Beating my head against the wall. Sbc random missfire

[pontiacgp]

what distributor are you using and have you checked the pick up coil and the star wheel on the shaft?

 

[crucial118]

I was talking with my dad and he seemed to think u could have a bad valve guide. Running e85 it washes the oil off the valve stem as it come through the intake and out the exhaust ( obviously not as much on the exhaust side to to burnt fuel) but if the valve isnt sitting on the seat correctly u would be losing compression. pressurized the cylinder with air and listen to where its going. could do a compression test as well

That's what happened to me. I had a misfire off idle in DRIVE to about 1500rpm. Couldn't find out what it was. I replaced everything electrical. Finally I put a compression test/leakdown test on it and there was no compression in #1 and #7. Exhaust valve leaks. Do a compression test before you spend too much on unnecessary parts.

 

[pontiacgp]

have you removed the plug so see if it's wet with fuel right after you have run the engine, if it is it's an ignition problem

 

[Stealth]

I did a leak down. It was at 5%

 

[pontiacgp]

did you do the test when the engine was warm or cold?

 

[Stealth]

Warm, my philosophy was that was when it started miss firing

 

[pontiacgp]

there is no problem with 5%

 

[Doober]

5% is actually pretty good, I believe up to 15% is reasonable?

My personal experience was plugs on the 383... had a usually minor misfire between 1800-2100rpm, turns out the plugs were causing it.

I didn't notice if you had... did you check that specific plug wire?

I've heard the term MSD:May Suddenly Die

 

[Stealth]

It was the damn carb. Ordering a bigs carb this winter..

 

[pontiacgp]

if it's only #2 cylinder misfiring I don't understand how a carb could cause that issue