Engine misfire

Series I L27 (1992-1994 SE,SLE, SSE) & Series II L36 (1995-1999 SE, SSE, SLE) and common problems for the Series I and II L67 (all supercharged models 92-99) Including Olds 88's, Olds LSS's, Olds 98 91-96, Buick Lesabres and Park Avenue 91-96. Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.
96 SSEi
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Re: Engine misfire

Post by 96 SSEi »

the only sure way is to tear the top end down and inspect the lim/uim and then head
poverty forces one to do unorthodox things

2000 SSEi
past rides:
1996 SSEi
1992 GTP
1987 Grand Am
MKMike
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Re: Engine misfire

Post by MKMike »

You probably have blown out the head gasket, as this can cause oil in the coolant.
In any case, the problem is in the cylinder or cylinder head, not simply the intake.
A blown intake gasket will not lower compression.
The intake gasket does not seal the cylinder---the head gasket, valves and rings do that.
A cylinder leakdown test will tell you where the compression loss is coming from.
https://mobiloil.com/en/article/car-mai ... kdown-test
Potto1991
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Year and Trim: 1999 Pontiac Bonneville SSE

Re: Engine misfire

Post by Potto1991 »

ok so i replaced both intake gasket and head gasket but its still running rough and has a taping noise but it doesn't overheat anymore and no check engine light but it shakes really bad at idle but the tapping sound goes away when u accelerate
96 SSEi
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Joined: Sun Aug 22, 2010 11:11 pm
Year and Trim: 2000 Bonniville SSEi L67
Location: Ontario, Canada

Re: Engine misfire

Post by 96 SSEi »

hi, is the shake there in neutral and drive idle or just drive?
poverty forces one to do unorthodox things

2000 SSEi
past rides:
1996 SSEi
1992 GTP
1987 Grand Am
Potto1991
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Joined: Thu Apr 21, 2016 2:35 pm
Year and Trim: 1999 Pontiac Bonneville SSE

Re: Engine misfire

Post by Potto1991 »

just drive
Potto1991
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Year and Trim: 1999 Pontiac Bonneville SSE

Re: Engine misfire

Post by Potto1991 »

i mean drive idle like when at a stop light or stop sign
96 SSEi
Posts like a Northstar
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Posts: 1813
Joined: Sun Aug 22, 2010 11:11 pm
Year and Trim: 2000 Bonniville SSEi L67
Location: Ontario, Canada

Re: Engine misfire

Post by 96 SSEi »

ok, I had a rough idle and traced it to MAF - unplug it: it is directly ontop of throttle body and has abc on it - see if your issue changes - it will throw a po102 maf circuit low volts.

also, get it to shake and pop the hood and inspect engine mounts - maybe you left one loose or its failing.
poverty forces one to do unorthodox things

2000 SSEi
past rides:
1996 SSEi
1992 GTP
1987 Grand Am
MKMike
Posts like an L67
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Posts: 1305
Joined: Thu May 01, 2014 9:37 pm
Year and Trim: 1993 SLE
1998 SE
2001 SSEI
2002 SSEI

Re: Engine misfire

Post by MKMike »

The rough idle and the noise may or may not be related.
Did it make this noise before the gaskets were replaced?

Are you sure the spark plug wires are going to the correct cylinders?

Are you getting any codes?

Did you change the oil after replacing the gaskets?
It's a must, since oil and coolant had mixed, plus other contaminants can get into the oil when replacing the gaskets.

Unfortunately, it's also possible that something was damaged by the coolant mixing with the oil.

Did you have the head checked for cracks and/or warpage ?

Recheck compression.

Carefully inspect the spark plugs.
You could have one or more bad plugs--cracked, not firing, worn electrode, etc.

Are any spark plugs wet with gasoline or oil?

Double check the spark plug gap.

Did you replace the o rings and gaskets between the supercharger and the lower intake manifold?

Inspect all vacuum hoses to see if any are cracked or loose or disconnected.

Has fuel pressure been checked?

Has the fuel filter been replaced in recent memory?

Harmonic balancer issues are rather common.
Remove the belts and start the car. If the noise goes away, it's usually the harmonic balancer.
If it stays, then your engine has other issues.
Potto1991
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Year and Trim: 1999 Pontiac Bonneville SSE

Re: Engine misfire

Post by Potto1991 »

now i have a broken power steering bolt and i cant get in there to drill it out
bkrkkk871216
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Year and Trim: 2001 pontiac boneville ssei supercharged

Re: Engine misfire

Post by bkrkkk871216 »

Ok I know i have a head gasket out and but I have used blue devil like crazy and failed the instructions then over heats again and then it feels like the compression is going to my antifreeze. You guys have any suggestions about taking a spark plug out and then running it or something like that. I dont know which cylinder or anything yet
bkrkkk871216
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Re: Engine misfire

Post by bkrkkk871216 »

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J Wikoff
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Re: Engine misfire

Post by J Wikoff »

How do you know you have a bad headgasket? The LIM gaskets are far more likely to fail and have similar symptoms. What is "blue devil"?
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