WaY_WeiRd

Glad I didn't spend a fortune on a new friggin coil pack.

Per mechanics diag, I was led to believe my coil pack was bad. I had a misfire on six.
Here is my original post: https://www.cherokeeforum.com/f2/200...ucking-160315/

He charged me like $80 to swap the injectors, test fuel pressure, check to see if it was bad gas, etc. Said all it could possibly be is s bad coil pack. So, i tracked down a used one, even though I felt like that was probably BS.

Had my fiance change out the coil pack in the lot, before leaving the shop. Was running alright. Got half way home... Started the same crap all over again.

Had AZ scan it. Misfire on six again. WTH.

Any ideas? Plugs were changed when motor was rebuilt in October. If it's plugs, what would cause those to go bad so soon after an entire motor rebuild?

tjwalker

You gotta get a new plug in there just to make sure it isn't the problem. Probably not it, but it would be sad to chase your tail for a $2.00 plug. BTW, what plugs are you running? There have been a few 4.0 engines that have had misfires with plugs like E3, Bosch, etc. I recommend NGK copper plugs gapped to .035 for the 00-01 ignition system.

After that, I would run a compression test on all cylinders. See where #6 is compared to the others. If low, add a tablespoon of oil to the cylinder and re-run the test to see if compression improves.

I know you rebuilt the motor. You still must consider the possibility of an internal problem.

WaY_WeiRd

Mechanic ran a compression test. Results of that were fine.

tjwalker

Swap out the spark plug. You could have something simple like a cracked insulator on a spark plug. 5 minute job and is the first thing I would do if I was working on it.

Not saying that is what it is. I am saying you must rule it in or out.

98_XJ Sport

Got a misfire on one of my cylinders a while back, took out the plug and there was some gunk covering the electrode. Wouldn't hurt to check it.

Jamie57

sub'd as I'm having the same damn problem. P0306 right?

Changed coil pack
changed plugs
changed injectors
Changed O2 sensors
Did compression test.
Going to change Idle motor.
Going to change fuel pump
Don't have a damn clue what else I can change to have 1, just 1 f'n plug misfire. Will take off valve cover if the GD global warming the chicken littles have been screaming about ever returns, and check valve train.

WaY_WeiRd

Yeah. Same code. Only code it's throwing too.

WaY_WeiRd

Just had a thought. Could this have anything to do with my weird one time voltage problem from a couple weeks ago? It dropped randomly and came back up, but didn't stall... And the problem never returned.

Also, my battery was having a hard time holding Charge during diagnostics today, apparently. Being z cheap quick fix battery, I'm not surprised... However, could they all be connected?

JJCIII

Sounds unlikely they are connected. A sudden voltage drop isnt a battery issue unless there is a broken cell. Probably a charging circuit issue. But dont rule out battery and ground cables being loose or corroded as this can cause that issue. Start with that then a battery. Start cheap. If recently read of people having misfires due to weak or broken valve springs. Youve ruled out some other suspect so its a thought.

WaY_WeiRd

Well, fiance got called into work and has all his tools with him in his semi.

Soooo, i can't check the plugs myself. Anyone in metro Detroit wanna come over and help?

Or, if i take it back to the shop, since they misdiagnosed, should i have to pay another diagnostic fee?

WaY_WeiRd

Officially Fed up. Called the shop back. Asked if he swapped plugs. Answer was yes. Problem did not follow the plug. Plugs looked fine. Ok, so i ask, what kind of plugs were put in it at the time of rebuild. Champion platinum plugs. I mentioned that I've heard of cherokees not liking platinum plugs. They should be copper plugs. Know it all says, well the platinum champions are the updated OEM plugs that should be in it. Probably a wiring problem. So, i ask, i suppose if i brought it back, I'd get charged another diagnostic fee? Well yeah.. Because we don't know if it's the used coil pack. Bull. It's misfiring on the same cylinder. Obviously it's not!

Kris smith

have you tryed to swap the coil with a known good coil pack and see of the miss follows the coil ? thats the best bet other than that i would be checking your wiring that leads from the ecu to that coil pack. if al that checks out it may be an ecu issue

Kevin108

I would reindex your camshaft position sensor. http://www.jeepforum.com/forum/f11/h...ensor-1145301/

CCKen

What were the exact compression test readings?

It seems some people really don't know how to perform a compression test properly, and they don't know what the Jeep FSM limits are (120 - 150 psi, with max variation between cylinders 30 psi).

A compression loss test should be done on that cylinder to see if the valves are okay. The person that rebuilt your engine may have buggered up one of the valves in #6, valve springs, or the rocker arms bridge when torquing them down. A visual check of the #6 rocker arms and springs should be conducted.

You can run a can of Mopar Cumbustion Chamber Cleaner through your engine to see if it cleans up any chrap under a valve. CCC is from the Dealer. Much better than that jesus juice Seafoam.

Go to a different mechanic than that 1st joker and have them do a compression test on all cylinders and a compression loss test on #6. If the new nose picker that will do these tests needs FSM info, let us know and we can post it here for you to print off and take with you. Just make sure the nose picker can read and understand the English language.

WaY_WeiRd

I have no idea what the readings actually were, other than that he said they were fine. I even had them pull a sample of gas and that looked fine.

I'm due to have a baby in two weeks. My shower is on Sunday. I have to work tomorrow. I have no idea what to do at this point. I'm BROKE.

Please... If anyone can help... If anyone knows of anyone who can come to my house and take a look at the damn Jeep, I'd appreciate it. I can't keep throwing money at TRYING to diagnose the problem, and the shop doesn't seem to understand that. I already paid almost $4,000 a few months ago to get it running again, and now this.