Cylinder 8 Missfire

[davidz28]

I just developed a missfire on cylinder 8, before i get my car to the shop to check out the problem what are some probable causes? I put longtube headers on recently and it has ran fine until this point i also changed plugs while i was at it. The plug wire does not look melted from up top but could be underneath.

[2002ssslp]

This is the drivers side rear plug. Even with LTH you have room to work with. You will have to trace it back. Make sure the wire is connected properly, if they are old wires then ohm it out to see if that is the prioblem. Pull the plug again and make sure it is not fouled or cracked. Then you have the coil to deal with. I think another member could help you out with that test since i do not know the specs for a stock coil. I think that should help you find the problem. Good Luck !

[cammed goat]

Some will say switch the wire from number 8 with number seven and see if the issue changes with the cylinders as well as the coils. Swap the coils from 7 and 8 and see if the issue swaps from number 8 to seven. Keep us posted.

[SMWS6TA]

I would stay on the same side, switch from 8 to 6,4,2 so that I wasn't going back and forth. Either way it will let you know if it's your coil, wire or plug is bad.

[tatertot91]

Yup thats the best way to trace the problem. I would start with wires as thats the easiest thing, may as well check the plug for the hell of it and then move onto the coils

[SMWS6TA]

on a different car I had a similar problem. It was like it was a ghost code. Popped up when ever it wanted too. Seemed it would only do it on a heavy load. When I pulled the plug I didn't see the hairline crack, but the second time I moved it back to the problem cylinder it feel apart. Replaced it and all was good. Sometimes the cracks just aren't obvious.


This was before there were forums like this online.

The worse trouble shooting experience I had was with my 96 Firebird. It would run rough, misfire, codes popped every week, either I would blow plugs, wires, or occasionally a coil pack over an 8 month period . Then I went to Korea for a yr and then got deployed to Iraq for another yr, so my wife just let it sit and she would run it at idle for 10 mins per week. During that time I research the hell out of this problem. I replaced everything coil packs, plugs wires. Then I came across a TB from GM that said to replace the plate that the coil sit on ever 70k miles due to it will cause shorts. I get back and do so, car ran like it return from the dead. I instantly could hear a see a difference. Wife asked me if all was good, I tore off a section of asphalt of our drive way with a burn out. She was like yep, car's fixed.

One month later, I traded it in for a kid friendly SUV. She laid the "we have a new born daughter and she can't fit in the back seat, we have no room for stuff, " excuse. I fell for it and hate giving up my bird ever since.

[2002ssslp]

Enjoy the baby. Before you know it they will be off to college and you will wonder where the time went. After awhile, if you put some extra money aside you can get back into the game but for now it's SUV-CITY. I waited 10 years before I got my next toy. That's life.

on a different car I had a similar problem. It was like it was a ghost code. Popped up when ever it wanted too. Seemed it would only do it on a heavy load. When I pulled the plug I didn't see the hairline crack, but the second time I moved it back to the problem cylinder it feel apart. Replaced it and all was good. Sometimes the cracks just aren't obvious.


This was before there were forums like this online.

The worse trouble shooting experience I had was with my 96 Firebird. It would run rough, misfire, codes popped every week, either I would blow plugs, wires, or occasionally a coil pack over an 8 month period . Then I went to Korea for a yr and then got deployed to Iraq for another yr, so my wife just let it sit and she would run it at idle for 10 mins per week. During that time I research the hell out of this problem. I replaced everything coil packs, plugs wires. Then I came across a TB from GM that said to replace the plate that the coil sit on ever 70k miles due to it will cause shorts. I get back and do so, car ran like it return from the dead. I instantly could hear a see a difference. Wife asked me if all was good, I tore off a section of asphalt of our drive way with a burn out. She was like yep, car's fixed.

One month later, I traded it in for a kid friendly SUV. She laid the "we have a new born daughter and she can't fit in the back seat, we have no room for stuff, " excuse. I fell for it and hate giving up my bird ever since.

[98TransAmWs-6]

Another thing you could do is to check and or replace the #8 injector. I would do that after you check the coil,spark plug, and wire though. I had a misfire on #4 a while ago and it turned out to be the coil, spark plug,and injector....yea they all went out at once.

[SMWS6TA]

Enjoy the baby. Before you know it they will be off to college and you will wonder where the time went. After awhile, if you put some extra money aside you can get back into the game but for now it's SUV-CITY. I waited 10 years before I got my next toy. That's life.

This was almost 8 yrs ago. I did wait and save now I have my 98 T/A. It's my retirement gift to me from the time I served.

[Ain't Right]

I had same problem, tried everything, then it began on 7 5 and 3. Tried the best bosch plugs and wires, MSD wires E3 plugs...new coils...tjen the old man in serbice department at the dealer swore if I tried new factory plugs and wires at the same time, it would stop. Said if it didn't work he'd buy back the whole set himself. It worked....

[JayTA98]

ddo you have the heat shields on the wires? I dont have headers but the can cause arcing. I will do as everyone else suggested. swap wires, plugs, coils and lastly injector. Keep us posted.