: '98 Deville Rough Idle, Shaking, Stuttering Under Acceleration

04-05-05, 09:49 AM
I have a '98 Deville that seems to be misfiring. About 1 year ago, the devilel started throwing codes indicating a misfire in one of the cylinders. I changed the plugs and wires and it became much less frequent. I got cheap wires and went against the advice to use AC Delco since they were so expensive. Well the sputter is back and worse (but no codes). On rainy days, it sputters a lot. The car will idle rough and is clearly misfiring. Under hard acceleration, you can feel that all cylinders are not firing properly be the stuttering. If you floor it, it will shake and then you can feel a burst of power here and there when it starts to fire properly, then when it shifts gears it bogs hard.

Any suggestions? Would it be worth it to change the wires again to AC Delco? Could that be the cause of the problem? Any way to diagnose the problem without going to a shop? Is there a way to deteremine if it is an ignition problem? By the way, it does not throw a check engine light now.

04-05-05, 08:39 PM
My 98 deville showing same problems, we're trying to work through it now on my thread. You can follow it at:


04-06-05, 11:36 AM
Try misting the wires in a dark place at night. That might give an indication if you see the wires arching. It didn't work for me, that's why I said might. I have heard (as you) many people say stay away from after market wires. Let us know what the outcome is. Curious minds want to know.

04-06-05, 08:59 PM
Wxman, it may be ignition coils like in my case. I had to replace a second one today. The good news is its real easy to check, all you need is a multimeter.

Goto the iginition coil (pictured in my thread), remove the two plug wires going to it and measure the resistance, should read between 5-10.

If you go through and check all four of the ignition coils like that, you may find that one of them read very differently than the others.

Still could be your plugs, wires, fule rail etc, but this is a real quick check and the repair couldnt be simpler.

post back your findings when you get a chance.

good luck

04-07-05, 01:40 PM
If you replaced the plugs and wires, even the cheapest chinese-sweatshop made ones will work. Maybe with more crosstalk than normal, but they should not cause misfiring...

Wxman, it may be ignition coils like in my case.

I'd definately start there.

04-07-05, 03:26 PM
If you replaced the plugs and wires, even the cheapest chinese-sweatshop made ones will work. Maybe with more crosstalk than normal, but they should not cause misfiring...

I'd definately start there.

This is not true. Cheap wires (and some expensive ones) will not work correctly from the very beginning due to electro-magnetic interference with the rest of the ignition system. The low voltage wiring from the crank sensors runs to the coil pack directly below the secondary ignition wires. If the wires leak current or cause EMI the signals will foul the crank sensor input from the crank sensors to the ignition module and cuase even more problems. Just because wires are new does not in any way guarantee that they are not the source of a miss or driveability problem. The OEM wires are not necessarily the only ones that will work but they are the only ones that are GUARANTEED to work because they were developed and tested on that particular application. Generic wires are just that....generic. They are made close to the correct length (if you are lucky) and that is about the extent of the testing and validation of them on that package. YOU are doing the testing and validation.

04-07-05, 05:01 PM
Get the OEM wires from some place you can return them.... Install them, see if there's any change. If not, it's not the wires, if so, keep them, and I'll eat dirt. ;)

But seriously, I'd really be interested in your results... All my cars have the cheap-o generic autozone wires on them, but I can't say that I haven't had any problems - I've had some suspicions, but am way too cheap to buy the OEM wires.. But if it fixes the problem, it might just provide the kick in the pants I need. ;)

04-13-05, 01:30 PM
last year my 94 STS starting running bad, I replaced everything: plugs, wires, O2 sensors, etc.....
My mechanic scanned it and came up with nothing useful. He did suggest to try replacing the fuel pressure regulator. As i was beginning to dismantle the top of the intake to get to the regulator I found my fuel injector harness melted on the top of the trans housing causing two injector wires to short against the trans (ground). I repaired the melted wire harness and tie wrapped it up away from the trans.
Car has ran perfect ever since then.

Check your injector harness........

04-13-05, 10:50 PM
Rick, my brother had the same thing happen on his 94 SLS. It gave him different problems. It ran bad but gave a MAP sensor code that didn't diagnose right. The insulation was coming off all the wires just above the connector by the trans

Cruella Deville 96
04-17-05, 07:55 PM
Dear Gentlemen, BBobynski is right. As an Electronic Engineer, his explanation is right on the mark.

I just changed plugs and wires in my '96 Deville, and found fresh oil dripping off of one of the front sparkplug ceramic insulators! Obviously, the minimum-wager at Jiffy-lube has done it to us again. When filling with oil, some got onto the heads, seeped down into the sparkplug well, and just sat there...waiting for a current to short to the block.

This is my second post to this group, and even though I have the factory shop manuals, We, my wife and I, have learned so much!!!

Thank You!

Only use AC Delco wires and plugs. Mr. Goodwrench was right after all.
Scott in Anchorage.