Rough idle, still

elgineddie · April 20, 2005

Howdy team,

I've been reading thru tons of posts I've searched and still can't seem to find anything that matches my problem. My 2001 K2500 6.0L 'Burban (100,000 miles) has a rough idle. Runs fine on the road and gas mileage isn't that bad but when I'm at idle, either hot or cold, it feels like I've got a lopey cam installed. (Well, not that bad but it's a bad idle, period!) Starts fine and runs fine otherwise.

I've checked fuel pressure and it's within specs. The fuel pressure regulator is dry. I have new plugs and new wires. I'm running a Granatelli MAF but I swapped in the old one and the idle is still bad. I cleaned the IAC and I Sea Foamed the intake but no luck.

There is NOT a MIL lit but when I pulled the codes, there were 2 pending: P0171 and P0174. My book tells me it's lean on banks 1 and 2. What the heck does that mean?

I just checked the vacuum and it's OK until I rev the engine and it comes back down and almost dies. At that point it's at like 8 or 9 hg and slowly creeps back up to 15. In my manual that diagnostic points to a probable exhaust blockage (clogged cat?).

Many thanks in advance for any direction or advice you can share!

JCedar · April 20, 2005

Mine had the same codes when the temp dropped to -10F here in the U.P. it turns out both of my O2 Sensors behind the catalytic converters are shot. I actually just ordered them off of GMpartsdirect last night for a HUGE savings. My dealer tried to charge me $125 a piece and I said NO WAY, so he gave em to me for $105 which came to a total of $222.60 with tax. Then I went on to gmpartsdirect.com $62.65 A PIECE. That was nice to see, so earlier today I took back the O2 sensors I bought from the dealer. I have a somewhat rough idle, and my gas mileage has been down quite a bit lately, and you could actually hear the O2 sensors rattling, I thought it was the Cats but it turned out to be the O2 sensors busted up internally. The part # is 25312201, and the total from gmpartsdirect was around $150 for both with shipping, that would be my guess as to what it is!!! Anyone else have any ideas???

Have a good one!!

elgineddie · April 20, 2005

Thanks JCedar!

I am thinking it has something to do with either the O2 sensors or the injectors. I am about "this close" to ordering the Westers matched/flowed injectors and their PCM this afternooon. I guess another $150 on O2 sensors won't kill me. At least when this is all over I'll have new parts, a killer Westers tune AND rough idle!!!

Please keep the ideas flowing if anyone has any to share.

Ed