I was driving the other day and the engine started idling horribly. It's really choppy at almost every RPM. The only time it runs normal is at WOT. It hesitates half of the time leaving a stoplight. Its running very rich. I don't have cats and I'm used to the normal smell that comes with the territory, but its much much worse now. I started it up in my garage this morning and it left a black mark on my garage floor.

The truck is a 2001 4.8 with CAI, LTs, and no cats.

Any ideas? I'd like to fix this myself. Mechanics are too expensive for me right now.

-Jim

 

did you ever have the truck re-tuned for the cat delete? i know when i ran my 5.3L with open headers to the exhaust shop it started to idle like crap and run really rich because the rear O2's werent getting any readings, same thing could be happening on yours, theyre just getting the wrong reading because of no cats.

 

No, I haven't gotten it tuned, but a tune is on my list of things to get in a few months. I've been running this setup for 3yrs now. One of the spark plugs was broken and the right bank is running rich. Other than that, I don't know what else to look for.

 

I notice that you have a CAI, is it possible that your MAF is covered in air filter oil? It would be nice to have a scan tool or some software to aid in the diagnostic process. Simple things you can try are cleaning your MAF and cleaning your throttle body, but other than that there are a number of things that could cause it to run rich...

*EDIT* did you swap out the plugs after you found a broken one?

 

also might wanna check and see if you have any vaccuum leaks on the intake itself

 

I went ahead and replaced all of the spark plugs. I haven't checked the MAF. How should I go about cleaning that if it is dirty? A friend of my gf's is a GM mechanic and he's supposedly coming by tomorrow to look at it.

 

Might want to wait for him before you go cleaning the MAF then, but they sell MAF cleaner at most auto parts stores, or you can use electric contact cleaner. Some guys use Brakleen, but that doesn't have a 100% success rate, some brake and parts cleaners leave a residue (even though the can states that they don't), which can throw off the MAF readings...