Thread: Cylinder 3 misfire Tried everything I can think of

All I know about it is

It's not an injector(swapped)
It's not a chipped cylinder(compression test)
it's not a plug(swapped and gauge checked 3 times)
it's not a wire(swapped)
it's not a coil(swapped)
It's not a ICM(swapped)
also seafoamed
and cleaned MAF

problem is confined to cylinder 3 regardless of components

the problem is intermittent at best nowadays seemed to get alot better after switching to 93 octane

could bad gas alone cause a misfire?

problem occurred after doing headers and plugs

could a bad exhaust leak cause a misfire?

edited post as problem became intermittent and than non existent and than intermittent and than gone again

yeah well I have adjusted them several times now swapping from 5-3 and than swapping wire 3 completely

it was pretty obvious when I had them wired wrong on one occasion as soon as it fired up I could tell it was a consistent misfire

this really only happens towards the higher RPMs and idle is completely normal around 700ish

How about checkn some of the grounds? theres 1 below the icm n the battery 1s.... clean them?

Y u no do compression test?

Originally Posted by blueguy91

Y u no do compression test?

Originally Posted by Beelzeboul

It's not a chipped cylinder(compression test)

didn't he?

Actually.

Don't mind my post.

Carry on.

Any ticking noises?

A sticky valve guide may cause a miss only when the car is running.
It could also be a lifter not pumping up.

never heard of a bad ground causing a misfire even than it seems a little odd that it would be the same cylinder every time and not shorting anything else out but ill go out and check over them Im usually good about all my electronics though.

The lifters I will have to check can I just remove the valve cover and fire it to watch for which one is skipping?
saw a video on a guy doing this wasn't sure on how safe that would be

Safety isn't an issue, just don't run it for a long period of time because it will get MESSY!!! You're squirting oil all over and might catch fire on the headers. Slim but possible. I've adjusted rockers this way on several older V8's I've built. Just clean your header good afterwards and everything else.

Did you switch coil packs around? I know you switched wires. Don't know about the ICM. My experience is they either work or don't, but could be a short in your ICM. Would a crack between your exhaust and intake valves show up on a compression check? Crack might show up more under more heat and that being a middle cyn. it gets hotter then the outer two.

Originally Posted by dbextreme

Safety isn't an issue, just don't run it for a long period of time because it will get MESSY!!! You're squirting oil all over and might catch fire on the headers. Slim but possible. I've adjusted rockers this way on several older V8's I've built. Just clean your header good afterwards and everything else.

Did you switch coil packs around? I know you switched wires. Don't know about the ICM. My experience is they either work or don't, but could be a short in your ICM. Would a crack between your exhaust and intake valves show up on a compression check? Crack might show up more under more heat and that being a middle cyn. it gets hotter then the outer two.

yeah thats what I was told about the cylinder 3 and 5 tend to be the leanest and misfire will occur in those first or chipped pistons or commonly 3

dont think exhaust leaks would show up in compression test and yeah I had swapped coils and ICM both leaving me with the same intermittent misfire
it actually got more dominant after swapping icm and than even out after a pcm relearn all my ftlts and vac levels seem appropriate though even at high speeds not sure if the vac would be affected by the exhaust leak either

gonna check the valves tomorrow than just worried its not going to act up for me unless I throttle the hell out of it at the moment the problem only occurs on boost

*smacks forehead* I read that, I just got to thinking and forgot you did all that already.. LOL Sorry!!

np I've been smacking my forehead for about a month now what bothers me is how touchy it is things will run better than fine for a day than bog for an hour than run fine again really weird I have a video of the symptom in my photo bucket via my profile showing it at its absolute worst

Did you gap your plugs right?

Also have you taken the valve covers off to check for a broken spring or bent pushrod?

yeah 3 times the problem seemed more dominant at the 58 mark I read to gap them at initially so I took them all out and re gapped down to 50 but while worrying about the chipped cylinder I checked it again for damage and made sure it was still at 50 and another time when compression test was done ad even swapped plugs one more time to be sure

should they be gapped below 50? tr105s i believe (went with the one range cooler ngk)

ps your rims are hawt swiggle

Thanks

What are your mods? If your stock try the stock sized plugs.

What kinda plug wires u runnin?

stock wires mods are headers intake and tstat. kinda presented itself this morning rather ugly first when i started car the pcm had reset suggesting my battery died over night

looked around under hood and it looks like the sd hood cowls drip water right on top of my coil pack is this something I should be concerned about.

I'll probably pick up a new set of wires today and hope it helps also found out I needed a new SC belt tension er so gonna be heading to the jy today to grab one after my doctors visit(thanx for the info about cylinder misfiring with swapped wires I can put something easy back of the list of possible culprits)

the fact that the pcm went dead is kinda what threw me this morning leading me to believe it might be an electrical problem I took my battery halo and amp grounds off cleaned them all up and reinstalled

gonna have to check valves as well afterwards is it just the couple bolts on valve cover I need to remove and not a gasket or anything ill have to replace and should pick up before attempting?

will have a video up by tonight of my valves in motion

but I was getting several backfires throughout the course of chasing my dogs down this morning along with stuttering I'm leaning towards wires or something as far as my fire components at fault