylinder misfire. I only found the issue when i went tio gap the plugs in an attempt to make it run right under boost. Moved the faulty coil pack to another spot and it triggered a code immediately. Just an FYI for anyone who might be fault finding this subject as i was when i was having it.

[rich s]

So as a quick follow-up, the issue was not the MAP sensor, the issue was the upstream 02 sensors.

I installed NTK 02 sensors becuase I was told by reputable people that NTK makes Dodge's/Mopar's sensors .

After months of of chasing the problem, I was at a dead end, there was nothing more that I could do or change (alternator, engine harness, coils, spark plugs, injectors, exhaust header gaskets, engine computer, MAP sensor, coolant temperature sensor)

On the odd chance I was at a car show in November and a racing buddy came buy to ask me how my race season was going..... I told him it never started, I've been having an issue since March..... I explained the issue as described in my original post and he says to me: "you know, my wife's Jeep had a very similar issue to what you described, we put MOPAR 02 sensors in the vehicle and the problem went away"

I went home, ordered 2 MOPAR 02 sensors, installed them in the car and bam! problem solved! MOPAR 02 sensors is what the PCU was looking for. I don't know what about them is different than the NTK's or Bosch's, but there is a difference and the PCU only likes MOPAR 02 sensors.....

[f.creek-ranch]

Good that you find the problem.

One thing I have learned for sure....only use genuine sensors, Map, O2, TB, ABS.

It worth to spent the money

[Bullet300]

Just an FYI. I had a similar thing to this happen where one bank was lean the other rich. Turned out to be a failed coil pack.