[Doug Flynn]

I finally got my car back together. It was apart for 1 and a half years. I redid a lot of the wiring and rebuilt the motor. The problem is that the engine has a severe miss (breaks up very badly, all cylinders) between about 2300-2900 rpm. It is definately ignition related I feel. The tach need goes crazy when this happens. Below 2300 it is fine and when the engine hits 3000 rpm the problem completely disappears and runs fine. The engine is a sbc with HEI distributor (81+ model without mechanical advance, the engine has an aftermarket efi system which controls timing). The timing is set ok, the rotor is indexed ok. I did take the ignition module in the distributor to the auto parts store and they checked it and said it is ok. I don't know if their test could catch this problem.

I did accidentally hook the power wire for the distributor to the tach output and put 12v to it. I wouldn't think that would damage the magnetic pickup.

Could this be the module or the mag. pickup.

Any help is truly appreciated.

 

[JWagner]

Just to be sure, put your timing light on it and drive it into the misfire situation with the timing light in operation. Also, check the continuity of the pickup coil as these do not last forever and are cheap ($15-$25) to replace.Check all connections and make sure that it really is getting 12volts all of the time.

 

[RBOMAR]

I have been plauged with the same problem for about a month now. I get a small but detectable miss at 2000 - 2250 rpm under normal driving conditions. When I first noticed it, I found 2 oil fouled plugs. Replaced them but the miss did not go away. Next replaced the cap, rotor and wires. Still had the miss. I have also checked for vacuum leaks and did a compression test on all cyls and got from 150-155 on all. I am stumped! What else should I check or replace? Module, coil, mag pick-up? ?

 

[Doug Flynn]

Popped in a new module and problem solved. By the way, like I mentioned, I had an auto parts store test it and they said it was ok. Obviously not a comprehensive test.
Bad modules Cause a lot of different problems.

 

[GregGillette]

Pickup coil can cause this too. Wires flex as advance occurs and the copper strands within wire will make and break at different RPMs.