QueenCityCrawler

So i purchased a 2000 Cherokee Sport 4x4 all original with 130k miles not running. I later found the wiring harness that runs along the firewall was sagging and chafing against the fue rail, burning the ecu fuse. I separated and taped the wires that were partially cut. Before i found that problem, i replaced the following:

oem Crankshaft sensor
Battery
Oem ignition coil rail
Oem spark plugs (gapped)
Fuel relay
After​​​​​​ i got it running but had multiple codes i replaced the following:

Injectordy​​​​​​ne 4 hole injectors
Oem catalytic converter (was clogged)
New catback exhaust
Ran bg44k thriugh it
Ran cold compeession test, 1 and 6 were the strongest ones

Before it had 6 codes, now its down to two, misfire cylinder 1 and 6. I tested the wiring plugs with noid test lights, 1 and 6 are same as the rest, but injectors 1 and 6 are not spraying because engine doesnt bog down if you unplug either one.

Is it possible that i have to go back to the wiring and replace the sections that were partially cut? Any ideaa?

Thanks everyone!

extrashaky

You can't assume that. What if the plugs aren't sparking? Then it wouldn't matter if the injectors were spraying. Pulling the connectors off wouldn't make any difference.

The coil rail has three coils on it, each of which fires two cylinders. I could be mistaken, but I believe #1 and #6 are on the same coil. If that coil has gone bad, it might behave the way you have described. Do you have a friend with a coil rail motor who might let you borrow their rail for a few minutes to see if maybe yours has a bad coil on it? Or you can just order one.

If you still suspect the injectors, there's an easy test you didn't mention doing. Swap those injectors with cylinders 2 & 5 and see if the misfires move with the injectors. If they don't move, you know the injectors are working, and you have already verified with the noid light they're getting signal. At that point I would be looking at spark.

fb97xj1

QueenCityCrawler

Thanks for the reply, i didnt know 1 and 6 were together. I did replace the coil rail with a new oem one and refurbished injectors.

extrashaky

Sorry, I missed that. In that chafing you noted in the wiring harness, could there have been damage to the wires going to the coil? If I had wiring that was "partially cut," I would cut out the damaged portion of each wire and make a good splice. You can't be sure a damaged wire is conducting properly.

Did you verify you have good fuel pressure?

Did you replace the camshaft position sensor? You might remove it (two screws) and see what condition it's in, then try reindexing it. Instructions are here:

http://www.jeepforum.com/forum/f11/h...ensor-1145301/

There are also a couple of known issues with the valves and valve springs in the '00 and '01 that result in misfires. One problem is that carbon build up on the valves prevents them from rotating and fully closing. You may be able to remedy this with the old steam cleaning procedure of slowly pouring water into the throttle body while the engine is running. Or you can use Mopar Combustion Chamber Cleaner (part # 04318001AB) to do the same thing. There's a more involved TSB for valve rotation as well:

http://www.wjjeeps.com/tsb/tsb_wj_0900303.pdf

The valve springs on the '00 and '01 are also known to sometimes break. You might consider pulling the valve cover off and inspecting the springs for damage. This ended up being the source of my cylinder six misfire, although I'm running a more aggressive cam than stock that may have contributed to it.