What else could it be? Missing

[phipps]

My son's 97 GMC with the 4.3 was missing so I replaced the dist cap/rotor and that fixed it for a few days. Then it got to the point you couldn't go over idle and I found that the coil was arcing against the ground so I replaced the coil. Again it was fine a day or two.

Now it's back to missing again, although not near as bad. I am not getting a MIL.

Could a plug have gotten fouled from the prior missing issues? I'm going to replace wires and plugs next. Is there anything else I should be looking at as a possible cause?

There is a sensor mounted on the same bracket as the coil. Does anyone know what it is? I was wondering if it could have been damaged from the coil arcing against the bracket.

[FishFind]

The sensor mounted on the bracket is the ICM Ignition control. you can take it off and have it tested for free at auto zone.

MAKE SURE you get acdelco plugs
I just went through this whole thing and you will waste your money if you get other plugs and have to buy the delco in the end anyhow
Also this is exactally what I had happen to my truck just about 2 days ago here is what the problem was for me "my distributor had play in it" not the cap the actual distributor. Take the cap off and see if you can wiggle the rotor at all left to right. Mine went a 1/8 inch each way so 1/4 total play. It should have 0 play at most 1/16 of an inch this caused me to have random misfire. Also same thing with me it caused my coil to arch and my wires. I never guessed that it was the problem but it was.

Here is my old post when I did mine. If you have play in yours it needs replaced. The gear on mine started to wear and allowed play. If you do replace it mark where the old one was at and also if it is not in position correctly it will not seat down. It has a notch in the bottom and it will not fit just on any tooth.

[FishFind]

http://www.automotiveforums.com/vbul....php?t=1063998
this is my old post. read that and see if it sounds like what you got going on

[phipps]

Thanks for the info. Reading your post sounds almost identical to my truck! Was your miss intermittent? I went out today and started it. It missed when I first revved the engine, but then was running fine.

I picked up plugs and wires today. I'll check the distributor when I change the plugs & wires.

I'm also going to have the ICM tested to make sure it didn't get fried. (the coil was arcing near the ICM)

[phipps]

Originally Posted by FishFind

Also same thing with me it caused my coil to arch and my wires. I never guessed that it was the problem but it was.

How would a loose distributor make the coil arc? I'm thinking I have a couple issues going on.

[FishFind]

not sure how it made the coil arch I thought that it must be something else because I was seeing arching. I think it is that it is sending the electric pulse to the dist but the dist is not on a terminal all the way so it needs to ground somewhere. Anyhow mine was arching same spot as yours and when I did the new distributor it went away and truck runs better now that it has in years.

Did you see if you had any play at all?

[phipps]

Originally Posted by FishFind

I think it is that it is sending the electric pulse to the dist but the dist is not on a terminal all the way so it needs to ground somewhere.

That does make sense.

I had to work this evening so I didn't mess with it today.

[FishFind]

ok. It may not be your problem at all but you can tell if it has play just but removing the cap and wiggling the rotor. If you get a new one and it still has a problem just go return it and tell the guy that you went to go change yours and found that your bolt was just loose and didn't need a new one. That is what the guy at my auto part store told me to do.

Yeah I really don't get why it would cause it to arch but it did and I can only guess why. I spent a lot of money replacing many things before that and prolly never had to. e.g coil 2 times wires 2 or 3 times and 3 sets of plugs

[phipps]

Well, I went out and started replacing the plugs/wires on the truck today. I pulled the cap and checked the rotor, sure enough it moved way too much!! Looks like I'm in for a distributor.

Thanks for the info!! I'd gotten the plugs/wires done and still had problems and probably would have ended up taking to a shop. You've saved me a ton of money!!

[FishFind]

Good deal. If you have not done it yet then note that the bottom of the distrib has a "key" in it and it will only seat if correctly aligned. If it wont seat you need to move it a notch.

[phipps]

I got a new distributor and dropped it in. It looked like it was not in the same position as the old one, but I could not get it to go where I thought it should be. I went ahead and put it together, but no go. Thinking maybe I was 180 out I switched it, but still no go.

I was able to find some very good instructions, with diagrams, online and got the engine to #1 TDC on the compression stroke and pulled the cap. The rotor was off by 90 degrees!

I pulled the distributor and turned the oil pump shaft and, after several tries, finally got it to drop in with the rotor pointing exactly at the 6 with absolutely no play. Put it all back together and she fired right up!

My theory is the gear on the replacement distributor was 90 degrees off from the old distributor. My mistake was not checking the old distributor against the new one to make sure everything lined up the same.

[FishFind]

Yeah I did that with mine also and had to set it to TDC. Did this fix the misfire?

[phipps]

The misfire is fixed!

I took it to a friend to check the retard and when he turned the distributor the gasket must have tore. It's leaking oil under the distributor now, but at least the miss is gone! LOL

[phipps]

Final update:

Took the truck back to my friend and he replaced the gasket for me. I was tired of working on this truck!! LOL

The truck is running great now.

Thanks for the info on the distributor gear! I would still be hunting down the problem if you hadn't pointed me in that direction.