• Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

2000 Cherokee 4WD 4.0 Backfiring through Intake

Oh man, sorry you wasted money....on the bright side, you will eventually need one.

BTW, my camshaft position sensor and oil pump drive went bad also. In my case what happened was that metal tab on top of the oil pump drive broke off somehow. I just removed sensor and oil pump drive and replaced in the same position. My repair did not involve a scanner. Now I wonder if my timing is off? Mine runs good??

BTW, having another Jeep handy to switch known good sensors before spending money has been invaluable. Do you know anyone else with your model year?
 
boncrshr said:
Oh man, sorry you wasted money....on the bright side, you will eventually need one.

BTW, my camshaft position sensor and oil pump drive went bad also. In my case what happened was that metal tab on top of the oil pump drive broke off somehow. I just removed sensor and oil pump drive and replaced in the same position. My repair did not involve a scanner. Now I wonder if my timing is off? Mine runs good??

BTW, having another Jeep handy to switch known good sensors before spending money has been invaluable. Do you know anyone else with your model year?
Click to expand...


Nope, no one I know has a similar Jeep.

I did get out today and I finally pulled the CMP drive gear and checked the actual gearing and pin for damages. Other than same slight wear everything looked good.

I marked it in numerous places and pinned the top part to be sure it went back exactly how I pulled it.

One question I pose to the forum with everyone so knowledgeable.

Could I retard or advance the timing on this gear by moving it slightly forward or backwards to possible "trick" or actually fix this repair, if in fact it could be off slightly?

Seems unlikely since the gears look pretty good and no teeth are missing that it would have jumped a tooth. But I guess anything is possible.
 
Talyn said:
Why not just find TDC and install it correctly, not as it was?

Did you check the cam gear as well?
Click to expand...

It was installed correctly and was at the right spot. Before I pulled it I marked it and verified the piston was at TDC on the compression stroke and the marks on the crank dampner was at 0*.

So it was in time and correct.

And by cam gear do you mean the timing chain gear? No I have not checked that.
 
When it is installed with motor at TDC does the plug in to the cam sensor point straight back at a 90 degree angle to the motor?
The plug should face to the rear of the motor pointing straight at the bellhousing.
If it doesn't it isn't in properly
 
If the toothpick fits, the Cam sensor and the timing chain are fine and need no scan tool adjustment. Base timing is set by the Cam Sensor and the toothpick. Final timing is comtrolled by the ECU. There are no timing adjustments possible.

Don't get sensor tunnel vision, if you have have a sensor code, either the sensor is faulty or the data is not getting to the ECU. You could have an open circuit, or a short circuit in the wiring. The 5 volt sensors are all on the same circuit. If you have a short somewhere in the system, one or more more sensors may be effected. Care full inspect the sensor sire plugs and sensor wires for corrosion, mis-aligned pins, chafed/melted insulation, faulty wire splices, or damaged wire.
 
Last edited:
Hate to be a downer, but why are you throwing sensors at it? Check your compression, I haven't seen that mentioned yet.
 
doh. Apparently I can't read :dunce:
 
Another easy thing to check for is for a clogged cat. I don't know if there is an easy way to take off the exhuast on that year cherokee.
 
Tim_MN said:
If the toothpick fits, the Cam sensor and the timing chain are fine and need no scan tool adjustment.
Click to expand...

I am glad to hear that, was dreading having to pull the cover and replace timing chain and gears.

I have checked the wiring harness, grounds and connectors.


kastein said:
doh. Apparently I can't read :dunce:
Click to expand...

No worries, I wouldnt mind repeating myself. You guys are just trying to help. Anything at this time is help, even if its a repeat.

sidewaysstarion said:
So do you think you can take some video so we can see and hear what it's doing?
Click to expand...

I can probably do that.

Right now I found someone who has an exact copy of my Jeep (2000, 4.0, 4WD, Automatic) who I am going to pay $20 and a 6 pack to come over Sunday and let me pull their computer and swap out with mine to verify it isnt the PCM.

I dont know him personally, he is a friend of a friend. So both are coming over to split the 6 pack and I will be doing the work.

Again, $20 is worth it to me to rule out or verify something as major as the PCM and end this headache.

IH392 said:
Another easy thing to check for is for a clogged cat. I don't know if there is an easy way to take off the exhuast on that year cherokee.
Click to expand...

Funny you mention that, had a co-worker who has an Explorer started doing similar things and that was his problem. I dont know how hard it is to inspect that, but it gives me something else to go on.
 
stonedv8 said:
.....found someone who has an exact copy of my Jeep ........ let me pull their computer and swap out with mine to verify it isnt the PCM.
Click to expand...

Just make sure neither Cherokee has the Jeep SKIM anti-theft module with gray keys or somebody will be buying a new PCM.

.
standard.jpg
 
Tim_MN said:
Just make sure neither Cherokee has the Jeep SKIM anti-theft module with gray keys or somebody will be buying a new PCM.

.
standard.jpg
Click to expand...

Thanks, I know mine doesnt.

Will call the other guy tomorrow and make sure, dont need him to head over here if his does.

Anyways, I did promise that by swapping the PCM's out and something happens to his, I would replace it. But I dont want to if I dont have too.
 
Well, friend of a friend called me at work today. Seems he had something come up and wouldnt be able to come over Sunday.

Asked him to stop by tonight and I would hurry up and swap it out and see whats up.

He made a quick $20 and I bought him dinner instead of the 6-pack.

Good for him, bad for me.

Still backfiring. Nothing has worked yet, Im at a loss.

Will check into the catalytic converter idea as suggested above.
 
You must log in or register to reply here.

Similar threads

O
2000 XJ Failed Colorado Emissions high CO
2
Replies
27
Views
2K
Ken M
K
L
Realistic MPG 4.0/AW4 33's with 4.56 gears
Replies
12
Views
208
Black_Black
B
I
2000 Cherokee XJ Misfire Mystery
Replies
12
Views
218
Tim_MN
Tim_MN
Cox89XJ
89 Limited 4.0 auto 4wd barely runs
Replies
17
Views
3K
Hypoid
Hypoid
I
High idle, smells like gas, running out of things to replace
Replies
2
Views
2K
Inverhyt
I
Back
Top