Misfire on #6
Thread Starter
3rd Gear
Joined: Sep 2013
Posts: 3
Likes: 0
Misfire on #6
Totally lost! 1985 - suddenly just quit. Hard start then just would not stay running. Buddy checked and fuel pressure was dropping. Maybe fuel pump?-replaced. Still would not run. Finally gave up and took to garage. Hose to PVC replaced, will now start and run but mis-firing on #6. Replaced fuel injector on #6. Runs ALOT better but still missing on #6. Replaced all 8 injectors. Checked cam for flat spots, lifters checked, checked for carbon build up. Excellent compression,no wet or fouled plugs and everything checks out but still misses on #6 when running 35 MPH or less. When idling will sometimes miss and sometimes not. Runs like a dream over 35. Not sure if distributor was checked?? Very reputable mechanic is totally stumped to the point of all labor has been written off and only paying for parts. ANY IDEAS? I am losing my mind.
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
Totally lost! 1985 - suddenly just quit. Hard start then just would not stay running. Buddy checked and fuel pressure was dropping. Maybe fuel pump?-replaced. Still would not run. Finally gave up and took to garage. Hose to PVC replaced, will now start and run but mis-firing on #6. Replaced fuel injector on #6. Runs ALOT better but still missing on #6. Replaced all 8 injectors. Checked cam for flat spots, lifters checked, checked for carbon build up. Excellent compression,no wet or fouled plugs and everything checks out but still misses on #6 when running 35 MPH or less. When idling will sometimes miss and sometimes not. Runs like a dream over 35. Not sure if distributor was checked?? Very reputable mechanic is totally stumped to the point of all labor has been written off and only paying for parts. ANY IDEAS? I am losing my mind.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
I had a miss on #6. I found it by looking at the spark plug wires in a dark garage. It was arcing to the oil dipstick tube. When I pulled the plug boot off the plug it fell off the spark plug wire. The inner conductor was burned away by the arc inside the wire. When the gap inside the wire got big enough it was easier for the spark to go to the dipstick tube ("the path of least resistance" in action).
Thread Starter
3rd Gear
Joined: Sep 2013
Posts: 3
Likes: 0
Thanks for all the suggestions! Will check to see if plug wire/wires have been replaced. I know plugs are all dry with no cracked conductors. I assumed that when he checked plugs for damage, moisture and gap, he checked wires and distributor. But you know what assuming will get you. Will ask specifically if that has been done.
