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Rough idle, still

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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!

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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!!


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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.


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