Misfiring

Tiny
ROBERT_45
  • MEMBER
  • 1970 CHEVROLET CHEVELLE
  • 4.1L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 50,000 MILES
Got our car started today and to no surprise it began misfiring. As you can see in the video it misfired terribly at a low idle and high idle but it's not consistent. We started it up three times and each time it stalled after a few minutes of off and on misfire. We start the car every year and about 2 or 3 years ago we had it running pretty well. It began misfiring one day and we could never figure out why. It's got many new parts in it since we tried several things to solve this problem. We replaced the points and condensers, fuel filter, ignition switch, distributor cap, fuel pump, the air cleaner, and spark plugs with wires. We've narrowed it down to possibly putting the ignition switch in wrong, carburetor, voltage regulator, or maybe even the whole distributor. Whenever we put new points in the vehicle they get burnt fairly quickly at an idle. We're not for certain these could be the problems so if anyone has some knowledge on the topic please let us know. The car is listed above with inline 6 cylinder 250 engine.
Saturday, July 20th, 2019 AT 3:00 PM

1 Reply

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good afternoon,

Good video, thanks.

Some things to check.

1. Look for vacuum leaks at the intake manifold to the head.

2. Carburetor with the age, I would rebuild it as it may have dirt inside clogging air bleeds.

3. How old is the fuel? Fuel older than a year is no good.

4. Do a compression test as well to be sure the valves are not hanging up in the guides from carbon build-up.

Roy
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Saturday, July 20th, 2019 AT 3:36 PM

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