94 3100 misfiring after plugs/wires

[ToroToro]

Hey all, I'm new here, and I figured this would be the best place to ask around about the crap my CS has been giving me lately.

Last night, I went out and bought a set of AC Delco plugs for it ( whatever model the book called for ), gapped em at .060 and threw them in. I figured it would run wonderful after looking at the old plugs which could very well have been original, or at least really old, but...

I started it and noticed that the idle was very rough. I decided to take it out for a ride, and sure as hell, the car was dragging major ass, and shaking badly.

So then I assumed the plug wires were bad, so I went to Autozone ( only place open ), and bought some "Ultra Spark" plug wires which I'm sure are garbage, but I thought they couldn't be worse than the originals...

But, that didn't correct anything. So I pulled all the wires off, made sure the plugs weren't cracked, and made sure I got all the wires on the right plugs.

I started it up again, it ran like crap, so this morning, I went out and bought some Autolite wires, which are at least halfway decent. but still it ran like crap.

Then, I decided to pull all the plugs and checked the gaps and whatnot, and sure enough, the #3 plug's insulator was in pieces. Bought a new plug and STILL it runs like hell!!! None of the other plugs looked broke or fouled.

So heres where I sit now...

- It sounds like it has a misfire constantly, although it is worse under load, at the lower RPMs ( 3000 and down ). When driving, I have to really put my foot down to get it moving, and even then, it's really surgey and rough...

- Have replaced wires ( twice ) and plugs ( once )...

- Plugs are gapped right, and wired right...

- All vaccum lines are attached...

-Threw a can of Seafoam in the tank, just to see if maybe the injectors are dirty...

- Never had any trouble before I did the plugs yesterday...

I'm thinking about getting another set of plugs, but I want to explore other paths too.

Any suggestions?

[bszopi]

RE: 94 3100 misfiring after plugs/wires

Coils. That's where I'd look next. Could be that the coils were going bad, but were still holding on with the old plugs. Then you put in the new plugs and it pushed them over the edge. Just a thought, but that's where I'd look next. There are ways to test the coils (do a search for coil problems) or you could just try jumping the plug to coil and looking for spark. Just don't get shocked too much!

[ToroToro]

Yeah, I thought about coils.

I have a good set from a newer 3800. Will they work?

[ToroToro]

Scratch that, I just went and bought new one.

We'll see how this goes...

[geoffinbc]

Why did you gap the plugs? They should have been gapped.

[ToroToro]

Yeah, they were. I just checked the gap before I put them in to be sure. The box said to "gap to specification" or something, so I wasn't too sure.

Anyway, right now, I'm swapping each coil out with the new to see if there is a difference. We'll see how it goes.

[ToroToro]

The new coils didn't make any difference, but it was worth a shot. If anything, it seems worse, because when I drove it after I did them, I had to pull over becuase it was running VERY rough, and blowing out rotten egg/fart smelling exhaust fumes. After a few seconds it miraculously stopped misfiring, and smelled fine. But then it started missing like normal again...

So I'm thinking ICM, crappy plugs or clogged cat.

Opinions?

Thanks a bunch, everybody.

[pepsi_coke]

If a coil is bad, its not sending the spark, yet, the cylinders are still being fed gas. That gas does detonate, yet still goes through the cycle. Dumpin raw gas into the exhaust makes the catalytic converter blazin red and eventually toasts the cat convert.

[red96beretta]

i don't mean to thread-jack but could that cause an 02 sensor related SES light ?

[ToroToro]

Not sure about the SES light, mine never came on.

At any rate, I went and pulled a used ICM, but that wasn't the problem.

Just when I was about to give up, I looked at the #6 plug when it was running and noticed some arcing. Turns out the damn plug wire boot wasn't totally over the plug. DUH!

So I just had to slide it over the plug more and it runs great now.

New AC Delco plugs- $10
2 New sets of plug wires- $40 ( took one set back )
Another new plug- $1.50
Can of seafoam- $5
New coil- $30
Used ICM- $10
Getting your 3100 to stop missing- priceless

Overall It was the most expensive tune-up I've ever done, but I suppose all is well that ends well.

Thanks for the input.

[TheDirtyBen]

ha!!!