Number 4 cylinder misfire

[gchans007]

I have a misfire code on number four cylinder and a check engine light. I have looked over the posts and started to eliminate problems. I'm pissed that I let her buy it, but now I need get this running and smoged.


my niece just bought a used 1998 with the 3.8 V 6 (not supercharged). I ...
Replaced new plugs and wires. Delco
checked fuses
Checked for spark
Switched the coil packs.
Switched fuel injectors
good compression
no change

the code reader is showing 160+ misfires on number four only. all others 0 misfires.


because of antifreeze in the number 4 cylinder and it was overheating...
i also replaced the lower intake manifolds. While there I did see some small corrosion on the manifold from the antifreeze. I did not think it was significant.


still have a number four misfire. I Still can't smog it.

i saw someone say to check for wiring problems. Time for a specialist???

thanks for your thoughts.
greg

 

[Max Cook]

maybe the ICM? Try cleaning it up and putting it back in or swapping it (preferibly from a working gp as a test or a junkyard).

 

[locuno1]

if you figure out what's causing it let me know lol i've been dealing with a misfire/hesitation for a while now and i've switched coil packs, plugs, wires, icm but my misfire comes and goes.

 

[Max Cook]

I mean its apparently possible to have a chipped piston and still read good compression. You could get a borescope to check them out (hopefully find a place that rents them). On an NA car its not probably all that likely though.

 

[genki]

borescope is around $20 on eBay, from China or such. If you have a laptop with USB, try that. Make sure it's small enough to fit through the hole, most are 10mm or smaller.