Misfire cylinder #1

[aleromgf]

Hello, All

Alero 2001
2.4L
115000 Miles
Auto Trans

Problem started last week, car developed serious stumble, and after checking I found the coil pack housing (white oem) had a 1.5 inch long line of carbonization on the side, a sure sign of arcing.

Replaced housing with a black one from Advance Auto Parts, and car ran fine for two days.

Then the same problem again.

I replaced the plugs, and found that two of them, I think #1 and #3 had the center electrode almost completely eaten away. No change.

Then i replaced the ICM, Coils, and now, after numerous tests and rigging, I can see that all spark plugs fire when they are outside the engine, but apparently not when they are inside.

I say this because plug #1 looks absolutely clean, with a slight film of gas, and all the other 3 have some slight carbon deposits and they also smell faintly of gas, though they are dry.

(These spark plugs are new, they have only ran for about 2 or three minutes while testing this problem)

Any thoughts?

Thanks for any help.

[clutch1]

Stupid question, but after all the new parts did you replace the wires?

Cam sensor working properly?
ICM gettin proper power and ground?
Coils getting proper power and ground?

That's tricky, that's really all I can think of.

[aleromgf]

Hello, clutch1, thanks for responding.

No wires on 2.4L

ICM is getting proper power and would seem to be properly grounded, but have not verified the circuit.

Coils do have stand by power at 12vdc., however, it is difficult to tell if they are getting a good, closed ground when the ICM charges them.

At first I suspected a bad coil, but I am puzzled by the apparent fact that the plugs fire fine outside, but apparently #1 does not fire once inside the cylinder.

[Nate's Alero]

the little boots on the IDI cover.. replace them, they never last forever

friends cavilier, they were bad, sounds like the same thing

[Midgear]

would compression be an option? check compression in cylinders 2 3 and 4 vs 1.. see what happens?

[clutch1]

Ah yes, that goofy cover thing on the 2.4! Forgot it was setup like that.

Those are coil on plug designs, right? So like 4 different coil. I was thinking it had coilpacks, like the kind where 2 plugs are linked per pack.


First check the boots like Nate said, if a boot's cracked AT ALL, even a tiny bit, it's most likely arcing again. Make sure the plugs fit snugly into all the coils and there's no metal showing where the spark could escape and jump to the block. I'd probably replace the boots anyways.. they can't be that expensive..

If all those check out then I got a few ideas..


For the record, I'm pretty sure you need to unhook the energizing circuit to the coils that aren't being.. so they don't arc.. IIRC. If I'm wrong please let me know, lol.. just don't wanna mess anything up

Anyways, how are you testing it off the car? Spark tester I assume?

If they're all working correctly off the car w/ a spark tester (which is what it sounds like), use the tester to verify that each coil is putting out roughtly the same amount of voltage.. like all around 20,000V (approximate.. it varies car to car) (should be.. they're brand new!).

Once you verify that they're all working properly, that narrows it down to the plugs. Take out the plugs, and grab the one that's misfiring. Pick one of the coils and attach it to that. Now, ground the threading of the plug to the car's frame (not the engine block!) (normally threading into the block grounds it.. this is like the same, just outside the block.).. now test it again, and verify that it's sparking properly.
Test the other 3 coils like this as well. If you'd like to be thorough.. test all 4 plugs on all 4 coils to make absolutely sure nothing could be wrong.

If everything check out OK, try grounding them to a bolt on the engine block now... if you run into a problem, this means you probably have a bad engine ground.. either find the stock one and clean it up, or add a nice thick piece of wire from the block to the frame of the car.. that should clear it up.

If they work OK when you ground them to the engine block for testing, check the threaded holes for the plugs.. make sure there's no junk in there that would cause a bad connection.

Remember, that the high pressure of a piston compressing will make it MUCH more difficult for a spark to arc.. if all of them arc outside in just atmospheric pressure, that doesn't mean they'll arc for sure in the block... this is why if a spark can get through a crack in the boot to the block, it'd rather do that than ignite the plug.. If a coil is weak (shouldn't be.. if they're brand new), or a bad connection, it'll be too difficult for them to work in a running engine. If compression is low, technically it'll be easier for them to ignite, as well. Low compression is bad, but shouldn't make the ignition system show any symptoms. If everything checks out good (good boots, all equally powerful votages, good grounds, clean connection on plug holes), I'd rule out ignition and check for cylinder leakage.

That's all I got.. good luck

[aleromgf]

Nate's Alero, I forgot to add that I had also replaced the boots and plastic clips.

Midgear, Yes, it might be a comp issue, but keep on reading...

Clutch1, Thanks for all your ideas, I had tried some of them already, but I had not thought of engine ground and it may be part of the problem. But read on, and check this out:



What you see above is my latest attempt at diagnosing this problem. As you can see from this pix, I am isolating and removing the housing (brand new) as a possible culprit, and also eliminating the possibility that the coils, or their supply wiring, are being grounded.

I removed the coils from the plastic housing and insulated them from the metal IDI cover. I rigged my test cables to run directly from the coils to the spark plugs, thereby eliminating several possible paths to ground.

I also directly connected the ground strap on the IDI cover to the battery ground.

Guess what? my baby is working again!

So, the only thing this proves, is that it is not a compression problem, but just ignition.

I will continue to isolate it until I can give you all a definitive answer, but a few things are possible:

Defective (brand new) coil housing.
Defective supply wiring to coils. (that may be grounding when everything is put together the way it should)
Lack of good ground at the ICM.



Thanks for all your help!

[clutch1]

So the misfire is gone for now? That's good to hear! Let us know if anything new comes up or if it starts again man!

[NickAlero2000]

Ive learned the ground on the 2.4 sucks, this issue happens to EVERYONE with the 2.4 at some point unfortunately, but such is our car...
glad it seems cured for now...let us kno if it comes back!!!

[spyhunter]

easiest way to get past the problem, buy some spark plug wires for a 2.2L cavalier, MSD coil packs, interface modules and call it a day.

[[ion] C2]

Originally Posted by aleromgf

I also directly connected the ground strap on the IDI cover to the battery ground.

Guess what? my baby is working again!

So, the only thing this proves, is that it is not a compression problem, but just ignition.

I don't even have the ground strap on my IDI cover. The ICM is grounded with a wire on its own, the strap is unnecessary.

[aleromgf]

OK, after much testing and experimentation I concluded that as hard to believe as it may be, that the coil pack housing was bad (again) and replaced it with an OEM housing.

Car has been running 2 days so far.

[Nate's Alero]

hope it keeps running