MBredestege

Here’s what I’m dealing with guys.

I have a 2000 Cherokee Sport with only 52,000 miles on it. It has been garage kept and maintained by the previous owner (father-in-law) who got it with 25,000 on it in 2003.

I had a coolant system issue about 2 months ago. I was getting no heat this winter (sucks bad in the Ohio valley not to have heat in the winter) so I did a chemical flush on the cooling system and it was a MESS. After assembly all was well and I got my heat back so the heater core survived. I also had a pinhole leak in the radiator which resulted in a mild overheat last summer. (Red flag number 1).

While driving one evening two weeks ago it seemed to be running just a little off and it then threw a check engine light. I was about 15 miles from home so I continued on my way not to concerned about it.
A few minutes later it the check engine light started flashing about every 5 minutes and it developed an bad miss. I got it home and decided I would deal with it in the morning. The next day it started up just fine and seemed to be running fine. The check engine light was out so I drove it out to a friend’s house and after about 5 miles the issue returned BAD, I barely got it home the way it was running.

This time the check engine light stayed on so I pulled the code and it reported a misfire on cylinder 5. I figured it was a spark issue so I pulled the coil pack and changed the plugs out (Champion Copper Plus) and put new boots on the coil pack. Boots are cheap and faulty boot can rob spark so what the hell.

After reassembly it still had a horrible miss so I started digging deeper.

I pulled the plugs again and after less than a mile the number 5 plug was already collecting black soot. So I figured it may be an injector issue and started looking that way.

Then I pulled the dipstick.

Coolant 8 inches up the stick. Yep, the dreaded 0331 head issue. No coolant or any smoke at all out the exhaust, just coolant in the oil. At the last oil change about 1,000 miles back I noticed the oil was high, about one quart and had an odd color to it. I had added a half quart of Rizlone due to a little sludge building up on the oil filer cap (red flag #2) so I just figured I had topped it off to high at the last change and got side tracked and didn’t think about it again till this point.

I’m figuring the mild overheat cracked the head but the leak was very small/slow due to the heavy corrosion in the coolant system so it wasn’t discovered right away. After the coolant system flush I figure the leak accelerated.
At this point I couldn’t diagnose the misfire till I corrected the cracked head. It may be related, maybe not.

Got a brand new head from Clear Water Cylinder Head (really nice workmanship on the head, top notch machining work. Highly recommend their replacement heads)
Pulled the old head off, no coolant in the cylinders, gasket was fully intact and all cylinders and valves looked excellent except the number 5 intake valve was very dark, the cylinder walls still had the crosshatching from the factory hone on them.
Nine quarts of fluid came out of the oil pan so I had about three quarts of coolant in my oil slowly added over the last 4 months/1000 miles.

New head
New head bolts
All high quality FelPro gaskets
New heater hoses
New radiator hoses
New radiator
New PCV valve
New crank case vent
Fresh coolant, oil and filter, air filter

Cleaned and reassembled it, did a reset since it had been sitting for two weeks with the battery off and then fired it up.

It ran perfect for about 15 seconds then the miss returned. Drove it around the block and got a check engine light, pulled the code,

P0205 Injector #5 Control Circuit Injector #5 output driver stage does not respond properly to the control signal.

I decided a set of injectors wouldn’t hurt so I contacted jhc7399 and lucked out because he lives locally. He set me up with a set of 784/4 port injectors over the weekend, he sells an excellent multi-port injector if you need a set.

New injectors in yesterday, reset PCM (Pos and Neg cable together 30 seconds, reconnect, key on, headlights on then off, key off.

Started it, ran good for 10 seconds then started missing.

Started digging again.

Noid test all injector plugs – flashing light at all 6 when running.
Pulled the coil pack, plugged it in and cranked it over spark at all 6 but cannot tell if they were all a strong spark.
Continuity checked the injector wiring harness back to the PCM, all checked good.
Compression checked cylinders, 150 on all 6.
Oil pressure at 45 on cold start drops to 40 at idle when warm. Been that way since the day I got it so I’m hopeful the rod and main bearings are solid.
Vacuum check at 13 inches at idle on the manifold
Pulled the plugs (will try to attach a photo) #5 for only having 30 minutes run time on it looks very dark. #2, #4 and #6 are a little dark. #1 and #3 look like they just cam out of the box.

Bolt it all back together.

At an Idle it has a miss,
If I rev it hard it runs good for a few seconds after it spins back down, maybe for 3-5 seconds then goes back to the hard miss.
Under load it feels like 4 cylinders are down, it just goes to hell.
If I hold it at 1500-2000 RPM in park it feels smooth as glass, seems miss free.
At an idle it sounds good mechanically but has a miss. Under load or above 2000 RPM the miss is horrible and the engine sounds horrible, bad knocking and bucking.

Where the heck do I go next? Crank shaft sensor? PCM?

Could it be air flow sensors? Throttle position sensor?

I’m at a loss…

My crank shaft sensor is not as hard to get to as many have said. I can reach both bolts from the top and can reach it. The plug however is only accessible from the bottom but I can get it.
My PCM in not on the passengers side firewall like in many posts, mine is on the fender wall behind the air box so it is easy to access too.

Any ideas would be greatly appreciated. I DO NOT want to take it to the garage as I hate to admit defeat.

Sorry for the long post but I wanted those who might have a solution to have as much info as possible.

Thanks,
Michael