pHEnomIC

iTrader: (14)

My car kept setting random cyl misfire codes randomly. I logged it and found out that solely at 1500 rpms, the car misfires like crazy. It seems to be mostly cyl #1, but others do it too. I am wondering if it really is cyl#1 or it is mis-calculating after the first miss.

It has a torquer v3 cam, full boltons, tr-6s (for spray, stock gap), bunch of misc stuff and supporting mods now. My tune seems to be phenomenal, my wideband reads fluctuations of 14.7 to slightly leaner at all low load stuff. ( i notice the advance goes up to about 40* when it misses, could i have too much advance?)

What is causing it to do this only at that rpm? I don't have any issues up higher or lower. I honestly don't feel any missing, my pcm just reports it.

I recently broke 3 valve springs (prc duals), and I reinstalled all springs to verify they are good.

stevied916

iTrader: (30)

switch coils around and check the resistance across the plug wires

00pooterSS

iTrader: (40)

also throw a plug in it for good measure, we have seen quite a few a/c plugs come through the shop here that are bad recently, new ones not old.

pHEnomIC

iTrader: (14)

What do you mean by plug?

Are you talking about spark plugs? As stated I am running ngk tr-6's, all plugs were checked to have the advertised gap (i forgot what it was exactly).

00pooterSS

iTrader: (40)

Yes spark plugs, sorry. And what you stated or the gap does not matter, as I stated I have had quite a few spark plugs come through the shop bad out of the box. Put in a new one and just try it.

Shawn MacAnanny

iTrader: (12)

Ya know i thought i noticed a lower rpm misfire when i switched out the plugs this last time for Tr6s. I wasnt sure though as i had just fired the engine for the first time and assumed it was just the carb still not being tuned right or broken in all the way. I'm going to throw a set of TR55s in there and see if it helps.

Swap a plug or two out jon, see if helps. I'm going to pull all mine tomorrow and look at them after having read this. i couldnt possibly see anything wrong with my ignition system as its all new plugs, wires, coils are used but are 01+ truck coils. I but he's right it's a Tr6 plug since i have the same problem. The car runs perfect above 2k rpm.

00pooterSS

iTrader: (40)

It shouldnt be that they are colder causing it, but more that maybe there is a faulty plug, seen quite a few AC Delco plugs come through recently bad right out of the box, a few the porcelain was loose, a few they were just bad, high resistance and not sparking from the tip, actually the spark was coming out of the porcelain.

pHEnomIC

iTrader: (14)

Ok i switched the plugs, wires, and coils on #1 and #3 each individually and nothing fixed the problem. So i think ignition is ruled out.

I guess next steps would be swap an injector, check under valve covers, pull some timing, try richening it a bit.

00pooterSS

iTrader: (40)

did you switch the spark plug wire too?

but yeah sounds like you know what to do next, sucks.

pHEnomIC

iTrader: (14)

Ok so Ive ran through all of this individually and can't find any problems:
Swapped spark plugs, swapped wires, swapped coils, swapped injectors, checked valve springs, etc, checked pushrods, retorqued rockers.

So I am still getting this misfire so as far as im concerned, Ive checked everything externally. IS there anything else to try? I am gonna try richening it up a bit, but that's about all I can think of.

Shawn MacAnanny

iTrader: (12)

Maybe it's because your gay? Nah back some timing off and see if that helps at part throttle. Ive been playing with my timing and fuel alot and gotten rid of nearly all of my mid rpm stumbles and missfires.