I recently bought an 01 QC 4x4 with 5.9(110,000 miles). The problem is it starts right up and idles fine for about 2 mins then I can hear it really try to suck air then runs rough for about 2 mins then after that it smooths out and its fine again. Has done this since the day I got it about 2 weeks ago. Previous owner did a tune up before I bought it thinking it would fix the problem but obviously didn't. I'm gonna fix the plenum this spring but until then I was hoping I could get it running alittle better. Previous owner also removed cat which is why I was thinking plenum bad, clogged cat, bad front sensor. Any help is appreciated.

 

Sounds a lot like a failing O2 sensor......

 

I'm with the ninja HeyYou.. also, some folks report a sound that sounds something like a howl when the o2's aren't good right after start up..

 

Now that you mention that howl, I think I might hear that too. Thanks guys for the help. Only thing is if I replace it now its probably best to do it again after the plenum fix right?

 

Yes and no... depends on how long it takes you to repair the plenum. Without the back pressure from the cat, it won't see the oily exhaust for very long, so it might be alright for a little while. Just take it out, inspect it, and use your best judgment to determine if it needs replacement again.

 

Sounds good, will replace when I get some decent weather and give the results, thanks again.

 

Well I replaced o2 sensor with ntk one from napa and no more problems running rough. Thanks again