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| GMC Suburban Forum Forum for discussions regarding the GMC Suburban |
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#1
02-19-2012, 09:24 AM
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Engine missing on cold mornings
I have a 1990 GMC Suburban 1/2 ton 350 tbi auto trans, V1500 on the vin. It just started giving me misses when I leave for work on the cold mornings this winter. It starts up fine, idles fine and I can rev up in park with no issues. After I put it into gear to go down the road if I hit the gas it misses bad. Sometimes sounds like multiple cylinders, sometimes sounds like one. I have noticed it will only do it when its less than 45 degrees outside in the morning. Will not do it on mornings that are like 50 deg and up. After sitting at work for 10 hours, it will not do it before I go home. After less than 3 minutes of run time it will not do it buy the time I hit the first turn off the highway thats only a half mile from home. After that small time frame it runs like a champ. It doesnt last long but first thing in the morning this pisses me off because it makes my nice duel exhaust sound like a sick dirt bike. I have checked and/or replaced the following,
Tps IAC Injectors Fuel pressure reg Vacummme system all hoses Fuel lines Fuel pump Plugs Wires Distributer Cap Rotor ECM PROM Fuses Wires Please don't say o2 senser, Its been replaced and even if it wasen't it doesent become active untill closed loop @ 900oF so it doesn't count. I have had every body say thats the problem. So guys with all I've done is there anyone that can help and tell me what I've missed. 
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#2
02-19-2012, 11:04 PM
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sounds like a coil... test it when it cold with a volt/oms meter. goggle specs for your year/model
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#3
02-22-2012, 11:32 AM
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did you check your timing?
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#4
02-22-2012, 09:27 PM
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how will the timing only be a problem under 45 degrees?
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#5
02-23-2012, 09:48 AM
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check the battery first an than the alternator. If the battery is getting low on juce you can have the same problem. Alternator as well. If the alternator dosn't gives enough juice te battery is getting low as well.
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#6
03-30-2012, 10:36 PM
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Ok. Now its getting worse. its spring time and now its doing it on mornings that are like 60 degrees out now. Coil is good and alternator voltage is good as long with battery draw and charge. Whats next fellas because its doing it now almost every morning.
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#7
04-01-2012, 07:58 PM
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well i would drop it off at a good repair shop/garage. Let them diag it for you. I know if i had it in front of me i would not need much time to find it if it's as bad as you say.
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#8
04-01-2012, 10:59 PM
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Well you sound like you're pretty confident in finding the issue. Problem is I've had it to an ASE certified shop and they had it for a week and ran it on a vac test, compression test and an ocilligraph and they couldn't figure it out. I myself am ASE cert and can't figure out this ghost in the machine. What have I overlooked.
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#9
04-02-2012, 10:31 PM
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well i can tell you this .. This is what i do best ASE master and GM master tech.
I belive your over looking something that you alrerady did or checked. Not uncomon to have a bad part. Now what i want to know is Does it have black smoke when this happens? Have you check the data stream and looked at the temp sensor reading to see if it's correct? Have you done a top engine cleaning pos valves sticking when cold. (happens) You could hook up a nerd light to go in side of the cab to test injector pulse (done with jumper wires) so you know if they are or not pulsing when it happens. Same with spark tester. Also does your tk have the est box that bolts on the right side of the intake manifold. Answer these questions and i will [post again with more questions.
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#10
04-04-2012, 11:24 AM
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Thank you. I have the truck in a shop getting some paint work done to it and welding work. Once i get it back i will go through these suggestions one by one. As for the est, its on the passenger side of the manifold bolted to the same plate as the egr solenoid and the map sensor. And no the engine does not put out black smoke when it does the hit and miss. I have checked the push rods for deflection, set and checked all rockers and lock nuts to ensure I don't have a top end issue. The valves were checked when I sent the heads off for xray and to have them checked after i had a thermostat issue that caused a little overheating but no known damage to the block or heads. Head gaskets and manifold gasket are new.
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