[rcoe]

Was running great until about 2 weeks ago, started having a bit more chop at idle and lamda was running very lean (1.2 -1.35) at and just up from idle, but when driven harder it really smoothed out WOT was fine .82 - .83 right where it is set to.

Thought I had it fixed last week but now I can't really even drive it as part throttle is so bad.

To me it seems like when it is running in closed loop something is very off and it is running very lean and in open loop it is good.

Going to swap out the O2 sensors to my last known good ones as the last change I did was take out the cheap ones to replace with OE ones and pull the secondary ones as they have been programmed out.

I was also thinking like many it was some kind of intake leak but I did spray every part of the intake with starter fluid and could not get even a blip of change in rpm.

I am about to tap out and bring to a shop, not something I like doing but this thing is kicking my butt.

[jlaudio11]

So I had something weird happen the other day at the track when switching tunes in the E92 ecm. The car started and died, then restarted and was running very rough. I hooked up laptop and stft's were maxing out and my wideband was reading very lean, I reset ltft in vcm scanner and kept driving it up to staging lanes and all of a sudden it got back under control and normal. Stft's went right back to a few percent here or there. I'm still not sure what happened, it had never happened before and hasn't happened again.

[rcoe]

Originally Posted by jlaudio11

So I had something weird happen the other day at the track when switching tunes in the E92 ecm. The car started and died, then restarted and was running very rough. I hooked up laptop and stft's were maxing out and my wideband was reading very lean, I reset ltft in vcm scanner and kept driving it up to staging lanes and all of a sudden it got back under control and normal. Stft's went right back to a few percent here or there. I'm still not sure what happened, it had never happened before and hasn't happened again.

Interesting. Worth a try.

Thanks

[CamOnlyJabroni]

Originally Posted by rcoe

Going to swap out the O2 sensors to my last known good ones as the last change I did was take out the cheap ones to replace with OE ones and pull the secondary ones as they have been programmed out.

When I had a bad O2 in my ZL1 the car would run fine until it went into closed loop but the fuel trims would go way out with a big split from bank to bank. Car would go very rich and very lean in my case. Had a hard time idling especially in gear at a stoplight.

[rcoe]

Originally Posted by jlaudio11

So I had something weird happen the other day at the track when switching tunes in the E92 ecm. The car started and died, then restarted and was running very rough. I hooked up laptop and stft's were maxing out and my wideband was reading very lean, I reset ltft in vcm scanner and kept driving it up to staging lanes and all of a sudden it got back under control and normal. Stft's went right back to a few percent here or there. I'm still not sure what happened, it had never happened before and hasn't happened again.

Got home put the MSD wires back on. Before starting it I did the stft reset with the key on. Fired it up and could tell right away it was running better and lamda was sticking right around 1.0, where yesterday it was hanging around 1.3.

Was just going to move it over to the other side of the garage but backing out it was acting like it was back to normal so I took it around the block and everything from idle to a gentle pull was great. Even idled great for 5 minutes when I got back.

So WTF is this thing just messing with me? I do have before and after logs if anyone wants to look at them to help me figure out what is going on.

Thanks for the winning suggestion JLAudio11.

[jlaudio11]

Originally Posted by rcoe

Got home put the MSD wires back on. Before starting it I did the stft reset with the key on. Fired it up and could tell right away it was running better and lamda was sticking right around 1.0, where yesterday it was hanging around 1.3.

Was just going to move it over to the other side of the garage but backing out it was acting like it was back to normal so I took it around the block and everything from idle to a gentle pull was great. Even idled great for 5 minutes when I got back.

So WTF is this thing just messing with me? I do have before and after logs if anyone wants to look at them to help me figure out what is going on.

Thanks for the winning suggestion JLAudio11.

So when I first started tuning my car after adding the turbos and thus changing the inlet pipe and maf setup I accidentally induced a situation where I had it so rich it was reading lean. I had to take a step back and say there’s no way this is correct and somewhat start over. I think something like this is what happened to you and me. It’s so rich it reads lean and the stft just keep trying to add thinking it’s lean and prolonging the situation. It’s why when I saw crazy high stft my reaction was to reset it. Why it goes rich/shows lean I’m not sure. I’m thinking a weird reading on startup is what starts the process and it can never get out of it. Somebody else might have a better idea but that’s just what I’ve seen in my experience.

[Zracer]

Raw fuel/ like if you have a plug not firing will not read on afr gauge and will show lean . I see this on the Dyno at times. I'm still learning this Lt platform but I'm very familiar with LS platform .

[KingLT1]

Rich sent me a couple idle logs to look at. When his car is having this issue the o2 sensor readings are locked full rich and not switching properly. The short-term fuel trims are -15 to -20 when this happens. Similar to what I had seen earlier this spring before he replaced the sensors. After the reset now everything looks better.