2000 Corvette. Boltons, tune, full exhaust with high flow cats, truck coil packs.

So I started to get a misfire in cylinder one while driving several weeks back. No valve train noise. Car was running perfect up until that. Flashing P0301. Cylinder 1 misfire.

1. The car was also due for some new wires and plugs. So I replaced them with Granatelli's and E3 plugs. Changed oil too just cause. When I pulled cylinder 1 plug it was fouled out and darker than the other plugs so I figured I found my culprit. Also, car ran great after the change. I manually cleared the code with my scanner and for over 60-70 mi no code or misfire. Ran strong.

After about 60-70 mi the misfire for cylinder one came back

2. I removed cylinder 1 coil. Blew it out with compressed air double checked the wires and plugs. made sure everything was tight. Bolted it back on , and same thing. Car was good for about 60-70 miles. ran strong no miss.

After about 60-70 miles misfire in cylinder one came back.

3. So I purchased a new single truck coil. Cleaned air filters, cleaned MAF, and, cleaned the throttle body. This ran perfect no codes for probably over 100 mi..

LOL Then the misfire came back on cylinder 1 after 100 mi.

4. SO AT THIS POINT I'M LIKE ITS GOT TO BE THE INJECTOR. So I borrowed an injector from my Camaro (same exact Ls1 injector). Swapped it. Let it idle. ***AND FOR THE FIRST TIME WITHOUT ME MANUALLY CLEARING THE CODE WITH MY SCANNER IT CLEARED ITSELF. CAR RAN BETTER THAN EVER...

But guess what its back. Same thing after 70 or so miles cylinder 1 misfire flashing.

ANY suggestions or pointers??????

If it was a bent push rod or broken spring wouldn't the problem be constant???? It wouldn't go away and come back intermittently??????

Or if it were the fuel filter or fuel pump. Wouldn't it throw a Random cylinder misfire P0300?????? Not just always cylinder one. Same thing with the cats going bad. That wouldn't only cause a misfire in the same cylinder every time right????

Please help thanks!!!

 

nobody???? help lol

 

Do a compression and leak down test, that will tell you more about whats going on. Post up pictures of the plugs might help too.

 

You certainly have addressed the problem logically, or at least exactly as I would have.
My next step would also be a compression and leakdown test to rule out anything mechanical.
After that I would replace the PCM.

 

Thanks G8One2 & mrvedit.

Yeah that was going to be something I tried today. Yesterday I did some more
local stuff to the cylinder to try and see if I could at least change the miss to another cylinder.

5. Swapped plug to cylinder 3.... nothing
6. Swapped wire to cylinder 3....nothing
7.Swapped injector cylinder 3, thought maybe my used Camaro injector went bad too.... nothing

Since I did not have the tools to do a compression or leak down test I thought to just pop off the valve cover to humor myself and make sure it wasn't a spring or push rod even though I know it going away and coming back ruled that out in my mind.

So pulled the entire truck coil pack. Something caught my eye. one od the plastic clips you cant really see under the metal coil bracket wasn't really attached. nothing major it just holds the coil wire harness close to the bracket. The wires were taped and heat shielded there anyways. However they were toughing the hot valve covers...hmmmmmm. I also notice some cracked wires at the connectors exposing the smallest of copper wires at some of the connector on the harness. Not at the #1 cylinder coil but at 3 &5.

So I thought what the hell just throw the entire original corvette coilpack back on. Keep them in the trunk anyways. Misfire went away code cleared itself!!!!!!!!!!!!!
Beat on the car all last night. It didn't come back. So I'm hoping that the problem was a short or burnt wire in the Truck LS2 coil harness that is attached to the coil bracket. And every time I changed a plug, wire, injector, or connector it must moved the harness and kind of temp fixed or the short.

Going to go beat on the car now and hope it isn't just another 60-100 mile band aid.