Thread: New HEAD GASKET/PLUGS/WIRES/COIL/INJECTOR . Why is it MISFIRING ??!!!

2000 3.8 GTP, just wanted to do some work to the top end of the motor so it got NEW : Head Gasket, Upper and lower intake gaskets, Plugs and wires (Autolite), coil pack. When I first put it back together it was first showing multiple misfire code, then that one went away when engine warmed up and it threw "Misfire on Cylinder 6". Alright, so I figured only thing I didn't replace was the injectors, so I SWAPPED injectors between cylinder 1 and 6. I put it back together and at first start it showed again multiple misfire, it went off and then it threw MISFIRE #1(And lean on bank 1). Ok, I was POSITIVE injector was bad because the code just went from misfire #6 to misfire #1 now. So, I replace the injector, AND the coil pack for cylinder #1. Code is still on. After all, new head gasket, new plugs and wires, new coil, new injector, why in the world is it misfiring on one cylinder? (Wires are to each correct cylinder from coils so no issue there). Thanks a lot guys

Originally Posted by Fivefingerdeathpunch

Maybe the ICM died.

Check how strong the arc is between the 2 points on the coil pack, do it for all and see if there is a difference.

Thanks for the advice, I'll do that tomorrow, didn't think about it.

Originally Posted by Fivefingerdeathpunch

Maybe the ICM died.

Check how strong the arc is between the 2 points on the coil pack, do it for all and see if there is a difference.

Wouldn't it throw a code for a bad ICM ?

Originally Posted by Fivefingerdeathpunch

Nope.

There is no codes related to a ICM, you'll only see misfires or the car just wont start at all because there will be no spark to any coil/plug.

Wow, good to know. Thanks much

Originally Posted by Ginseng

maby you cracked the plugs. Try swapping them around, cyl 6 is notorious for it

I may end up going with ac Delco instead, I didn't gap the autolite plugs that I installed, just installed them the way they came out of the box, could that be a problem too ?

Update : I replaced the Autolites with AC Delco and problem still occurs , misfire on %1. Replaced (from a different gtp I got) the ICM, and problem still exist. At this point issue isn't plugs, wires, injector, head gasket or coil. Damn it !!

Coil was replaced, I also did change the wire to see if the misfire goes to a different cylinder but it stayed on number 1. This is driving me crazy there's nothing I haven't changed I guess ..

Start at the top, compression test.

Thank you guys for all the advice. Problem ended up being the lower intake manifold gasket. What's the problem ? Well, when you buy a stupid aftermarket head gasket set for 65 bucks off ebay, you end up getting an intake gasket that is NOT SHAPED at all around the injectors holes to allow injectors to sit in correctly. Its a straight line that covers almost quarter of that hole so you'd think injectors are seated well but they're not, and therefore I had a problem. I had to cut the gasket around the injectors holes and reinstall everything, it is fine now. Again, Thanks a lot.

Originally Posted by REDCOMPG

Future word of advice is just to get the parts from the past store and you'll probably will be spending the same amount. eBay isn't something that I would trust when it comes to engine parts.

I learned that first hand now, however, I will be posting a thread about a part that advance auto parts sells and causes a lot of people so much work when the apart is actually bad! It's the coolant temp sensor.

Originally Posted by REDCOMPG

You referring to the sensor underneath the t stat housing? $15 part easy to change....works fine.

Sounds like he's referring to the low coolant level sensor to me.
And most of the time it isn't bad but just needs cleaning.