Testing Gen III Coil Packs

I have a mis. When I back off the throttle it pops. I've changed plugs. The problem is somewhat intermittent so I'm pretty confident it's electrical or electro-mechanical (not "mechanical" like backed up cats or something like that.)

My packs and harness were off a fairly high mileage car. I'm kind of suspecting the packs or maybe the pack harness, but I'm not sure.

I read a procedure for testing the pack for resistance.

Primariy resistance, Green - Black on the pack should measure .4-.6 ohms. I get squat. Secondary resistance, Green to output post should measure 5,000 - 7,200 ohms. I get squat.

But I'm confused (again). When I looked up OEM pack replacements, they said primary and secondary resistance is unmeasurable. Que? WTF?

I'm not even sure how to go about diagnosing the source of the problem. . .

Oh yeah, no codes are thrown. But it's obviously not firing on all cylinders. I suppose it could be a failing injector(s) or injector connection as well. . .

When you say "squat", does that mean zero, or no reading (infinite)?

Are the electronics built into the coil packs? If so, that does limit the ability to measure some things (the primary windings in particular) with a simple ohmmeter. Usually the secondary side is accessible for measurements, though.

69427 said:

When you say "squat", does that mean zero, or no reading (infinite)?

Are the electronics built into the coil packs? If so, that does limit the ability to measure some things (the primary windings in particular) with a simple ohmmeter. Usually the secondary side is accessible for measurements, though.

Click to expand...

Sorry, by squat I mean the reading doesn't change on the ohmmeter (multimeter reading resistence). If you touch the leads together you should get something around .5 ohms right? I tested on a relay I know is supposed to be about 85 ohms, so the meter and my extremely limited knowledge on this subject seems to be functioning. When I connnect the packs to the pins on the pack as described in a post on LS1Tech, I do not get any change in readings.

These are GM (Denso) packs. When I looked up the Duralast OEM replacement packs, the description stated primary and secondary resistance was unreadable. I don't think there would be any substantial difference between the Denso and the OEM replacement Duralast packs. I only mentin this is as I got what seems to be contradictory informatin; a description of how to read resistance from the packs and an indication that resistance is not readable from the packs (assuming the Duralast packs are functionally identical to the OEM packs.)

probably less painful to either buy one good coil or 'borrow' one from a buddy.... swap it around until you find the bad coil.
These things are expensive, the MSD coils are like $600.... :sos: ... if you buy those let me know if they're any good, I'm waiting to hear from someone who has first hand experience with these.

The general consensus on the MSD is not good. They have a tendency to fail compared to the OEM units, which are generaly pretty bullet proof. Also, I've heard from many tuners say the MSD are a nightmare to tune with; apparently because of that multi-spark "magic". As for OEM stye I only know of the GM units (Denso) and AutoZones house brand Duralast. The cheapest GM units I know of (brand new) are through Summit. The Duralast are still not cheap at $45/pc.

The stock coils lasted 130K+ miles on my '99 Z28, never had a problem with them, that's the main reason I was skeptical about the "magic" MSD coils and never bought them
Same for their plug wires: measured 30 Ohms on their wires and 300 on the stock GM wires - did not make a difference at all, except $50 less in my wallet....

You're sure the popping noise isn't normal ? My LS2 pops every time I back off the gas...

If it's misfiring it should throw a code.

It never popped before. . . Quite smooth actually. It's WAY down on power, not subtle. But strangely, no codes. It did flash on the fwy, but didn't set any code. That's wiird. It could be an injector or injector harness too I suppose.

Did you find a bad coil ??

IMO, fuel pump/pressure/flow/regulator is dirty.....clogged filter....

even the nagging problem that drove ME nutz for some time....water in the fucking GAS....just enough to cover the bottom of the tank and mess up your engine but good....:crutches::flash: