misfire

[FUPA]

i changed my spark plugs and wires two months ago and it was working fine two months, but now it is misfiring again. Ummm, what should I do? Should I take em out and put them back in? Should I check to see if the boots are on there good and tight? I gapped them correctly, I made sure everything was good and tight and it was for two months. Has this happened to anyone here before?

[BLLDOGG]

No, we never get misfires.... [img]tongue.gif[/img]

pull the plugs and check their condition. then check if they are even firing. have you gotten any codes?

[Red]

might check the wires first before bothering disconnecting everything, possibly just meltd thru somewhere. Then check all else.

[FUPA]

no codes, and the wires were brand new two months ago.

And I forgot... how do you check to see if they are firing? Do I have someone crank it while I hold the plug by the boot and check for an arc?

[4thgenowner]

Stick your finger in the boots and have someone crank it. :D

[BLLDOGG]

just cause they arw 2 months old doesnt mean they cant be damaged by heat or just a defect.

you test it with a plug wire tester. its just a little tool that has a plug on it and you attach the the wire to that and clip it down. crank it and look for spark. never hold it cause you'll get shocked.

[geocor]

You can lift the car & spray water on the plug end of the wires ,this is what I did to find a bad wire that arced.This is what it sounds like 2 me.I had less than 1 year old MSD's & no.6 was bad.A real good scanner will find an intermitantant missfire too.I'm not talking about just an Autozone type code reader but one that does real time diagnosics,like a Snap-on,or OTC,& a higher priced AutoX Ray unit.

[FUPA]

This morning I wiggled the plugs in really well and pushed down really hard on the wires. No misfires from my girlfriend's house to my house, but I expect them again. It usually doesn't happen unless I am giving it a lot of gas- then it starts misfiring. So what does it mean if my misfire isn't constant? It must mean I suck at changing my spark plug or something.

[Marty85]

Ive seen this twice before with 3.8 f-bodys. First was water dripping down from cowl corroding the terminals from the ICM to the coil. Second was just simply a bad coil that had too much resistance in the primary and couldnt produce enough energy to jump the plug gap under large loads which require more spark energy. Both would only miss if you brake torqued them to about 1500 rpm's. So I would check for corroded terminals. Or it could simply be a bad coil pack.

[FUPA]

Originally posted by Marty85:
Ive seen this twice before with 3.8 f-bodys. First was water dripping down from cowl corroding the terminals from the ICM to the coil. Second was just simply a bad coil that had too much resistance in the primary and couldnt produce enough energy to jump the plug gap under large loads which require more spark energy. Both would only miss if you brake torqued them to about 1500 rpm's. So I would check for corroded terminals. Or it could simply be a bad coil pack.

That sounds very accurate. If the rpms get past like 2K it starts to misfire. If I drive it like a normal person it works fine. Since I am almost positive i gapped them correctly and inserted them right, you are saying it is most likely the terminals? So I should go buy a wire brush and check those first?

[FUPA]

I just brushed off the terminals pretty good and it is still misfiring. About how much would a new coil pack run me? I appreciate all the help y'all.

[Jayjay269]

I bet you need to get a new Coil pack. This is pretty typical of the 3800. Souldn't cost you a whole heck of alot, but it wont be below $120 installed.

[FUPA]

You guys are awesome. New coil packs fixed my problem. I hope you all are aware of how much money you save people. If you are ever in Clemson, I'll buy you a beer. [img]graemlins/rock.gif[/img]