Where to start....

This is for my 2005 lx sport. So issue im having is that car starts running lean only after the car is hot and idling after a few minutes. Marty, Jeff and myself have been trying to figure this out remotely for a while now but nothing yet. Car has some goodies installed like stage 2 comp cams, valve springs, MMR heads, edelbrock intake, MMR plenum, 75mm TB, SW lontubes headers and exhaust and a few other little ends here and there. So I am on my secound PCM thinking that was the case but its not.

So at cold starts car starts and runs great. I can drive the car the whole day and not have an issue. But if I let the car Idle for a few after running, my AFR value start making its way up from its normal 14.7 ration to the 20s. Watching my LTFT, seems like bank 2 is at fault. numbers on bank 2 start changing and getting higher. There is no codes present. I have done several smoke test. Done smoke test with engine cold and engine warm. Havent seen no issues. Only smoke is sipping from EGR valve on cold and warm test(beleive this is normal?). I will run the car and let it idle until it starts acting up. I will then redo a smoke test and see if when car gets real hot, maybe a vacuum leak is present. I have cleaned MAF sensor several times and also replaced it with a used one I had in hand with no luck. Unfortunatly, I have not had the chance to datalog when car starts acting up. I will start having my laptop with me going forward.

So, once again, I can run the car all day but when car idles after it gets real hot, this is when it starts to act up and lean out on me with LTFT bank 2 numbers going up.

Advices?

How old are the O2 sensors?

02 sensors are how the car even knows lean from rich ... or from perfect. They will give up in time if used.

I cant honestly remember if all or just maybe one or two O2 sensors were replaced about a year ago.

So assuming its an o2 sensor, why would it only act up when car is hot and after idling for a few? Once the car starts to act up, it will just continue to do so unless car is shut off and let to cool down for a few hours or so.

If I'm not mistaken, the car basically ignores the O2 sensors until they are able to warm up, I believe it just runs off of something like a pre-programmed table for afr and spark timing. Anyway, once the sensor warms up, the computer gets its info for fuel trims from the sensor. I'd swap in a new one and see what happens. People seem to have issues with Bosch ones, myself included, but that was on a non-panther car. I'd go with NGK or Denso, always had good luck with them

and which sensor am I replacing? Bank 2 I understand its driver side. Am I replacing both o2 sensors on that side or just one? one before cat or after?

you mentioned AFR going up. Do you have a wide band installed? Is it in the left side exhaust? I would think so as it's tracking the fuel trim for the left bank. If so, it's probable you have an exhaust leak upstream of them. Even a pinhole in the bung weld has caused my WB to behave the same.
It's the front o2 sensor that the PCM uses for closed loop control. Rear is only used to test condition of the cats.

you probably don't have a bad O2 sensor if my assumptions about your WB and location are correct.

I do have wide band. Ive smoked test the living hell out of this car to many times. I have used few carb cleaner cans aswell with no luck.

I actually just datalogged the car when it was acting up and sent the file to marty. Hopefully he will find something. Also, I smoked test the car again today when car was at its worst hopeing that maybe a vacuum leak was being created when engine was getting hot. There is nothing. This engine is sealed and as tight as it can be. I did find something though.

So I went ahead and checked the car for codes just for the heck of it. Even though I had no check engine light but to my surprise there was a code stored. P0113 which is IAT sensor.

With what I am experiencing, can this be the cause?

and lets remember, the car is running super great all day but if im idling for sometime like in a 15 min car was line, this is where my issue will begin. If I park the car and shut off the engine and let it cool down some, it will run great again.

Smoke test is great for intake side. But I'm taking exhaust leak, which, what happens between strokes, draws air into the exhaust during those times. That air will fool the sensors, wide and O2 into thinking it's lean. Which is why the PCM keeps adding fuel at that point. Like i said, a tiny pinhole, one i could not even see, but felt tiny puffs while running was enough to throw my WB full lean at idle. But under higher rpm and loads make that leak less significant.

I'd look for a cracked exhaust manifold, bad exhaust manifold/header gasket. You can force it to stay in open loop by disconnecting both front O2 sensors. Then it would not try to 'self correct'. See how it runs then.

I had a smoke test down on the exhaust side. had 3 tiny leaks all before the o2 sensors by clamps.

Double check your IAC and make sure it has all the right measurements,I don’t have those handy but I’m sure u can find the info or just buy a new one for maybe 30 bucks and try it out.It sounds very suspicious I’m sure u can clean yours as well,Good luck.

I have the 80mm marauder maf sensor. Ive cleaned the sensor a few times thinking that it might be the issue with no luck. I need to start some where. Being that there was a code stored, I will go ahead a replace the maf sensor with a used one I have put away.

Thanks. This is a good technique that I have used with other situations. I'll try it on the Vic if I can get my hands on the O2 sensor connections.