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Changed Spark Plugs 79 Camaro Now Misfires??
11-19-2008, 09:41 PM
I recently changed the spark plugs out on my 1979 Camaro which has a small block 350 bored at .30. The engine ran great and there was no problem prior to this. I replaced the old Champion RV12C's with some new ACDelco R45TS plugs and gapped them at .045 in. and it seemed to run fine at idle, but going through the gears on the road I notice a pretty consistent vibration/misfire. It seemed like just 1 cylinder wasn't firing. After inspecting the distributer wires I noticed one was frayed so I completely replaced it, along with verifying all the plugs/caps were seated properly and corrosion free. I also checked for anything that might have been out of place like hoses, wires...everything seems to be in order?
So does anyone have any ideas what could have happened? I mean it feels like the timing is off or something but the only thing that changed was the plugs.
11-19-2008, 10:30 PM
That usually is the sign of a misplaced plug wire. If you double check the wires and they turn out to be in the correct order the only other thing you can check is the new plugs you put in.
11-20-2008, 09:53 AM
I pulled them out last night and they seemed fine, now it could be a possibility that I have a set of wires on the wrong plugs, I will try switching them around and see what happens? Any other possibilities?
11-20-2008, 11:58 AM
I'd be looking for a incorrect firing order as you are. Also, make sure you didn't route a wire too close to the exhaust and burned one thruogh or a wire not fully seated. Double check your plug gap and look for any cracks in the porcelin insulation of the plugs.
11-20-2008, 07:31 PM
One thing I did find is that with the new 8mm wire that I just replaced is seated so close to the exhaust that it melted away some of the rubber boot! within 1 day! There is no metal exposed but other than needing to wrap my headers in some kind of insulation I really cant see a slightly melted boot being the problem. I did buy an ignition testing gauge (the one you hook up to the end of the wire to test for spark) but haven't tried that yet. But thinking logically about the things I changed, there shouldn't be too many things that could have gone wrong, I.E.
1. Engine Runs smooth
2. Change spark plugs from Champion to ACDelco gapped at .045
3. Engine slightly loping/misfiring at idle (barely noticeable)
4. Engine loping 90% throughout acceleration (noticeable)
5. Completely replaced melted distributor wire on cylinder 5
6. Nothing changed, hit the forums
Would it be impracticable to replace the whole set, or go through one by one with a new plug?
Thanks for all the help, crazy ass problem
11-21-2008, 10:16 AM
It takes not even the tiniest one-thoussandths of a inch hole for the spark to 'leak' out. Remember, electricity is like water and takes the shortest path of resistance. It definately sounds to be your problem.
11-21-2008, 11:31 AM
you can buy heat shields for the plug wire boots. They sell them at www.summitracing.com or jegs
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