stutaeng
I'm Awesome
...still cylinder #2 per original post?
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Which cylinder(s) are misfiring?
Per my post #2:
"It's pretty easy to do a good guess if it's a vacuum leak or something else. Rev up the engine and see what the fuel trims do."
If your LTFT is 25 at idle, but lowers (or improves) as you increase the RPM, then look for vacuum leaks. If fuel trims don't change much, then not likely vacuum leaks.
The reason is that the leak is a larger percentage of the metered air going inside the engine. As the engine RPM is increased (and so does metered air), the leaked air stays relatively the same, so the ratio is improved at higher RPM.
It's weird sometimes on the fuel trim codes. A few weeks ago I was helping my nephew diagnose his 4.3 Vortec S10. The thing was running like crap. Had a hard time restarting when warm. One bank was running like 50 percent rich, but no rich codes!
We hooked up a fuel pressure gauge, and the pressure went from like 60 to almost zero in 30 seconds. Either an injector was stuck open or the FPR was leaking.
He got a new spider assembly (comes with a FRP) and it runs smooth again.
Another development...
It's acting like it's vapor locking. It cold starts fine, but this morning I stopped to get gas and it wouldn't start up again. I had to let it sit for a while then when it did finally start it was a rough start. Once driving though it was back to normal. It's done this a few times now.