silveradobo454
Forum Newbie
Posts: 28
Age: 37
Loc: Jacksonville, Fl
Reg: 04-06-12
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 04-30-12 08:15 AM - Post#2220624
My 1990 gmc suburban, 350 tbi 4wd had a nasty miss on cold mornings. If its less than 70 outside and I'm starting up to go to work, if I don't let the motor warm up for a good five to ten mins, when I hit the gas and the rpms go up I feel it hit and miss when under load. Once warmed up all ie good. Idles fine. Starts up fine. I have checked and or replaced the following.
Tps
Iac
Est
Esc
Plugs
Wires
Coil
Fuses
Distributer
Ecm replaced x 3
Prom replaced x 2
Ecm wiring harness
Head gaskets
Grounds
Egr
All vacuum lines replaced and checked.
Egr solenoid
Coolant temp sensor
Alternator
Battery......
What have I missed and what in the world is going on.
| If I had a dollar for every wrench I've turned, Bill Gates would be my butler. |
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chevyracing58
Contributor
Posts: 437
Age: 21
Reg: 01-29-10
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04-30-12 07:45 PM - Post#2220911
In response to silveradobo454
Check timing you could be one tooth off
1998 chevy silverado 350 bored to 383 spec 6" lift 33" swampers completely blacked out
04 chevy tahoe 5.3
1989 k1500 350 sold
1988 k1500 350 sold
1989 chevy s10 4.3 sold |
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 CowboyTrukr
"2nd Year" Silver Supporting Member
Posts: 705
Loc: Salt Lake City
Reg: 06-20-09
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04-30-12 09:19 PM - Post#2220942
In response to silveradobo454
Bo, it's sounding like symptoms of problems with the ignition control module. What exactly did you do with the distributor?
Greg
'94 Silverado K2500 4X4 5.7 5spd Xcab LB
RV cam, Pace Setter Headers, TBI spacer, Flow Tech air cleaner adapter, Hypertech street chip
"The only thing necessary for evil to triumph is for good men to do nothing" Sir Edmund Burke |
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navygunner08
Silver Supporting Member
Posts: 613
Loc: New London, CT
Reg: 02-13-11
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04-30-12 11:35 PM - Post#2220979
In response to CowboyTrukr
Which temperature sender did you replace... the one next to the thermostat or the one in the head?
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silveradobo454
Forum Newbie
Posts: 28
Age: 37
Loc: Jacksonville, Fl
Reg: 04-06-12
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05-01-12 06:28 AM - Post#2221046
In response to navygunner08
One by one answers. The timing has been checked multiple times and set as per the VECI label under hood for this motor. I have also tried a retard and an advanced up to 9 deg and no difference was made so I put it back to factory spec.
The distributer was replaced the first time with a reman unit. Then a second time with a Cardone Select new part. No difference made.
As for the coolant temp sensor. The cts on the manifold is the only one in the book. There is a discrepancy between the transmission controled spark sensor and just the plane temp sensor showing you the block temp in the cab that is located on the drivers swore head. The sensor on the driver side head only has one wire on it and when unplugged the only thing it does is make my temp guage tread zero.
| If I had a dollar for every wrench I've turned, Bill Gates would be my butler. |
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silveradobo454
Forum Newbie
Posts: 28
Age: 37
Loc: Jacksonville, Fl
Reg: 04-06-12
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05-01-12 06:39 AM - Post#2221054
In response to silveradobo454
I will also add a few things I didn't mention to the done list.
The fuel system has been completely overhauled. Including
Fuel lines
Fuel filter
Fuel pump filter strainer
Pump
Pressure regulator
tbi unit has been cleaned and flowbench tested with a rebuild kit installed, new injectors
All lines, fittings, and gaskets are new from the filler neck to the tbi unit.
Fuel tank has been cleaned out and free of all debris.
Fuel pressure steady at 13 psi wichyas to my knowledge factory tbi trucks were set between 12-15 psi stock. So I'm good with the fuel system. All of which again has made no difference.
| If I had a dollar for every wrench I've turned, Bill Gates would be my butler. |
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elcamino
Valued Contributor
Posts: 4812
Loc: Lake Superior-Michigan US...
Reg: 03-30-00
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05-01-12 01:13 PM - Post#2221183
In response to silveradobo454
I had a '92 Silverado that ran terrible when first started. Had to let it warm up or it would die trying to drive away even when warm out. It would stmble and miss. Like you I replaced the plugs, wires etc. Finally got fed up and took to the Chevy dealer and they found the 02 sensor was bad. They replaced it and it ran perfectly from them on. It was original woth 80,000 miles..
Mike
2009 Cadillac CTS4 AWD Performance Sedan
2012 GMC Sierra AWD Denali 6.2L |
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silveradobo454
Forum Newbie
Posts: 28
Age: 37
Loc: Jacksonville, Fl
Reg: 04-06-12
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05-01-12 02:00 PM - Post#2221203
In response to elcamino
I thought the same thing at one point in time. But it didn't make sense because the o2 sensor does nothing until it get @ 600 degrees then the ecm goes into closed loop. So I changed it anyways and once again no difference.
| If I had a dollar for every wrench I've turned, Bill Gates would be my butler. |
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silveradobo454
Forum Newbie
Posts: 28
Age: 37
Loc: Jacksonville, Fl
Reg: 04-06-12
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05-29-12 11:27 AM - Post#2231158
In response to silveradobo454
Well now its almost summertime and the truck won't do the hit and miss. Once it gets cold again I'm sure it will come back and when it does I hope I can find the problem. If anyone finds out or thinks of anything in the mean time please suggest anything.
| If I had a dollar for every wrench I've turned, Bill Gates would be my butler. |
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silveradobo454
Forum Newbie
Posts: 28
Age: 37
Loc: Jacksonville, Fl
Reg: 04-06-12
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07-17-12 11:51 AM - Post#2249122
In response to silveradobo454
The problem has been resolved. Finally I found out what was going on. Not too long ago I had to replace the starter. When I removed it a small piece of header gasket shaped like a T fell on me. After pondering for a bit I discovered were it came from. It was the small section of gasket that is in the middle of the header for the two exaust ports that are close together on the SBC heads. The middle and bottom of it had gotten hard and broke off. I didn't think anything of the header gaskets because when I bought new headers last year they came with new gaskets, and cheap ones they were. I replaced both sides with new Fel-pro gaskets and to my supprise about a month ago it got cold enough around here to see my breath, and one morning it wad about 57 and the truck never rid the hit and miss anymore. Dam I am glad that's over with.
| If I had a dollar for every wrench I've turned, Bill Gates would be my butler. |
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