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#1 |
Registered User
Join Date: Aug 2010
Location: Ventura
Posts: 151
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Puff/Miss in exhaust.
I noticed recently, my 1990 Suburban 5.7 has a slight puff or miss in the exhaust at idle. Its not consistant, might puff 3 times in a row, stop for a second, puff once then start missing/puffing again. I did a compression test and all cylinders where between 145 to 150 psi. I dont notice a performance difference. I guess its just annoying haha Any ideas? Exhaust leak? Bad plug? Burnt valve?
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#2 |
Registered User
Join Date: Jun 2010
Location: Upland Ca
Posts: 4,144
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Re: Puff/Miss in exhaust.
I would start with an ohms check on the wires, how old are they? Check to see if wire numbers 5 & 7 are touching anywhere. As they run next to each other in the firing order they could be cross firing, this usually happens under light load but could happen at idle. How old are the plugs, cap, rotor?
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1972 C10 SWB, Air, PS, PB, 350/350THM. Second owner. 1965 Corvette roadster, 44K miles, 327/365 SHP, 4 speed, side exhaust, knockoffs, teak, second owner (bought in 1970), Have ALL numbers matching components. My frame off restoration thread: http://67-72chevytrucks.com/vboard/s...d.php?t=556703 |
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#3 |
Active Member
![]() Join Date: Jul 2007
Location: Centrally located between Houston, Austin and Waco. BCS area.
Posts: 7,947
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Re: Puff/Miss in exhaust.
Could be several things, but start with exhaust leaks. That's the easiest thing to check. Look at all hoses carefully. I found a cracked one my BIL had missed by pulling it off and looking at the back side. If all that checks out then ignition parts can cause that including defective spark plug.
As LeeH mentioned check for crossfiring also. I like to do it at night by misting the dist cap and wires with a fine spray from water bottle.
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68 GMC 250/3 speed Saginaw p/b p/s 69 Chevy 350/350 currently in pieces still lookin for a cab 06 Trailblazer I just want a vehicle that I can work on, that won't talk to me, leave error msgs or keep track of how I drive... |
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#4 |
Registered User
Join Date: Aug 2010
Location: Ventura
Posts: 151
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Re: Puff/Miss in exhaust.
Thats for the replys guys. The wires and dizy cap and rotor are new, maybe a month old, but the truck has been doing this long before. The spark plugs themselves I havent checked in awhile, I know they are under a year old though. And I havent heard or seen an exhaust leak, i installed new donuts on the manifolds maybe 2 months ago.
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#5 | |
Active Member
![]() Join Date: Jul 2007
Location: Centrally located between Houston, Austin and Waco. BCS area.
Posts: 7,947
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Re: Puff/Miss in exhaust.
Quote:
Have you also checked for intake leaks? Unfortunately, there's several things that can cause the miss including distributor itself and/or emission parts. If you can have it diagnosed in a shop, that would be the easiest and fastest, otherwise, you just have to start eliminating.
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68 GMC 250/3 speed Saginaw p/b p/s 69 Chevy 350/350 currently in pieces still lookin for a cab 06 Trailblazer I just want a vehicle that I can work on, that won't talk to me, leave error msgs or keep track of how I drive... |
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#6 |
*** That's interesting ***
Join Date: Oct 2008
Location: Pittsburgh, PA
Posts: 2,772
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Re: Puff/Miss in exhaust.
I agree with others. It's a 90, so TBI right? Could it be an injector misfiring?
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Tom ![]() Chevy by day... 1969 Chevy C30 Rollback Tow Truck -- 383 stroker, 4L80E 2011 Chevy Caprice PPV 9C3 6.0L 1995 Chevy Caprice 9C1 1994 Chevy Caprice 9C1 #3 1995 Chevy Caprice Wagon #2 1995 Chevy Impala SS Mopar by night... 1969 Dodge Charger 1972 Chrysler Newport 2dr Hardtop (27K miles) Plus others... |
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#7 |
Registered User
Join Date: Aug 2010
Location: Ventura
Posts: 151
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Re: Puff/Miss in exhaust.
The fuel injectors are new, Ive watched the srpay pattern with a light and the truck running and I dont see any drips. Also has a newer fuel pressure regulator.
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Tags |
exhaust, misfire, miss, puff |
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