johnsopa

My '90 C2 all of a sudden started bucking and stalling tonight on the way to dinner. Limped home, fortunately only 10 mins of major bucking, etc.

Can't restart the car -- cranks and somewhat fires but won't maintain idle.

Unplugged the left coil ignition module and the car starts/idles fine, might be a bit sluggish when revving.

Reconnected the left coil ignition module and unplugged the right module. Car won't start again.

Reconnect the right (so now both ignition modules are connected) and the car won't start again.

Unplug left ignition module again to verify and she starts fine.

This means that left coil, ignition module and/or lead are bad, correct?

What I don't get is that if one of those are bad, shouldn't the car still run with them connected since it runs without them connected?

540964

Broken belt in the distributor?

spartansix

You can pull the lower distributor cap and see if the rotor spins freely. If the belt is broken, don't run the car with the lower distributor firing!

johnsopa

A bit puzzling. Both coils are good. Both coil to distributor leads are fine.

Any combination of coils/leads connected to the lower/secondary distributor will run the car fine as long as nothing is connected to the upper/primary distributor cap. Double checked when I took the caps off, neither rotor spins free, so the belt is fine.

Both caps/rotor look good, they basically look new inside.

All of the plug wires on the bottom of the engine (the ones coming from the primary distributor) as well as the wires plugged into the caps are seated nice and tight.

I didn't swap the caps/rotors yet since I didn't want to remove all of the plug wires.

I guess this means the primary distributor cap and/or rotor is bad.

Agree with this?

johnsopa

Just checked my receipts from a year ago (February 2019) -- I installed new caps, rotors, wires and plugs when I dropped my engine to install a LWF. Everything was purchased new from Steve W. at Rennsport.

Silvertarga

time to do the 993 coil swap

johnsopa

I was thinking of doing that but I'm pretty sure now it's not the issue. Either coil connected to the secondary distributor runs the car as long as the other coil connected to the primary has its ignition module disconnected. Swapped the leads too, the problem stays with the primary distributor.

newsboy

How do you know the coils are O.K.? Even coils that test correctly, can have internal faults. Trying new coils is not too expensive.

johnsopa

Hmm. Pretty sure they're both fine. The car runs with the secondary dist cap connected to either coil, using either of the leads, as long as the primary dist is not powered.

Would it be possible for both coils to work with the secondary but to still be bad?

Navaros911

Have you tried changing the ignition control units?

They are mounted just under the coils.

Check this thread: https://rennlist.com/forums/964-foru...placement.html

Navaros911

Just checked the price on those units... have they become much cheaper than they used to be... for 38 USD you could as well just get one to test with.

I'm sure there are better ways, but not for the time factor involved (for me at least).

johnsopa

I can run the secondary distributor using either coil and with either control module underneath. Wouldn't that mean that both control modules are ok?

wallra

testing the coils like you say means they are good. next your going to have to swap the distributor caps and rotors. did you try swapping the coil wires with your test? the wire that runs from the coil to cap

johnsopa

Yep, swapped coil wires a couple of times. Both coil wires would run the car via the secondary distributor. Neither would run the car via the primary.

I didn't want to swap caps/rotors because I don't like removing/reseating those plug wires too often.

But I think that's the next and hopefully final test.

Kappi2907

Replace by using the 993 coils.
2hour job Max