Engine died while driving/ sometimes no spark

[Rodsridess]

87 Monte SS: In the spring....I had cranking and no spark. It fired all winter in garage no problem! New module, plugs, cap/rotor...all MSD including coil! Got I running...all good! Drove all summer until 3 weeks ago....it heavy miss....not just a plug wire!
The tach was jumping! Got it home without another episode!
Now....the engine died while driving....not totally....just very low RPM sputter/shutter! Turned engine off....restart and it fired right up...put in gear, died again! Turned key... fired up and drove direct home about 15min with no other issue! Checked wiring, coil...not sure what's next to look at

 

[pontiacgp]

I would check the coil first...

 

[fleming442]

Battery cables/connection. Also, verify run voltage 13.8-14.4 VDC

 

[pontiacgp]

I'm not sure what kind of coil you are using but you mentioned the tach was jumping around. I have VDO 5" tach that I installed in the cluster and the tach wire came up as a ground one day. It shorted the MSD remote coil which killed the spark until I removed the tach wire from the coil. You might want to look at the tach wire going to the coil to make sure the tach isn't causing your problem

 

[bracketchev1221]

Since you replaced everything in the distributor, check the magnetic pickup in the distributor. It is a star shaped magnet. I had an HEI in my 78 years ago, and the car ran fine. Swapped over to an MSD box and coil, and the car wouldn't start. Put all the internals back in the distributor and it fired. Took it apart, and changed the trigger and the car fired right up with the MSD.

 

[pontiac guy]

Since you replaced everything in the distributor, check the magnetic pickup in the distributor. It is a star shaped magnet. I had an HEI in my 78 years ago, and the car ran fine. Swapped over to an MSD box and coil, and the car wouldn't start. Put all the internals back in the distributor and it fired. Took it apart, and changed the trigger and the car fired right up with the MSD.

This is the answer. It's the most overlooked part in the distributor. The wires out of the pick up break and make intermittent contact. It gives a no spark sometimes and runs fine others.

Pull the distributor, drive the pin out of the gear pull the shaft out the top. Change it and reassemble. Easy. Sometimes the shaft doesn't want to come out because old nasty has built up in there just work with it. It will come out.