Sexton

I have a 2000 Jeep Cherokee Limited and have a constant misfire on cylinder 1 and 6. The misfire is soo bad that I am not driving it due to lack of power, and I'd rather not do any un-necessary damage.

SHORT STORY:
I replaced a "replacement" motor with the original motor in my jeep. That was a little confusing, I pulled and rebuilt my original motor, and now put it back in my jeep. I installed the Cam position sensor 180 degrees out the first time and it would not start at all, so I uninstalled it and put it back in following the toothpick in the access hole with the motor in TDC on the compression stroke. Now the motor starts up with ease, but cylinder 1 and 6 are not firing. I have not pulled the codes yet because I haven't been able to drive it to the parts store. But I know it is cylinder 1 and 6 by pulling the fuel injector wires on each cylinder to see which cylinders changed the way the motor was running.

LONG STORY:
I blew my original motor due to the head being cracked. I bought it from a guy who put that head sealer crap in it which made the jeep run awesome for 3,000 miles and when I got on a long stretch of interstate with no exits, the temp started rising but never went over 220 (or so the temp gauge says). So I continued to the nearest exit, and by the time I got there the motor was knocking and clanking around as if it was tearing itself apart! As soon as I brought the jeep to a stop, it shut itself down and started spewing smoke everywhere. Opened the hood to find blown head gasket and oil all over. Found out it blew a hole in a piston and head was cracked in 3 places. 0331 head FML

Pulled motor and put in replacement motor from a 99 cherokee that had a slight tick in it. Slight tick turned into wrist pin noise, and eventually grew to a loud knock. I put this motor in with the coil pack basically hanging on the cylinder head, and NEVER had an issue with ANY misfire the entire time it was in the jeep which was for about 10k miles.

Replaced the original motor in the jeep, with the 99 cylinder head. Now a misfire.

Will be replacing the spark plugs today, maybe this will yield results. But if not, what else should I be looking for? I will see if I have a compression tester at the house somewhere to test for compression, but I don't see how the compression would be lost, never had an issue with cylinder 1 or 6 on either of the motors. I've read that one of the coils runs cylinder 1 and 6 on a loop, so I could believe the coil to be suspect, but it was working perfectly fine 4 days ago when I pulled it. And when I pulled the spark plugs off cylinder 1 and 6 looked dry where as cylinder 5 still looked wet, could that be any indication of the fuel being shutoff to those cylinders by the computer for some reason?

And this problem is constant, I started it after the install of the motor and it was misfiring immediately and does not go away with higher RPMs, load/no load, or at operating temperature.

Donnie_K

mine did that 1 and 6 misfire when I changed my cam. Turned out I had the distributor a tooth off, apparently you can't use the alignment holes, they're wrong. Since yours has the coil packs, did you try switching the two misfiring coils to different cylinders to see if the misfire moves with them?

Sexton

The 2000 4.0 motor has a coil rail, so you can't switch coils.

I did however swap out the cylinder 5 and 6 spark plugs to see if the miss followed, but it stayed on 6. I pulled cylinder 1 plug and did the same thing with the same results.

I was wondering if maybe I had the CPS a tooth off, maybe somebody can chime in here and explain this a little further.

I could not get the oil pump slot to line up correctly, so I spun it until the CPS fell all the way down flush with the block. At that point, I made sure that the access hole on the side of the CPS lined up with the little hole on the inside of the sensor and bolted it up. So would it have really mattered what tooth the sensor was on, as long as when the motor is at TDC the two holes lined up at the sensor?

Theoretically meaning that I could install the sensor facing whatever direction (Or on any tooth that I wanted) as long as when cylinder 1 is at TDC on the compression stroke, those two holes lined up.


At the same time, when I was rotating the engine to TDC, I may have been 1/16 - 1/32 of an inch ( very little ) past the 0- mark on the crankshaft pulley gauge. Would that small oversight be causing this issue? I figured I worked on chevy and they usually have a small amount of tolerance there so I just went with it, if you guys think this could be the issue, I would gladly go in there and redo this to see if it will solve the problem as it would only take 15-30 minutes to get this done.

Donnie_K

sounds like that's what ya gotta do. If it's anything like the distributor was with those holes though, lol. Had me down for a week cuz I kept using those holes to find out they just weren't right.

Sexton

Well, I've read that your not supposed to adjust timing by spinning the CPS sensor around inside the hole like you would the older vehicles, but after I noticed the misfire, i figured WTH I'll try it, I loosened the bolt and spun it a little one way and the engine studdered but no change in the misfire, spun it the other way slightly and it just shut down.

So I don't know if they are way off, but I figured if it was only slightly out of alignment, that I could spin the CPS a little and get it to correct itself. Unfortunately, no such luck, and I'm going on 5 days with the Jeep down having had the jeep on the road last thursday and starting the motor pull on Friday.

CCKen

Here's the instructions from the 2000 FSM for instllation of the oil pump drive and sensor. Note that the instructions calls for using DRB Scan Tool (dealer). Hope this gives you some insight to resolving your problem.

INSTALLATION—OIL PUMP DRIVE AND SENSOR
(1) Clean oil pump drive mounting hole area of engine block.
(2) Install new oil pump drive-to-engine block gasket.
(3) Temporarily install a toothpick or similar tool through access hole at side of oil pump drive housing. Align toothpick into mating hole on pulse ring.
(4) Install oil pump drive into engine while aligning into slot on oil pump. Rotate oil pump drive back to its original position and install hold-down clamp and bolt. Finger tighten bolt. Do not do a final tightening of bolt at this time.
(5) If engine crankshaft or camshaft has been rotated, such as during engine tear-down, CMP sensor relationship must be reestablished.
(a) Remove ignition coil rail assembly. Refer to Ignition Coil Removal/Installation.
(b) Remove cylinder number 1 spark plug.
(c) Hold a finger over the open spark plug hole. Rotate engine at vibration dampener bolt until
compression (pressure) is felt.
(d) Slowly continue to rotate engine. Do this until timing index mark on vibration damper pulley
aligns with top dead center (TDC) mark (0 degree) on timing degree scale (Fig. 31). Always
rotate engine in direction of normal rotation. Do not rotate engine backward to align timing marks.
(e) Install oil pump drive into engine while aligning into slot on oil pump. If pump drive will
not drop down flush to engine block, the oil pump slot is not aligned. Remove oil pump drive and
align slot in oil pump to shaft at bottom of drive. Install into engine. Rotate oil pump drive back to its original position and install hold-down clamp and bolt. Finger tighten bolt. Do not do a final
tightening of bolt at this time.
(f) Remove toothpick from housing.
(6) Install sensor to oil pump drive. After installation, the CMP sensor should face rear of engine 0°.
(7) Install 2 sensor mounting bolts and tighten to 2 N·m (15 in. lbs.) torque.
(8) Connect electrical connector to CMP sensor.
(9) If removed, install spark plug and ignition coil rail.
To verify correct rotational position of oil pump
drive, the DRB scan tool must be used.
WARNING: WHEN PERFORMING THE FOLLOWING
TEST, THE ENGINE WILL BE RUNNING. BE CAREFUL
NOT TO STAND IN LINE WITH THE FAN
BLADES OR FAN BELT. DO NOT WEAR LOOSE
CLOTHING.
(10) Connect DRB scan tool to data link connector. The data link connector is located in passenger compartment, below and to left of steering column.
(11) Gain access to SET SYNC screen on DRB.
(12) Follow directions on DRB screen and start engine. Bring to operating temperature (engine must be in “closed loop” mode).
(13) With engine running at idle speed, the words IN RANGE should appear on screen along with 0°. This indicates correct position of oil pump drive.
(14) If a plus (+) or a minus (-) is displayed next to degree number, and/or the degree displayed is not zero, loosen but do not remove hold-down clamp bolt. Rotate oil pump drive until IN RANGE appears on screen. Continue to rotate oil pump drive until
achieving as close to 0° as possible. The degree scale on SET SYNC screen of DRB is
referring to fuel synchronization only. It is not referring to ignition timing. Because of this, donot attempt to adjust ignition timing using thismethod. Rotating oil pump drive will have no effecton ignition timing. All ignition timing values are controlledby powertrain control module (PCM).
(15) Tighten hold-down clamp bolt to 23 N·m (17 ft. lbs.) torque.

Sexton

I appreciate the response ^^

I did have those instructions and used those to reinstall the oil pump drive the second time. However, I did not have the part about rotating the oil pump drive to a certain degree.

I guess the only way to get it dead on would be to have a DRB scanner :-/

Maybe I can keep rotating it until it smooths out? I know that rotating the assembly only modifies the fuel timing rather than the ignition timing. I would imagine that is why Donnie K is saying that the holes dont line up, because after rotating the assembly it would no longer line up.

Sexton

After re-installing the CPS twice, and adjusting it slightly to left and right; I still have this misfire.

I drove the jeep up to the parts store and they ran the codes and it was giving me all kinds of codes about the injector circuits being open. But I think by me pulling the injector plugs (finding which cylinder was misfiring) it caused those codes to pop up.

While I was there, I threw in brand new plugs (they didnt have NGKs or Champions :-/ so I had to put in Autolites) this made no difference. I also talked to the guy and he let me install a brand new coil pack to see if that made any difference. Still nothing, the miss didn't change cylinders and was just as constant as ever.

I pulled the battery, reset the codes and went to drive it around the block to see if I could get new codes to pop up and have them checked again (This time without pulling the injector plugs) and they wouldn't come up and it was late. So I left, and on the 2 mile drive home, the lights came back up. I parked it in the garage, and that is where its been ever since, I'd really like to get the jeep back out on the road, but can't think of anything else that could cause this issue.

My next step would be to replace the fuel rail, I have a spare fuel rail so its not something that is gonna cost me anything, but I figured it would be worth a shot. But why would only the 1 and 6 cylinder misfire, and wouldn't it be a little less consistent if it were a fuel issue?

Also the spark plugs are light brown, as if there is no fuel to these cylinders.

Any more suggestions would help out alot!

JJCIII

I would get a spark tester and check spark. But it sounds like you have an injector issue, you will have to test the power and ground to them.

Radi

Have you tried swapping injectors 1&6 with perhaps 2&5 to see if the problem stays or follows? Not unheard of for wires to break in a harness after jockeying it around to swap engines either.

You should have +12V at one of the pins in the injector connector, the PCM switches the other pin to ground to open the injector. You can check the "ground" pin with a DVM set to DC volts, positive test lead on battery +. Should see no voltage with the key off, and something less than 12V while cranking.

Kalali

The only other clue I can think of is that the three coils in the coil pack fire 1 and 6, 2 and 5, and 3 and 4 plugs at the same time. If your problem is spark delivery as opposed to fuel, that would point to the coil pack or connector wiring.

Sexton

I know its been a while guys, I apologize but other things came up and the jeep has been sitting. I have gone through you guys' recommendations and appreciate all the input everybody has given, hopefully with a little more this jeep can be back on the road soon.

I took your advice and checked the injector plugs, didn't go to injector 6, but I did check injector 1 and two just to see if there was a difference in readings. While cranking, one of the pins had a varying voltage between .07 and .20 volts while the other had a full 12v from the battery. This was compared to cylinder two and it too had the same readings. So I ruled the injector out and figured that the spark plugs being light brown would be a result of the computer possibly turning the cylinders off to prevent flooding as some sort of "limp mode"?

Next, I went to the coil rail. I pulled the rail off the plugs and pulled the fuel pump relay. Had my girlfriend crank the engine while I checked each plug boot for spark, wouldn't you know it cylinder 1 and 6 do not have ANY spark. So I would then assume from these results that the motor is not "Out of Time" but rather that the coil pack is bad, or the coil pack is not receiving a signal to fire. But judging from the fact that the guy at the parts store let me put a brand new coil pack on to test it which yielded the same results of cylinder 1 and 6 misfire, I can assume that the coil pack is not receiving a signal for some reason.

Next question, ( Kalali ) you mentioned that cylinder 1 and 6 are fired off the same coil inside the coil pack. This could probably meant that there is some wire that has been broken inside the harness somewhere. Where did you get the information that cylinder 1 and 6 are fired off the same coil? And could you please tell me which wires control that specific coil inside the coil pack plug? I would like to test the wires going to the coil pack next.

BTW, the only tool for testing voltage that I have is a multi-meter. And pardon my ignorance as to its full potential, my knowledge of its use is minimal, I know how to test for AC and DC voltage but thats about it.

NathanJ

I might have missed this but did you check the plug wires? Are they snapped in all the way? Sorry for being trivial as I am new to this myself.

Sexton

IT RUNS!!! Amazing how two wires can cause soooo much grief.

My problem was that the wires that went into the back of the coil rail were old and the rubber shielding that covers the actual copper wire had broken on several of the wires back there, well two of the wires were touching each other bare copper to copper. I taped all the wires up and covered them again and she runs like a top!

Thanks soooo much for all the help, an extra thanks to Kalali if it weren't for your mention of 1 and 6 running off one coil I probably wouldn't have assumed that it was wiring to the coils.

Now on to smaller stuff that I'll research and look into. Thanks again!

Sexton

And btw Nathan, thanks for the input first off, but just letting you know, the 2000 and 2001 cherokees came with a coil on plug configuration where there are no wires.

Thanks again for the input! Its exciting news to have the jeep alive again after months of downtime.