Ignition woes (Page 1/1)
SavinJunk AUG 11, 03:04 PM
So I bought this 86 Fiero with the Iron Duke/5 speed combo. This ignition has absolutely giving me fits. The car has sat a while and had a noticeable ignition miss so I changed the cap rotor, wires, plugs, pickup coil, ICM and coil. I used Ac/Delco on the ICM, pickup coil and coil. It ran fantastic for about 50 miles then stopped getting spark. I found I had pinched the pickup coil wire under the cap but it didn't look like it broke the insulation. A friend suggested I use a better quality cap and rotor with brass terminals so I replaced those, and it fired right up. Ran great for about 50 miles, then quit again. So I thought I'd try a brand new complete distributor from Amazon. Started right up and ran great. For about 50 miles then quit again. The tach is jumping when I crank, the fuel injector is putting fuel down the throttle body, but no spark.

Could this be a bad tach filter?
theogre AUG 11, 06:54 PM
Iffy tach filter, ignition coil, even ECM getting hot can do this.

Remove the console and drive to see if problem stops/changes. If cooler ECM helps then is "dead" and save the PROM to move to new ECM.
See my Cave, HE Ignition & ECM Heat

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

phonedawgz AUG 11, 07:30 PM
Is the tach rising to 200 rpm during cranking and dropping back to zero after cranking? Or is it bouncing around during cranking. Bouncing around would indicate a bad ignition coil. Ignition coils can be destroyed by high resistance in the secondary or pulling plug wires on a running engine.
SavinJunk AUG 12, 02:03 PM
Great advice, I'll check that.

Has anyone on here ever swapped in one of the early Citation Iron Duke vacuum advance HEI distributors? Something I thought about to get to the traditional 4 pin HEI module.
SavinJunk AUG 13, 01:38 PM
So I found the problem; there was a hole burned right in the bottom of the coil. So now the question is, was this the problem or a symptom of the problem. Only other issue I could find was the plug for the hot/ground leads to the coil was really loose and wouldn't snap in place. I had another connector so I changed it. Maybe this caused it to overheat?
phonedawgz AUG 14, 10:57 AM
The secondary voltage will rise until it finds a path to ground. Normally that is via the dist, spark plug wire, spark plug and it's gap. If there is a reason the voltage can't find a ground the normal way, the voltage will rise until it finds a ground some other way. It looks like it found it's ground via a weak spot in the coil case.

PhatMax AUG 14, 07:28 PM
Looks like that coil has been replaced before…..
SavinJunk AUG 15, 11:17 AM
Yeah, it was brand new. I just put it on about 150 miles ago. The old one was good, I just did a full tune up when I got the car.

So far so good. I've been making some short trips and everything is still working.

One other issue I noticed; this seems to dump a lot of fuel in the throttle body on initial startup and chokes the engine. After a few seconds it smooths out and the spray looks normal. Anyone ever had that issue?