Misfire under boost - Page 3 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1992-1999 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 and Buick Lesabres Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 12-19-2005, 03:48 PM   #21
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Probably time for some fresh wires.
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Old 12-20-2005, 04:50 AM   #22
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I have fixed many of the same problems buy simply changing the plugs and wires. Gap the plugs at .040 and use a NGKs. You will never have another problem!! If you live in a warmer climate, I suggest you go one heat range cooler....it does wonders...and keeps the motor safe from detonation too!!
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Old 12-20-2005, 11:25 AM   #23
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how would reducing the gapping effect my fuel efficiency?
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Old 12-20-2005, 01:56 PM   #24
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Quote:
Originally Posted by *ratedx*
I have fixed many of the same problems buy simply changing the plugs and wires. Gap the plugs at .040 and use a NGKs. You will never have another problem!! If you live in a warmer climate, I suggest you go one heat range cooler....it does wonders...and keeps the motor safe from detonation too!!
On a bone-stock SSEi, .040" is WAY too narrow. That'* going to cause fouling, poor compustion, and in time will destroy your catalytic converter. Not to mention poorer fuel mileage.

Stock gaps of .060 on plugs for a stock (no smaller pulley) SSEi have been proven over and over here. Don't go ANY smaller than a .055" gap on one-heatrange colder plugs IF you live in a hot climate.
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Old 12-20-2005, 09:36 PM   #25
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it wasnt the plugs or wires, i would bet anything that its a vaccum leak but i cant for the life of me find it, ive tracked every line i could see, does anyone have a diagram or something that illustrates all the vaccum lines? also a question, when under boost, would the vaccumlines become pressurized? because i just considered tha and i do know that there is one vacucm line just kinda sits on it'* coupling but easily slide off, it would hold itself undervaccum but if there was pressur ein the line it would come out there
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Old 12-20-2005, 09:40 PM   #26
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im about ready to bust out the electrical tape and seal over every vaccum lin on the car just to be sure
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Old 12-20-2005, 11:32 PM   #27
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Nerv, do the carb cleaner trick. Gently spray it on each connection including around the base of the UIM and LIM. Little controlled squirts. When your idle changes, you found the leak. Look at the fittings under the vac accumulator too. Between the maxifuse relay center and the ws wiper motor.

However, if you're logging misfires on the same cylinder, it'* not a vacuum leak.
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Old 12-20-2005, 11:59 PM   #28
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dont you need to clear one code before you can view the next? i maybe getting misfires under multiple cyls but both times ive pulled codes it was cyl 3, and i rly wanna say its a vaccum leak, the boost guage is moving funny and it includes a general weakness, not the stuttering that i was getting when i single cyle misfiring once
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Old 12-21-2005, 12:01 PM   #29
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The only way a vac leak could affect you like that on an L67 is if the leak was at the LIM front bank center and affected the port for the #3 cylinder only. Pulling in more air (atmosphere) at that port would cause a lean condition if that were the case.

Pull that #3 plug and let'* have a closeup look at it.
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Old 12-21-2005, 12:34 PM   #30
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its a brand new plug, i suspected plugs first thing and replaced emeven tho the old ones all looked good, its brand new plugs and wires
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