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09-16-2011, 07:38 PM #1
- Join Date
- Aug 2007
- Kirkwood, Mo
1996 Tahoe irratic misfire at idle, runs fine off idle and cruise
I am pulling my hair out. I have been having this issue on and off for about 3 years. It did not start until I was in small town and put Kroger's gas in it. It would usually clear up for months after a can of Seafoam ran through the tank. This time it came back and I put in the seafoam and it kept doing it. Then I ran some seafoam through the brake booster hose and fogged it. This only made it worse, I could feel it misfiring on the highway. I had my father-in-law drive it, he is an old school wrench and racer, he thought it might be a vacuum leak. I checked it over with propane and could not find anything. I decided to create a vacuum leak and pulled the pcv hose. The engine picked up a couple hundred rpm and smoothed right out. Hmmm, must be rich. I pulled the plugs and found bank 1 was black while bank 2 was a nice toasty brown. I verified the gap, cleaned them and put them back in on the opposite bank. They are OE AC double platinums. Then I cleaned my K&N filter, the throttle body and replaced the pcv valve. This all seemed cut it down by about 70% but it was still there. So based on all of this I gave it my best guess and replaced the CPI with the updated MFI figuring the poppets or tubes were leaking or clogged. This was last Friday. Friday night it acted up and again Saturday morning so I swapped the 02's to see if the O2 was causing it and then it was fine until coming home from work yesterday. Through all of this I have been driving around with my scanner hooked up and the only thing I see is the fuel trim getting turned up to the max on bank 1 and the O2 going lean. Bank 2 never shows an issue even after I switched them. I cannot locate any vacuum or exhaust leaks. I have checked the distributor and do not feel any play. The cap, rotor and wires do seem to be an issue. I even hosed it down and there was no reaction. The lower intake gasket was replaced a couple of months before the problem originally started. I see other's with the same issue on the net but there are no answers.
P.S. I have not changed the fuel filter but it is next on the list. It is currently soaking up some PB Blaster because I could not break the lines loose. However, I would think if it was a fuel supply issue it would affect both banks.
Last edited by tankdg1; 09-16-2011 at 11:40 PM.
09-17-2011, 07:11 PM #2
Just wondering, how old and how many miles on fuel filter?:cool:
2005 Chevy Silverado Z71 Crew Cab
6" Skyjacker lift w/Edlebrock dual front remote resoviour shocks, single rear remote. Rancho skid-plate.
17" x 9" M/T Classic Lock Wheels, 35" BFG A/T or M/T tires
4.10 PercisionGears w/factory locker, T/A Performance rear-end cover
Banks CAI intake, ported throttlebody, JBA coated headers, over-sized Magnaflow cats, Magnaflow cat back exhaust, Diablo tuned
B&M aluminum deep transmission pan
Warn brush guard w/Warn 9.5 XP winch, PIAA bulbs, Line-X bedliner, AWS Black tool chest, Extang tonneau cover
Weather Tech floor mats
Cover-Craft seat covers
Dash mat cover
Formula One window tint
One black Lab in rear seat.
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