Lots of Misfiring?

[J. Henley 17]

My car has misfied since I got it a little over a year and a half ago... I've changed one of the coil packs, the spark plugs, and the plug wires, but it still misfires. Has anybody else had a problem similar to this?

I'd change the other two coil packs, but I'm not sure that it would help, since I already changed the one for the cylinder that was causing the problem, and I don't have money to just troubleshoot. I think I may end up doing that, though. But what else could it be?

[$*Blake*$]

my catylic converter was clogged and it felt like it was misfiring. tap it and listen if anything is broken

[BobbyZ72]

I had a 1999, the wires for the fuel injectors, and icm all had rub marks on them. The plastic was rubbed raw in some places with the metal wire showing and touching other stuff. Go back behind the engine and shake all the wires, see if this will temporaly fix your problems.

[Publican]

Check the Ignition Control Module that the coil packs sit on. It replaces a distributor in our non distributor equipped cars. The coil packs rarely if ever fail; the ICM is known as the weak link.

[BobbyZ72]

im bet its the same prob i had, the wires going into the ICM are all shorted out behind the engine with tiny rub marks. You might be lucky and just need to replace the icm, about 150 bucks if i recall right. I hope for your sake thats all it is.

[J. Henley 17]

Oh yeah... I had the ICM replaced, too... my car was nearly crippled that time. I can't think of anything else in the ignition besides the other two coil packs.

It's not just acting, it's actually misfiring... I get a check engine light and a trouble code for misfiring. It goes off sometimes, but not for long.

[BobbyZ72]

im telling you,, its the wires for the injectors and icm that are ran behind that engine... caused me to sell my 1999. Then friend who bought the car figured it out. Its going to cost $$$ to find the shorted wires and replace or repair them.

[J. Henley 17]

Behind the engine, like by the firewall? Yeah, I guess that should be lots of fun... I'll check them out, though, if I can... I think I've got a mirror/magnet that might work... thanks.

[BobbyZ72]

Between the engine and the firewall. I helps if you have a lift where you can easly get under the car. Let me tell you, this is not going to be fun. I dont remember how my mechanic fixed that car, but i think he had to remove the transmission to get right directly behind the engine. I dont remember, im sure you can look at your car and how they are ran. Like i said, i sold the car because of this problem pi**ing me off. One day i had enough and basicly gave it to my friend. Thank god my 97 has not had this problem.

[Razzer]

Take your car to a dealer and have them connect a tech2 while you drive it, that will show which cyclendar or cyclendars are the trouble makers. I just had the same problem, ended up being carbon buildup on the coil pack terminals. My dad being a gm tech, we replaces the wires with new delco's and 1 spark plug that had less than 10k on it. Fix all of my problems. ps I had very little backfire history, the tech2 in the missfire menu can run real time and that will show the trouble cyclendars while it doing it. Good luck.

[BobbyZ72]

When i was having the problem i took mine to the dealer. They drove it with the tech2 and said it need new plugs and wires and coil packs. I looked at him for a min and told him they where a week old. He says ok and drives it more and talks to other mechanics. He comes back to me and says the icm was bad. This is what i was thinking too, i ask how much to replace it, he says 425.00, i say no and i will do it myself. I buy the icm thing and change it out, CRAP same problem. The car would run fine sometimes, missfire othertimes. I walked down the street to a young girls house "16" who had always walked over and said what i pretty car several times a week, and told her it was for sale, cheap, she asked how much, i said only for the parts ive put into it. Air and fuel filters, cleaned throttle body, coils, plugs, wires, battery, tires, transmission filter kit, rear end gasket and oil. About 1 hour later her and her dad drive up with $1200.00. i told them the problem and they bought it. About 6 months later i bought this 97, so far no major problems. NOTE I HAD ONLY OWNED THIS CAR FOR ABOUT A MONTH, IT STARTED ACTING UP THE SECOND WEEK, I PAYED 6999.99 + TTL. It takes a lot to upset me this bad,, but this '99 managed to do it.

[3.4orNothing]

same thing,,,i got a small crack in the head gasket

[J. Henley 17]

Would the O2 sensor cause anything? One of the little brick things in my cat is rattling around, so I figure it's not functioning properly.

Anyways, the light has been off for a few days now. It went off Thursday afternoon, and I poured some fuel injector cleaner in it, and it's been driving fine since, but I'm really not sure how long that will last.

[Yaba3800]

same problem here. ive done wires,plugs, and coil packs. i hooked up a genysis modus scanner in my auto class and here are the general readings

cyl 1: few hundrewd misfires counted
cyl 2: 9221 misfire
cyl 3: few hundred
cyl 4: 1
cyl 5: hundred or so
cyl 6: few hundred

i ve done every tune up possible includeing all filters,

i just performed a cylinder balance test on it and that checked out. next up is a fuel pressure test. but i will check those wires behind the icm, too.

[BobbyZ72]

Originally posted by J. Henley 17:
Would the O2 sensor cause anything? One of the little brick things in my cat is rattling around, so I figure it's not functioning properly.

Anyways, the light has been off for a few days now. It went off Thursday afternoon, and I poured some fuel injector cleaner in it, and it's been driving fine since, but I'm really not sure how long that will last.

If you light is on you can get an o2 sim...or slim..or something like that and bypass that o2 senser after your cat. That o2 senser has nonthing to do with your engine...all it does is tell the computer if the cat is working or not. Plus the sim or slim is much cheaper then an o2