02 Wrangler misfires

[leek]

ok.....so 02 4.0 200k auto wrangler had a code come up jeep wasn't running warm enough so changed thermostat cleared code everything was fine, couple days later I get cel p0300 and its for cylinder 1 and 3 idle is kind of crappy if you try and drive it wants to die. I've read a lot of threads so I went balls deep and replaced some things, spark plugs AP985 gapped to .35 didn't change the outcome, replaced coil rail to $135 dollar Oreilly's sold me, changed crank position sensor none which have changed a thing. What now? could it be from changing thermostat?? all ran great until that, do I bite the bullet and send it to a mechanic? any help would be greatly appreciated I've tried resolving from other threads first.

 

[Cooper Smith]

ok.....so 02 4.0 200k auto wrangler had a code come up jeep wasn't running warm enough so changed thermostat cleared code everything was fine, couple days later I get cel p0300 and its for cylinder 1 and 3 idle is kind of crappy if you try and drive it wants to die. I've read a lot of threads so I went balls deep and replaced some things, spark plugs AP985 gapped to .35 didn't change the outcome, replaced coil rail to $135 dollar Oreilly's sold me, changed crank position sensor none which have changed a thing. What now? could it be from changing thermostat?? all ran great until that, do I bite the bullet and send it to a mechanic? any help would be greatly appreciated I've tried resolving from other threads first.

p0300 is a random misfire. p0301 and p0303 would be the cylinder specific codes. The thermostat is most likely coincidental. That's just water jackets and bleeding the system for the most part. My truck has a ground on the thermostat stud, do you have a ground there? My Jeep was a 2.4 so I don't know the 4.0.

Fuel pressure test possible?

 

[Chris]

Find someone with a scan tool that does live data scanning. You can tell a lot about what's going on when you watch the engine running in real time on a live data scanner.

Could also potentially be a short circuit in the wiring somewhere as well.

 

[macleanflood]

A $30 Bluetooth dongle and Torque Lite will read live ODB data.

If you want to keep firing the parts canon my vote would be the crank position sensor.

-Mac

 

[Brimstone]

I would not have recommended the AP985 (single platinum) plugs, I would have gone with APP985 (double platinum), actually personally I would have just gone to iridium plugs. Does not explain why the issue began or why replacing the plugs did not correct it, just personal recommendation.

Did you damage the connector or wiring for the coolant temp sensor?