Mechanics

CHEVY ROUGH AND UNEVEN IDLE ON COLD MORNING

2002 Chevrolet Silverado

Engine problem
2002 Chevy Silverado V8 Two Wheel Drive Automatic 63000 miles

Thought I had bad gas, never did it before, just in morning on cold 30% nights, morning start ups, engine would start, high idle at 1000 r.P.M, then idle down to700 or 600, after about a minute or so it will idle rough, somtimes idle down to 300 to 400 r.P.M, sometimes activating check engine light to flash but not stay on steady, after five minute warm up, it will clear up, runs and accelerates great, after sitting all day, a start up in the late afternoon somtimes but not all the time will do the same rough start up. Have put new vacum solinoid on and cleaned inside throttle body with cleaner still have problem. Been working on Chevys for 35 years having problem with this one, Hope I won't have to go to$ 100.00 per hour GM shop! Could it be throttle sensor or other sensor on throttle body? Jack Ski
Avatar
Jackski
January 30, 2008.



I had similar problems and my intake and throttle body gaskets were leaking. Also my MAF sensor was bad from over oiing my K& N. Changed them out and my truck runs great and the check engine light is gone.

Tiny
Asirmans
Jan 30, 2008.
Warmer weather has set into Delaware the last couple of days, truck starts much smoother now with almost no noticable r.P.M. Pulsating, did not change throttle body gasket or MAF, do you think it might be somthing other than gasket or MAF? Oh, yea what is the K& N you mentioned before? Thanks. Jackski

Tiny
Jackski
Feb 7, 2008.
Well, her we go again, 13 degrees this morning, started truck, trucks r.P.M went soaring up to 2000, as cold as it was I thought it was going to throw something! Came down to 1500 then 1000 in about 30 second, r.P.M.S shuttered from 700 to 400 while in gear! Ran rough while in gear at stop, finally after 20 minutes of running idle cleared. What sensor could this be? Jackski

Tiny
Jackski
Feb 11, 2008.
Got this info from a service writer at GM dealer also from owner of local repair shop in business for 30 years both reliable old friends, they claim this problem is the intake manifold gaskets that are leaking, when cold they contact enough to suck in air leaning mix to point both bank one and two 02 sensors activate, makes sence since when warmed up motor smooths out, check engine light comes on, but does reset after two or three cold start ups, they also claim you must use GM gaskets to assure upgraded thickness, $101.00 compared to other brands at $30.00, $60.00 and $70.00 ones! Going for it this weekend, let you all know how it goes after I take it to clear obd computer!

Tiny
Jackski
Feb 14, 2008.
Good old autozone said, lean bank 1 and 2 02 sensors had to be bad maf, $134.00 later, threw it on was not problem, went back next day luckily got my money back, it looked like the remanufactured one was just one they wiped off and put in box for resale! Oh yea, they will read your codes try to sell you parts, but in DE no longer reset your computer, guess Motor Vehicle busted them, people getting reset, running down to DMV for inspection but not fixing problem! Hoping the $100.00 gaskets will fix my headache? Should have kept my 72 Cheynne and 86 Silerado both 350's could work on them!

Tiny
Jackski
Feb 14, 2008.
I may have finally got it! Got intake manifold gaskets from GM dealer for $80.00, four hour job to remove intake and install new ones, truck ran a whole lot better after first start, check engine light had been on for a week, it went off immediately, will know for sure once temp. Outside goes below 30%, will let you know how it goes in a few days. Jackski

Tiny
Jackski
Feb 18, 2008.
To whom it may concern, after all the above trials, it ended up being the intake manifold gaskets! I thought right after installing them it ran 110% better, but now after two or three 25 degree start ups in the morning, no more r.P.M. Problems, rough idle, almost stalling, check engine light, or just running like crap when cold, plastic intake and gaskets who ever thought of that? Rubber gasket material on old gaskets were flattened out, so even if you tried retorqing the intake it just bottomed out on the plastic, Lets see how many miles I get out of this set! Jackski.

Tiny
Jackski
Feb 21, 2008.
Well, looks like you went through hell just to get gaskets! I had a simalar problem, with my 4.3 in my silverado. But mine would run rough all the time, vacum leak, bad hose. I understand what you mean by keeping the old 350's. They are alot easier to work on!

Tiny
Corvette73
Feb 22, 2008.