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1992 Cadillac DeVille 4.9L
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Discussion Starter #1
Today I replaced all my spark plugs, wires, distributor cap and rotor. I took her out for a drive, and when I floor it from a stop, it stumbles and stumbles...and then violently kicks the tires loose. It even happened sometimes when I floored it at higher speeds. Would stumble, stumble, then kick hard.

What did I do wrong? It also idles very roughly, and stumbles at idle in drive with brakes on.

I thought this would make the car run better, not worse.

Also, I did have some annoyance with the wires. I got MSD 8.5mm's, and they were a ***** to get onto the plugs, and the distributor.

All the plugs are properly gapped, and I'm sure they're not the problem. Could I have done something wrong with the distributor/wires?
 

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'98 Buick Regal LS - '91 Caddy Seville - '87 Caddy Seville!
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What all have you checked thus far?

I would go through all that you have replaced and make sure everything is fine. Make sure that you have not mixed the firing order when you replaced the plug wires. Also examnie the new cap and rotor for cracks that you may have caused when replacing them: this happened to me the other day when I had to replace the coil...I wound up replacing the cap too! Check the plugs again for cracks as well. It is possible that when struggling with the plug wires, you may have cracked a plug in some way.

Post back and let me know the results...
 

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1978 Seville, 1979 Seville, 1979 Seville diesel, 1980 Eldo
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142 Posts
Most common mistake when doing a tune-up...over-tightening the coil! Check for a screw that went ALL the way through the cap...spark will jump right to that screw!

FRANKO
 

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1992 Cadillac DeVille 4.9L
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203 Posts
Discussion Starter #4
One corner of the coil (the one with the little ring that leads to the terminals) was stripped by me...I don't know if it went through, but that could definitely be the problem.

What can I do, if I did do that?
 

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'98 Buick Regal LS - '91 Caddy Seville - '87 Caddy Seville!
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4,425 Posts
In that case, the cap will need replaced because the screw likely busted through. I would inspect the cap for sure...It should still be under warranty though, and hopefully they'll exchange it.

This happened to me just about a week ago; I over-tightened the screw on an Accel Supercoil and it went through, and like Franco said, it was charging the screw and not the plug wire...
 

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1992 Cadillac DeVille 4.9L
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203 Posts
Discussion Starter #6
will they send me a new one if I overscrewed?

It stripped really easily, if that matters...
 

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1992 Cadillac DeVille 4.9L
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203 Posts
Discussion Starter #7
I'm going to try switching my old cap back in, and seeing if the stumble goes away. If it does, I'll try to get a refund.
 

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1992 Cadillac DeVille 4.9L
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203 Posts
Discussion Starter #8
The stumble is still there, but less evident now. It responds faster with the old cap, but still stumbles, which it DIDN'T do before I replaced plugs/wires/cap/rotor.

ARGH!!!!!:thepan::bonkers::hmm::alchi::mad:
 

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1992 Cadillac DeVille 4.9L
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203 Posts
Discussion Starter #9
This is REALLY pissing me off. I had the car running fairly well before I did this "tune-up," and now it runs crappy. Worst idle it's ever had, and the stumble when I try to accelerate rapidly is very frustrating.

The idle is just as bad with the old cap, but the stumble is a little better. Still does it, but not for as long.

I think I'll send the cap in...it was a cap/rotor kit. I don't want to send both...ugh.

Is there some simple solution? Dielectric grease?! Ugh..!!!!!!!!
 

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122 Posts
Something is definitely wrong. If you havent already done it at least twice, I would check to make sure you got all the wires going to the right cylinders. This happened to me when I changed mine. I was sure to pay extra attention to where the wires went and I still got #7 and #3 mixed up.

I was amazed when I found out what was wrong that the car still ran so well with the wires mixed up. Not that it ran well, it was stumbling and really rough but it would drive. I just thought if you had the wires mixed up you wouldnt be able to drive it.
It took me checking the wires three times before I noticed it.
Anyway just a suggestion.
 

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1995 FWB 128,*** miles
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2,257 Posts
pimpdaddycaddy91 said:
Something is definitely wrong. If you havent already done it at least twice, I would check to make sure you got all the wires going to the right cylinders. This happened to me when I changed mine. I was sure to pay extra attention to where the wires went and I still got #7 and #3 mixed up.
I was amazed when I found out what was wrong that the car still ran so well with the wires mixed up. Not that it ran well, it was stumbling and really rough but it would drive. I just thought if you had the wires mixed up you wouldnt be able to drive it.
It took me checking the wires three times before I noticed it.
Anyway just a suggestion.
Ditto. Happens all the time...
 

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1992 Cadillac DeVille 4.9L
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203 Posts
Discussion Starter #12
Good plan, I shall do that right now. I did check twice, but it's entirely possible...
 

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1992 Cadillac DeVille 4.9L
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Discussion Starter #13
I checked...triple checked, quadruple checked...


What is the orientation of the cylinders.

Facing the engine from in front of the car, the left closest cylinder is one...right?


2468
1357

Right?
 

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1992 Cadillac DeVille 4.9L
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203 Posts
Discussion Starter #15
I did. Checked, triple checked, checked again...I'm pretty sure they're right.
 

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1992 Cadillac DeVille 4.9L
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203 Posts
Discussion Starter #17
I don't see how it could be anything but the plugs/wires/rotor/cap. It just idled rough before, now it stumbles. :crying2: and idles really crappily
 

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1989 Sedan DeVille is now just a fond memory ....
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10,429 Posts
Just a couple of stupid questions;
I didn't notice what year and engine you have, can you identify?
What brand/model spark plugs did you install?
 

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'90 DeVille '97 DeVille
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83 Posts
Just a thought: Make sure the tubes/vacuum lines running to the air cleaner housing are secure and not cracked/broken. Make sure a rush of cold air is not entering the engine thru a tear/break in the "bellows" heading into the air cleaner. These things can drive a person nuts! Been there!!! Good luck! Matt
 

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1992 Cadillac DeVille 4.9L
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203 Posts
Discussion Starter #20
Is the only vacuum tube the one that connects close to the TB, behind the snorkel? The part that attaches is kind of broken...
 
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