How do I test a coil pack?
05-03-2008, 03:28 PM
#1
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How do I test a coil pack? Ok... here's the situation. 2000 Camaro, new shortblock, heads, and GT-11 cam @201,500 miles, ran great on stock tune... Mac headers @ 212,000 miles, started misfiring under heavy load.
I didn't know anything was wrong with it until it went on the dyno at G-Force. It "banged out" above 3500 RPMs. We checked the plugs and replaced the wires to no avail. I've checked the plugs again since then. There are no DTCs because G-Force deleted the misfire tables (Why they did that while they new I was having a misfire problem, I will never know). So I have nothing to go off of except that I know its getting worse, and seems to be worse when the engine is hot. It was unnoticable during regular driving, now it shudders in 6th gear, or at low RPMs in general. It's also causing exhaust backfires even at idle. All the fuses and plugs have been checked. My eyes are on the coil packs because they're 213k miles old.
How do I test a coil pack off the car? I can't swap it to another cylinder, because I don't have misfire tables to read. G-force is 3 hours away, or else I'd just have them restore the tables. I tried search, didn't find anything. I'd rather not have to drop the dough to buy ALL the coils.
I didn't know anything was wrong with it until it went on the dyno at G-Force. It "banged out" above 3500 RPMs. We checked the plugs and replaced the wires to no avail. I've checked the plugs again since then. There are no DTCs because G-Force deleted the misfire tables (Why they did that while they new I was having a misfire problem, I will never know). So I have nothing to go off of except that I know its getting worse, and seems to be worse when the engine is hot. It was unnoticable during regular driving, now it shudders in 6th gear, or at low RPMs in general. It's also causing exhaust backfires even at idle. All the fuses and plugs have been checked. My eyes are on the coil packs because they're 213k miles old.
How do I test a coil pack off the car? I can't swap it to another cylinder, because I don't have misfire tables to read. G-force is 3 hours away, or else I'd just have them restore the tables. I tried search, didn't find anything. I'd rather not have to drop the dough to buy ALL the coils.
05-03-2008, 07:47 PM
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Pull the wire from the sparkplug and connect another sparkplug to the wire. Ground the electrode and have someone crank your car over. You should see a spark if its working. Or get your car hot and let it sit there idling and misfiring for a minute or two, the squirt the manifold with a little bit of water right by each exhaust port, the one that doesn't evaporate the water as fast is the one in trouble. Hope one of these works for you.
05-05-2008, 11:44 AM
#5
fwiw my old man has a lincoln town car with 350k or 380k miles on it, coil packs started going on it around 350 miles, at about 1 every 2 months or so he would find another dead or really bad coil and have to replace it. going off that I wouldn't necessarily think 200k is the failure point for coil packs.
one way you can test them is measure the impediance on the coil, should be something like 0.5 to 1 ohm, but this only tells you if the thing is good or bad. The coil on the running hot engine is a completely different environment and if you don't focus on that you are wasting your time. heat is bad for a coil and can make them fail intermittently, until they cool off. unfortunately the only real good way to check is with a full blown diagnostic monitoring ignition on every cylinder with a scope, and waveform charts will show injector pulse widths, coil firing and all that **** and you can pinpoint the problem instead of throwing parts and money at it.
What you might try is get a DTC and find out which bank it's on, then swap the coil packs from left to right and see if the DTC moves over to the other bank.
this is assuming you have good plugs and wires and your plug gaps are good.
one way you can test them is measure the impediance on the coil, should be something like 0.5 to 1 ohm, but this only tells you if the thing is good or bad. The coil on the running hot engine is a completely different environment and if you don't focus on that you are wasting your time. heat is bad for a coil and can make them fail intermittently, until they cool off. unfortunately the only real good way to check is with a full blown diagnostic monitoring ignition on every cylinder with a scope, and waveform charts will show injector pulse widths, coil firing and all that **** and you can pinpoint the problem instead of throwing parts and money at it.
What you might try is get a DTC and find out which bank it's on, then swap the coil packs from left to right and see if the DTC moves over to the other bank.
this is assuming you have good plugs and wires and your plug gaps are good.
