When driving on the hwy, after 10- 15 minutes, the tach will drop suddenly but will pop right back up. this lasts a fraction of a second. Too long to be just a miss as the engine goes through quite a number of revolutions before it catches again. It's as if I suddenly "flicked" the key off and on really fast. occurs randomly. In all types of weather (I am in Tampa FL by the way). Its slowly geting more frequent.

Replaced the ignition module a few months ago with a "premium" BWP unit. Used thin film of computer CPU high end thermal paste. I did get some of it into the screw holes (don't they also ground the module?) car ran progessively bad, missing more and more until i pulled out the module cleaned out the holes and from around them. ran fine for over two mmonths until this started. Last module said goodby by having three over a second cut outs and then nothing. Just wondering also if I could have damaged any ignition components by running with a very poor ground when the past got in the holes. Ran it for 4-5 days by the time it got bad enough to be obviously missing and down on power. Wondering because if i damaged other componnents, I need to know which ones to look at for replacement.

Thanks

So your problem is going to be one of the primary ignition components. These components are

ICM
Pick Up coil
Ignition coil
The short cable between the ICM and the ignition coil
Power to the Ignition coil
and
The magnet in the rotor of the distributor.

Since you replaced the ICM and that didn't fix it we can eliminate that one, at least for now.

The easy tests -

With the engine running wiggle the wires coming from the harness to the ignition coil. If it cuts out you have the the problem found.
Next try the cable between the ICM and ignition coil. Again if it cuts out you have it figured. btw, I sell these new on my website if you are interested - http://www.reddevilriver.com/2.html - I am less expensive than the Fiero store.
Next if both of those make no difference take a screwdriver and knock the metal base of the distributor while running. If the engine coughs then I would expect the pick up coil to be the cause of the problem. The pick up coil tends to go bad over time. The glue falls apart, the insulation fails and the whole thing looks like it is failing.

If you find nothing with the easy tests then you should use an ohm meter and test the pick up coil with the meter.



Note - you don't need to remove the distributor to test the pick up coil. You do however need to remove the distributor to replace the pick up coil.

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In case you need it - replacing the pick up coil

Removing the distributor


Replacing the pick up coil




Replacing the distributor



Timing the engine after replacing the distributor into the block





Videos by BuddyCraigg

[This message has been edited by phonedawgz (edited 05-06-2014).]

quote Originally posted by phonedawgz: btw, I sell these new on my website if you are interested - http://www.reddevilriver.com/2.html - I am less expensive than the Fiero store.

THANK YOU I've been looking for an already put together one of these cables!! All my clips broke and one of my pins keeps becoming recessed in the ICM part!!! Is that some sort of silver heat wrap in the picture?

Yes that is reflective heat tape. It wraps around the high temperature wire loom just like the original.

The metal terminal pins load from the front on the ICM connector. They are not supposed to travel past the flush point. The inside of your connector must be junk.

[This message has been edited by phonedawgz (edited 05-06-2014).]

My engine was cutting out and it turned out to be a bad TPS. Just an idea. But it was like it cut out for a millisecond , not for a few revolutions. Seems like yours is probably more ignition related due to your issues with the ignition beforehand.

------------------
===Always trying to find time to work on cars===
Louis Duet
Baldwin, Long Island, NY
Where driving hard is SOP.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
"Blue" <= '85 Fiero GT
Stock V6---Stock everything. Trying to keep it 'mostly' that way.
~~~~~~~~~~~~~~~~~~~~~
"Boo" <= '81 Delorean DMC-12
The "DuetLorean"
VIN #5835
Stock PRV engine
Robertson Equipped
Neiland/Delman Engineered
Carbed and loving it! (Peugot 604 manifold) ---"Sorry purists"

My money would be on the short cable mentioned above. Had this happen on my car twice. Last time I went on line and bought a brand new cable and kept the olde ones for emergencies.

quote Originally posted by phonedawgz: The metal terminal pins load from the front on the ICM connector. They are not supposed to travel past the flush point. The inside of your connector must be junk.

Phonedawgz, do you know how sturdy or what exactly holds the terminal pins in place? There is someone who is telling me all I have to do is push the right wire (the recessed pin) in and I'll have no issue. While the car starts I'm afraid it keeps jiggling loose because I'm having some hard starts and a car that acts like it wants to die idling but hardly ever does.

Phonedawgz, thanks for the full guide on how to troubleshoot my ignition issue. a + for you for really putting forth the effort and time. I'll get on this today if i remember correctly where my ohm meter is resting.

Had a random cut out / shut off once. Just by accident, discovered a wire bundle had come loose and was hanging low enough to be rubbing on the axle. Had worn through the insulation and was causing a random short. Ya never know!

quote Originally posted by PribanicS: Phonedawgz, do you know how sturdy or what exactly holds the terminal pins in place? There is someone who is telling me all I have to do is push the right wire (the recessed pin) in and I'll have no issue. While the car starts I'm afraid it keeps jiggling loose because I'm having some hard starts and a car that acts like it wants to die idling but hardly ever does.

The connector for the ICM uses 'pull to seat' terminals in the plastic connector. The plastic connector is what holds the pins in place. It is supposed to hold the pin in place from pulling in to the plastic too far. If the terminal goes into the plastic connector too far the plastic connector is what is at fault.