: Ignition quirks with built Northstar



Will's Fiero
11-24-10, 06:21 PM
Frequently at idle and occasionally under load below 2000 RPM, my Northstar will have what I call an "ignition dropout".

The tach will drop instantly by several hundred (up to 500) RPM. This does not represent an actual change in engine RPM, as the engine continues to spin. It appears to represent a momentary loss of signal to the tach. If this happens under load, the car jerks unpleasantly. About 50% of the time this happens at idle, the engine stalls. The stall saver routine in the ECM catches it the other 50%, but this results in an idle surge. I have never known it to happen above 2000 RPM.

I'm going to be troubleshooting the ignition power circuit over the weekend.

Is this a symptom of a common failure mode in Northstars? Ignition module? Coil(s)? Crank sensors?

The engine is bolted up to a 5 speed transmission and installed in an '87 Pontiac Fiero. I did the wiring myself and am confident in it, although the car has been off the road for a while as I built the new engine for it.

Thanks!

Submariner409
11-24-10, 08:53 PM
What year engine is this and are you running it with the OEM ECM/PCM or an aftermarket stand-alone system ?? Crank/cam sensor failures happen, but in the overall scheme of things are not common. You're in a modification area that few owners here have ventured into - your best bet is a Fiero-building member - AJXTCMAN - or CHRFAB. By your own admission the engine is a hodge-podge of several years of parts - difficult to even take a SWAG (Scientific Wild Ass Guess) at the problem(s).

Will's Fiero
11-25-10, 09:51 AM
Ooops... I guess it would help to know that I have a '95 computer. Obviously I have a coil pack ignition and appropriate crank/block selection to go along with that or it wouldn't run at all.

The rest of the part selection is irrelevant.

It ran well and did not have this problem when I last had the swap running in '04. Something has degraded in that time. I'm going to troubleshoot my own wiring.

I was just wondering if "ignition drops" with symptoms as described were an indicator of a common failure mode on Northstars.