Can anyone help me out? My car is a LS2 408 stroker build and iv been chasing down what seems to be a pretty annoying issue. My car will start up just fine and idle for a little bit but all of a sudden it'll kinda start acting finicky and idling really rough as if it were about to stall out but usually catches itself at idle. Sometimes it takes a few minutes for it to act up and sometimes it happens right away after starting. Doesn't matter if it's hot or cold...

Also while driving the car there is no issues under decent or heavy throttle, but whenever im in over drive and cruising around 50-60 mph you can feel a "trailering" sensation as if the car has a misfire, whenever I feel the miss I can see the AFR gauge spike to 20 and then as soon as it stops it comes back down to around normal. This happens every few seconds or so while driving.

And another issues is when backing up and putting the car from reverse into drive it'll stall out too. I have noticed that this issue only occurs when the car is under a light load and low rpms' it runs just fine under good throttle.

One more thing Is that if you back up or in drive at idle and even going up a slight Incline like a driveway or something the car will pretty much stall out as well. On a flat surface it's usually fine.

Also while driving sometimes it'll be just fine but if I come to a light or stop the car will again act up and sometimes completely stall out or catch itself. I found that if I put in in neutral the rpm's pick back up and I can usually save it from stalling. All of these leads me to believe it's a vacuum leak/ fuel injectors ect.. I just don't know. I know it's not the iac because I tested it. The shop I had it at before said that they have never seen an fbody that acts like this with no observable issues on the data and tuning. I find that hard to believe but idek. Any help would be appreciated!

 

do you have the ability to data log and post a log of the issue reported or your tune?

 

Unfortunately I do not, the shop I had it at had all the software running and hooked up and said it wasn't showing anything apparently? Maybe I misheard but they werent positive what it was. There are no codes or check engine lights either.

 

Your AFR gauge showing super lean indicates that at least cylinder in that bank is not firing, either because no spark or too lean to fire. Concentrate on that bank; consider a sticking injector, bad coil(s) or bad connector to the injectors or coils.
If you have headers, use a IR thermometer (e.g. $20 at HF) to determine which cylinder(s) are firing less.
BTW - This is a good example of why a wideband AFR gauge is useful; personally I have one for each bank.

 

Thanks, I didn't think of that, that's a good idea. I'll definitely have to try it out.

 

O2 sensors could be worth looking at

 

I thought that too, but it's brand new so I figured that would probably not be the case. Unless it's faulty...