Still Missing
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True Car Nut
Joined: Jan 2004
Posts: 4,328
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From: Lakeville, MN

Well, I just got rid of the Bosch plugs and put in AC Delcos and still have a miss under load. :? They are factory gapped to 0.60 so I didn't bother checking. Do you think there is a possibility they might not have gapped them propery?
Have you scanned for codes yet? That could tell you exactly what is causing it.
I was told the NGK were pre-gapped for .060" and the first time I put them in my 1994 it was only running on 3 cylinders. Pulled the plugs out and found them all down around .035" -.040". That was almost 1.5 years ago, and now the 4th time I've put NGK'* in Ol Blue I checked the gapping and found the same factory gapping to be .035"-.040". Way off and causing heavy missfiring. I'd suggest pulling them and verifying the proper gapping. If they aren't correctly gapped you can pick up a cheap plug gapper for like $0.99 at Wal-Mart or Fleet Farm, etc...
I was told the NGK were pre-gapped for .060" and the first time I put them in my 1994 it was only running on 3 cylinders. Pulled the plugs out and found them all down around .035" -.040". That was almost 1.5 years ago, and now the 4th time I've put NGK'* in Ol Blue I checked the gapping and found the same factory gapping to be .035"-.040". Way off and causing heavy missfiring. I'd suggest pulling them and verifying the proper gapping. If they aren't correctly gapped you can pick up a cheap plug gapper for like $0.99 at Wal-Mart or Fleet Farm, etc...
Just my opinion but I would go in this order until the problem is solved:
1) Check old plugs for carbon tracking, particularly cylinders 2 and 4:

If you find it on a plug then replace the corresponding wire because it is toast. According to GM this is a particular problem on 93-93 L27 and L67 engines. I don't know why.
2) If you have a multimeter, check the resistance of the wires. Make sure they all conduct electricity.
3) Check the gap on your spark plugs just in case they were knocked in the shipping process.
4) Replace all the wires.
5) Check the resistance on the ignition coils.
6) Excessive alternator output? Now I'm running out of ideas.
My money says wires. I've had bad wires twice.
1) Check old plugs for carbon tracking, particularly cylinders 2 and 4:
If you find it on a plug then replace the corresponding wire because it is toast. According to GM this is a particular problem on 93-93 L27 and L67 engines. I don't know why.
2) If you have a multimeter, check the resistance of the wires. Make sure they all conduct electricity.
3) Check the gap on your spark plugs just in case they were knocked in the shipping process.
4) Replace all the wires.
5) Check the resistance on the ignition coils.
6) Excessive alternator output? Now I'm running out of ideas.
My money says wires. I've had bad wires twice.
I'd have to agree:
Check plugs (excessively quick wearing)
wires (for continuity)
coils
wires feeding up to coil pack plate
I've had problems with a coil pack on another car so if your plugs and ires are fine that would be my best bet.
KK
Check plugs (excessively quick wearing)
wires (for continuity)
coils
wires feeding up to coil pack plate
I've had problems with a coil pack on another car so if your plugs and ires are fine that would be my best bet.
KK
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sp4149
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Apr 26, 2008 07:46 PM



