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Old 12-21-2019, 03:24 PM   #1
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Join Date: Apr 2012
Location: Texas
Posts: 102
Backfire through tbi

Hi all,

I'm having trouble with my 90 burn tbi. Engine is 1 year old.

Runs fine when I first start it, but as she warms up she starts to backfire through the tbi. Especially on the highway.

I've replaced the plug wires, plugs, cap and rotor. Checked the ignition control module, it was fine but I replaced it and have the old one as a backup. I also set the timing.

Any ideas would be greatly appreciated
1990 suburban r1500 k 350 2wd
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Old 12-22-2019, 04:29 AM   #2
Greasey Harley
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Join Date: May 2013
Location: Post Falls, ID
Posts: 673
Re: Backfire through tbi

Did this start when you installed the motor, or is it a recent development?
Flat tappet or roller cam?
Tripple checked firing order?
How many miles since rebuild? (Could be a flat cam lobe)

What distributor and ignition system are you using?
What is your timing? Preferably base and total.
Checked for vacuum leaks?

I think you said, you are working on a 90 suburban???? Typo??
Not sure where the cut off is, but I know early to mid 90's gm Halifax dizzys would pop and backfire when the ignition module would start to go out.

Just spitballin'
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Old 12-22-2019, 12:12 PM   #3
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Join Date: May 2015
Location: Montana
Posts: 2,558
Re: Backfire through tbi

Head gasket blown between two cylinders ????
Current/past Chevy/GMC trucks:
1958 Chevy C-60; 1965 GMC C-50; 1965 Chevy C-10
1971 Chevy K-10; 1973 Chevy K-20; 1976 GMC C-20
1977 Chevy C-10 Suburban; 1980 Chevy K-10
1989 Chevy K1500; 1991 GMC V1500 Suburban
2016 Chevy K2500 HD
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