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spark plug stops firing (when cold)

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Old 12-22-2003, 09:27 AM
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spark plug stops firing (when cold)

Lets see, relivant info...

Just got new heads and carb
holly 4777C (650 double pumper)
protopline iron lightning 2.02 /1.60, 180cc 64cc
compressions is about 9.5:1
cam .493/.500 218/224 @.50

new plugs (accell header plugs) gapped 0.045
new 8mm wires (nothing special.. autolite i think)

OK, after i got the new heads and carb put on engine ran fine for a few days. Now 2 mornings in a row car starts, idles fine and when i go to drive one plug stops firing. If i put it in neutral and rev to 4500-5000 the plugs starts firing again.

It is the same plug everytime, I can tell by how it runs, but I havent checked to see which plug it is yet.

So the plug isnt actually fouled, just wet.
Once the car is warmed up it will be fine for the rest of the day, even if it cools down again.

Some things I was thinking might help.
larger or smaller gap - im assuming larger
new distributor cap- 2 of the terminals were chalky when i changed the wires.
new coil - its about 3 years old
richer or leaner mixture - im assuming richer (very slightly richer since its running perfectly besides this)

any ideas?
Old 12-24-2003, 07:38 AM
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-bump- cause this is driving me crazy
Old 12-24-2003, 08:09 AM
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ede
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how do you know one plug stops firing? since you don't know which one stops and you're pretty sure it is a plug that stops firing why not just change them all and you should have your problem fixed.
Old 12-24-2003, 10:48 AM
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The plugs that are in the car are 2 weeks old.

I know its the plug because the last time this happened i changed the plugs and one of them was wet with gas, all the rest were fine.

It feels exactly like it did before i changed the plugs, so I am assuming the same thing is happening.

I am going to change the cap, rotor and HEI coil, hopefully that will fix it. Maybe my current setup isnt hot enough to get a spark... that would be a little strange, but a few of the terminals on the cap were a little chalky when i changed the wires over the weekend.
Old 12-24-2003, 12:14 PM
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Car: 82 z28
Engine: 355
Transmission: 350
I had a simalar thing happening last summer. A week or so after doing a complete tune up,( cap rotor wires and plugs) Drove me crazy cause I ran outa' places to look for trouble. I also tried changeing the coil for an extra one with no luck. But with my car after start up different plugs would'nt fire right. 1 or 2 plugs would stay cold and other times they'd just warm up, I could still hold my hand on those pipes with the car running. After I switched every plug for new ones the problem totally went away. I never thought new plugs could mess up like that but sure enough. In my case I was useing ac delcos r45ts gapped at .40 . I still am, with the same gap . When I went up to .50 it ran good up until higher rpm driveing, then it would start to miss. Are you useing the plugs pro topline recomends with those heads?

Last edited by cz350Z; 12-24-2003 at 12:58 PM.
Old 12-24-2003, 01:44 PM
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I am running the only plugs that will fit with my headers =\

Accel shorties, i cant remmeber the part number for my life
Old 12-24-2003, 02:24 PM
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ede
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doesn't really sound like a problem with your plugs but more like a dead wire to me. might be a cap or rotor problem but i'll bet on the dead wire.
Old 12-24-2003, 06:26 PM
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hehe wires are brand new too
Old 12-24-2003, 06:51 PM
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Car: 82 z28
Engine: 355
Transmission: 350
I left out the module cause they usually act up after the engine heats. If it was my car I'd try dropping another distributor in it to make sure the pick up coil is ok,or have it put on a bench and tested. I assumed the wires were new. Sometimes cheap wires arc, or they might not be getting proper contact to accept the juice if you crimped em' yourself and botched 1. I'd consider everthing.

Last edited by cz350Z; 12-24-2003 at 07:10 PM.
Old 12-29-2003, 10:59 AM
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Ok, pretty much the entire ignition system is new now.

plugs
wires
cap
rotor
coil
iginition module

It seems that if i let the car warm up to about 190-200 the problem doesnt occur, only thing is, it takes about 15-20 minutes to do that... so I am wondering if there is a way to "fix it" or if its not really a problem and I am just going to have to let the car really warm up before i put it in gear.
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