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Rough and uneven idle on cold Morning

Tiny
JACKSKI
  • MEMBER
  • 2002 CHEVROLET SILVERADO
V8 two wheel drive automatic 63,000 miles.

Thought I had bad gas, never did it before just in morning on cold thirty degree nights, morning start ups, engine would start, high idle at 1000 rpm, then idle down to 700 or 600. After about a minute or so it will idle rough, sometimes idle down to 300 to 400 rpm, 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 sometimes but not all the time will do the same rough start up. Have put new vacuum solenoid on and cleaned inside throttle body with cleaner still have problem. Been working on Chevrolet's for thirty five years having problem with this one. Hope I will not have to go to $100.00 per hour GM shop! Could it be throttle sensor or other sensor on throttle body? Jack Ski
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Wednesday, January 30th, 2008 AT 7:05 PM

8 Replies

Tiny
ASIRMANS
  • MEMBER
  • 3 POSTS
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.
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Wednesday, January 30th, 2008 AT 7:17 PM
Tiny
JACKSKI
  • MEMBER
  • 11 POSTS
Warmer weather has set into Delaware the last couple of days, truck starts much smoother now with almost no noticeable rpm pulsating. Did not change throttle body gasket or MAF. Do you think it might be something other than gasket or MAF? Oh, yea what is the K&N you mentioned before? Thanks, Jackski
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Thursday, February 7th, 2008 AT 2:41 PM
Tiny
JACKSKI
  • MEMBER
  • 11 POSTS
Well, her we go again, thirteen degrees this morning, started truck, trucks rpm 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 thirty seconds, rpm's shuttered from 700 to 400 while in gear. Ran rough while in gear at stop, finally after twenty minutes of running idle cleared. What sensor could this be? Jackski
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Monday, February 11th, 2008 AT 1:01 PM
Tiny
JACKSKI
  • MEMBER
  • 11 POSTS
Got this information from a service writer at GM dealer also from owner of local repair shop in business for thirty 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 sense since when warmed up engine 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.
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Thursday, February 14th, 2008 AT 7:38 PM
Tiny
JACKSKI
  • MEMBER
  • 11 POSTS
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 re-manufactured 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 1972 Cheyenne and 1986 Silerado both 350's could work on them.
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Thursday, February 14th, 2008 AT 8:14 PM
Tiny
JACKSKI
  • MEMBER
  • 11 POSTS
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 temperature outside goes below thirty degrees. Will let you know how it goes in a few days. Jackski
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Monday, February 18th, 2008 AT 8:22 PM
Tiny
JACKSKI
  • MEMBER
  • 11 POSTS
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 twenty five degree start ups in the morning, no more rpm problems, rough idle, almost stalling, check engine light, or just running badly 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 re-torqing the intake it just bottomed out on the plastic. Lets see how many miles I get out of this set! Jackski.
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Thursday, February 21st, 2008 AT 1:23 PM
Tiny
CORVETTE73
  • MEMBER
  • 12 POSTS
Well, looks like you went through a lot just to get gaskets! I had a similar problem, with my 4.3 in my Silverado, but mine would run rough all the time, vacuum leak, bad hose. I understand what you mean by keeping the old 350's. They are a lot easier to work on!
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Friday, February 22nd, 2008 AT 11:38 AM

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