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racer21
New User
Dec 27, 2009, 11:24 AM
Post #1 of 12
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i have a 2002 chevy tahoe 4.8 when i first start it up in the morning it spits and sputers bad almost to the point of dieing when its warm out side its fine but during the winter it is awful have already replaced the tempetur coolant sensor did help any advise thanks
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Sidom
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Dec 27, 2009, 12:13 PM
Post #2 of 12
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Re: 2002 chevy tahoe
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On this one the 1st thing I would do is take a fuel pressure reading and also with the key off make sure the pressure is holding & not bleeding off and then go from there depending on the results........
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racer21
New User
Dec 27, 2009, 12:24 PM
Post #3 of 12
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Re: 2002 chevy tahoe
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buddy of mine done checked that for me its fine once it gets to about 140 engine temp it runs fine the rest of the day just first time i start it each day unles the temp out side is above 60
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Sidom
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Dec 27, 2009, 12:49 PM
Post #4 of 12
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Re: 2002 chevy tahoe
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The quickest and easiest thing would be to talk a look at the datastream when it's cold and see what the temp reading of the coolant temp & air temp sensors are. That could also have an affect on cold/warm starting. There are resistance charts you can use to ohm the sensors but I don't like going that route just due to fact it doesn't tell what the computer is reading.
You could try disconnecting the sensors when it's stone cold out, this will max the values to -44 ยบ. If it's real cold out then it should start but would start to run poorly very quickly as it warmed up..
Do you remember what the fuel pressure reading were and how long it held after the key was turned off?
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racer21
New User
Dec 27, 2009, 1:13 PM
Post #5 of 12
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Re: 2002 chevy tahoe
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no dont remeber what they were sorry and yea mine starts and runs very poorly till the motor warms up and then its fine rest of the day ive had it to the dealer and every where no one has a clue they all told me it was the coolant temp sensor so i replaced it this morning did change a thing so now im real at a lost for the fix
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Sidom
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Dec 27, 2009, 2:17 PM
Post #6 of 12
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Re: 2002 chevy tahoe
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I usually like going with the basics and start from scratch on problems like this..... Seems like everytime I go with another tech test results (which are usually done correctly) , I wind up spinning my wheels and losing time...
From what you posted it really doesn't sound like a fuel problem (at least not the pump) but it only takes a minute to hook up a gauge. I would pull codes to see if I can get any direction there. Cold I would look at a data stream to make sure all temps jived with ambient temp. If nothing came out from there try to see what area is giving me trouble. Is this a fuel problem? Too rich? Black smoke out the back? Too lean? Propane enriching smoothes it out? Ign problem? Misfire codes or weak spark? Do I have a good battery? How does it load test cold?
Hopefully you could get something from a few of these tests to point you in the right direction
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racer21
New User
Dec 27, 2009, 2:59 PM
Post #7 of 12
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Re: 2002 chevy tahoe
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when u first start it cold it blows black smoke til it warms up it has turned my body above the exast black
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Sidom
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Dec 27, 2009, 3:13 PM
Post #8 of 12
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Re: 2002 chevy tahoe
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Ok that would be a sign of running too rich.
At that point I would want to see the scan data I mentioned to see what is going on with some sensor inputs at the time it's running poorly to get some direction as to what area could be giving some false data
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jstuhl
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Dec 27, 2009, 5:39 PM
Post #9 of 12
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Re: 2002 chevy tahoe
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check the vac. advance first. chevy's are known for this.
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Sidom
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Dec 27, 2009, 7:19 PM
Post #10 of 12
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Re: 2002 chevy tahoe
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Vacuum advances haven't been use for over 20 years...... But did have their problems back in the day....
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re-tired
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Dec 27, 2009, 7:51 PM
Post #11 of 12
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Re: 2002 chevy tahoe
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Would'nt hurt to give the points a few strokes with a points file , test condenser & set dwell . And everybody forgets to put a dab of lube on the distributer cam . Maybe put a set of red advance springs to recurve the mechanical advance. After checking the vac advance mechanism better test the choke-pulloff and 4 barrel lockout . Gawd , those were the days. 
LIFE'S SHORT GO FISH
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