Car won't stop misfiring

[99firebird]

well this is the story,,, i've had this misfire for a few months now,,, took it to the dealer and said my fuel injectors were clogged and i also new that i had a bad cat( warrenty) and they changed that too,,, they also gave me a new pcm for free ( they said something was wrong with it).
they said the coils were fine. after all that I STILL GET A MISFIRE, i don't know what it could be. i've changed the fuel filter had plugs and wires change like four months ago.... another thing that i noticed was when i ran my car through the car wash, it was misfiring badly,, ses light was flashing, after driving it for like 10 minutes it went back to normal ( only misfiring during heavy acceleration). so if you guys have any ideas or advise let me know...

thanks

[99firebird]

another thing i took my car to auto zone and it was cylinder 1 that was misfiring,, but my ses light was blinking, i thought this meant that it was multiple cylinders misfiring....

[gig]

Hello all--

I posted a similar message months ago. This is a long one, so be prepared...

This misfiring thing is a common problem. I know, I was battling it for almost 2 years on my 97 Firebird. I've replaced the plugs 6x, wires 4x, all 3 coils, ignition module, fuel filter, cleaned the injectors, etc. You know what, even the mechanics (independent, friend, and dealer) couldn't solve this problem--and to think of all the money I wasted on replacing parts. So I did my own research, and solved it myself.

Due to the design of the cars, with the engine sitting under the dash, and the fact that the 3.8 V-6 is 90 degrees (less room on either side means less ventilation) and cast iron (retains the heat more and stays hotter), the underhood temperatures of our cars are incredible, especially on the passenger's side where the exhaust manifold is. The heat destroys the ignition wire, which is why GM was replacing them, although they won't tell you the heat is the reason. What happened to mine is the extreme heat burned/cracked the spark plug boot on wire #6, and these were MSD wires. This caused my misfire, and from the looks of it it must have been cracked/burnt for some time.

Here's what you'll need:
1) New set of spark plugs if yours have over 20,000 miles on them. I have Autolite racing plugs, although the AC Delcos, NGK, etc. will work fine. Avoid Bosche--I've heard of many problems with them on these cars.

2) New set of high quality spark plug wires, a universal set you make. I highly recommend MSD 8.5mm Superconductors, as these are very well made. The boot that burnt on mine was due to the extreme heat--the wires themselves are excellent.

3) Spark plug boot protectors, such as Design Engineering's Protect-a-boot #010501 (silver, reflects heat better than the colored ones). You'll need 6 of these.

4) Spark plug wire heat sheathing. I got mine from Napa, and it will protect the wires up to 1500 degrees or so. Excellent stuff. Other companies also make this as well--just be sure it's the high quality stuff.

Here's what to do:
1) Remove and replace all 6 spark plugs, if yours have over 20,000 miles. Don't take out the wires yet. If you have the factory metal heat protectors for the boots--remove them, as you will use new ones that will cover the boot completely.

2) Be sure the wires are still in the looms on each side of the engine. Mark with a felt pen where each wire meets the wire loom. The distance you want is from the spark plug boot end until where it meets the wire loom.

3) Loosen both wire looms so the wires come out. You may need to purchase a new loom (Made for you has excellent looms that do not warp from the heat) or modify the factory ones to fit the larger wires.

3) Remove the #6 wire first. This is the one that gives the most trouble, as it is nestled under the dash, exhaust manifold, and near the AC stuff. Due to the extreme heat and lack of ventilation, this one will burn/crack, causing a misfire since the energy is being grounded elsewhere.

4) Cut heat sheathing the length from the spark plug boot end until the mark you made where the wire meets the wire loom. Install this heat sheathing over the wire until it meets the spark plug boot end. Install the "cloth like" spark plug boot protector over the boot as well. When you are done, you'll see that the boot/wire is fully protected from the spark plug until the wire loom. Thus, the heat will not damage them. Install the other end of the spark plug wire. On the MSD universal wires, this is the coil end.

5) Continue with the rest. I used the heat sheathing on #6, 4, 1, and 3 wires. #5 and #2 wires, from the boots until the wire looms, are short and not under extreme heat, so they don't really need the wire sheathing. You can, though.

6) I used the boot protectors on all 6 wires. On some cars, the factory had metal boot protectors. This didn't work, since when the boots cracked the arched against the metal protectors. My car didn't come with these, and you won't need them. Design Engineering's Protect-a-boot covers the entire boot, thus giving it much better protection.

7) Once completed, put the wires back in the looms and fasten down. As I mentioned before, the MSD wires are 8.5mm, necessitating modifying the factory looms. I just used new 2-piece looms from Made For You that I added a longer bolt to and bolted in the same holes as the factory looms.

This should solve your problem. If I only did this sooner, I would have avoided replacing so many parts. The dealers nor independent mechanics couldn't figure out the problem either--if you went to them they would have you replacing parts you didn't need to replace.

I hope this helps--drop me a line if you have further questions. My email is gig229@yahoo.com, and my name is James.

[pvtschultz]

Very excellent post. My car fries the wires about once a year, and that will save me big money. Come the next time, I'll be prepared.

BTW: a blinking SES just means you have a missfire, the computer will tell you which is the culprate.

[ March 15, 2003: Message edited by: pvtschultz ]</p>

[Takumi Fujiwara]

I was lucky, I had a missfire and it was actually just one bad wire, ( not burnt ) just no longer was able to transmit electricity. Turns out I know at least on 97s there was a recal on spark plug wires in 99. when my wire went out recently I tried to get the local and retarded dealership to honor it but they wouldnt, turned out pontiac gave me a 100 dollar check to help with the damages cause I took it to my mechanic and he chagned all the plugs and wires and checked all my electrical , fuel pumps and cylenders ( pretty much everything to do with a possible missfire ) for 120 bucks.

[cb1101]

I'm guessing I will be dealing with this problem again very soon. Less then 6 months ago I changed my wires cause i had misfires up the a$$.

Now everything is fine until I drive it for more then say 20 minutes at a time...engine is nice and hot, then under heavy acceleration, i feel the same bogging/banging that i used to feel 6 months ago.

This only happens after driving for a while.

[Dekay]

Ok so here's my question. I had new wires, plugs and ignition coil console (mechanic thought that was the prob) put in a month ago. After about 200 miles of driving, I get a missfire on cylinders 1 and 3. I went to Autozone, reset the computer and 200 miles later it comes back. I don't feel any studdering or anything that would make me think there's a misfire. What else can I look at?

[RUC]

check your fuel pressure, I had a misfire due to a bad fuel pump

[gig]

I've been reading some of these replies on this misfiring thing. Believe me guys, I battled this problem for almost 2 years. If your car starts to misfire when it heats up, that's telling you something. Excessive heat will cause more resistance in the wires (energy going to plugs). My car misfired a lot more when it heated up. If you have cheap wires and/or plugs, change them to the quality stuff. Yes, the good stuff costs more but in the long run will save you money. I strongly suggest adding the Protect-a-boot spark plug boot protectors and wire sheathing--the heat will destroy the wires/boots eventually if you don't. Believe me, I know. If you're car is misfiring due to arching (like mine did on #6 boot, which was split and burnt), this will eventually ruin your ignition module and possibly your coil(s), costing you more money. This is what happened to me before I added the protection for the boots and wires. Our car's engine location causes excessive heat, which destroys the wires. Adding protection to the wires/boots will protect them and is the first line of defense against this problem.