misfire on cylinder 3

[fordfan86]

ok so obviously due to the title of this thread my 98 4.0 v6 SOHC has a misfire on cylinder3. i have changed the plug the wire the coil pack and both the gasket on the upper plenum and the fuel rail and i even switched the number 3 injector with the number 2 to see if it changed anything and what do you know it didnt. so now i have no idea where to go from here. im guessing either pushrod or valve issues maybe? i have also sprayed around the vacuum lines with starting fluid to see if anything happened but again i got nothing. any help would be awesome, thanks guys.

 

[adsm08]

Check the injector pluse with a test light. See if it flashes while cranking when pluged in in place of the injector.

If that is a no go, then do a compression test.

I'll be in town tomorrow if you want me to stop in.

 

[fordfan86]

will do thanks for the info.

 

[Duane867]

Have you tested the ICM ?

 

[fordfan86]

ICM?

btw adsm, what does it mean if it doesnt light up and what do i have to change if it isnt lighting up?

 

[adsm08]

Have you tested the ICM ?

It's a 98. The PCM performs that function. Given the parts changed already if it was a coil driver issue 4 would be missing too.

ICM?

Ignition control module. Your truck doesn't have one in the sense that Duane is thinking of. It's become a function of the engine computer.

btw adsm, what does it mean if it doesnt light up and what do i have to change if it isnt lighting up?

If it's not lighting up at all you probably have a broken wire. The other alternative is the PCM is shot. Break out the volt meter. Check for power on the colored wire of the plug. Then check continuity to the PCM plug on the other wire.

Seriously, I'll be in town today, late morning to early afternoon. I can stop in and help you check over it. I'll send a PM with more info.

 

[Duane867]

It's a 98. The PCM performs that function. Given the parts changed already if it was a coil driver issue 4 would be missing too.

Got'cha.

 

[fordfan86]

checked injector pulse and its good didnt get a chance to check the pcm. i will do that tomorrow. if all else fails i have a good friend is is a real live mech and he always tell me whats wrong so i can fix it myself and he doesnt charge me so if i cant figure it out i will just bring it to him.

 

[Duane867]

Yeh cuz were all robots n stuff.

 

[fordfan86]

i didnt mean that you guys arent mechs or don't know what your talking about. i meant that i am not and so i would rather take it to him than miss something simple and keep beating my head against the wall. sorry if that was offensive to you duane it wasnt my intention.

 

[Duane867]

No you weren't at all, that was me just being me and joking around

 

[adsm08]

Well if injector pulse is good then that rules out a number of things including the PCM.

 

[fordfan86]

No you weren't at all, that was me just being me and joking around

oh ok its so hard to tell sometimes, still waiting for that sarcastic font to come out so its easier to tell.

adsm, if its not that then what next? i havent got a chance to test the compression yet so i will start there if you think thats a good one to check.

 

[adsm08]

If you have fuel pulse and you have spark, there isn't anything else to look at.

 

[Andy D]

burnt exhaust valve?