2000 Cherokee 4WD 4.0 Backfiring through Intake

[stonedv8]

Nope. I gave up. Everything I have done I got frustrated and pissed off and I hated coming home seeing it sitting in the carport.

Called a shop and they have it now.

Whatever they find I will let you guys know.

Maybe whatever it is can help someone else in their diagnosis.

 

[behemoth]

Hey, I just read your whole thread and feel your pain!

I'm in the same boat with my 99 XJ not backfiring but misfiring heaps on startup, settles down to a steady misfire when warmed up to temp (not closed loop but proper operating temp). Been doing various sensors and cleaning earths, changed plugs, O2 sensors... looking at dissy next as it's pretty loose on the shaft. Sensors all seem to be operating from what I can tell on the meter.
Fuel pressure check for me next then maybe some seafoam type stuff to clean it out. Gonna pull TB and clean that as well as MAP on the weekend too.

Any updates from the shop? I'd really like to diagnose mine before having to hand it to some shop who are just gonna do all the same crap I've done but charge me heaps for it.... Hope ur getting some progress.

 

[kastein]

That really sucks.

The P1391 has me thinking it may be a wiring harness or ECU issue - those sensors are powered via a regulator in the ECU. If it's the same setup as a 98, you should check pin A17 in ECU connector C1 (an orange wire) and make sure it has 5V at it. If it doesn't, there's your issue. If it does, check at the sensors themselves.

I checked my 01 Dodge Ram Van/Wagon FSM as well, and the connector pinning and wire color for that signal is exactly the same, so I'd be shocked if your XJ doesn't follow this setup too.

I didn't re-read the whole thread 100% carefully, so hopefully this isn't another repeat from me.

The problem is, it may be an intermittent or noisy signal which would only show up on an oscilloscope.

 

[gradon]

Did you make sure the 0* was at the end of the compression stroke(air was blowing out of cylinder 1 sparkplug hole)? If not, you need to spin the crank another 360* to get to that point. If that's the case, the cam sensor is 180* off and there will be backfires and the 1391.

 

[Wlahey]

I have this same problem and I am almost to where you left off...waiting for O2 sensors...any luck? Reading your thread pretty much sums up what i've been going through. I also have the 2000 4.0 Sport with auto, CA emissions (3 cats and 4 O2 sensors). If you've gotten anywhere. HELP ME. ha.

 

[5108696]

I have this same problem and I am almost to where you left off...waiting for O2 sensors...any luck? Reading your thread pretty much sums up what i've been going through. I also have the 2000 4.0 Sport with auto, CA emissions (3 cats and 4 O2 sensors). If you've gotten anywhere. HELP ME. ha.

ANOTHER VICTIM HERE!!

Sorry for yelling, but wanted to get the attention of all of the amazing experts who have been helping stonedV8 with his problem.

I am about to post my entire chronological malfunction history (2000 Sport 4x4) but need some guidance on how / where to do it properly - within forum rules.

Thank you in advance!

Rick

 

[The Badness]

You know, literally every time I've seen a thread on this issue, it goes unresolved ending with a 20 page thread and a pissed xj owner. My 99 has had this problem since I got it at 120k, she has 272k on her and this damned problem still exists. I've replaced every part imaginable, every sensor, timing, I even had the motor rebuilt....still does it. I believe in that movie "iRobot" they explained it as "ghost in the machine"

 

[The Badness]

You know, literally every time I've seen a thread on this issue, it goes unresolved ending with a 20 page thread and a pissed xj owner. My 99 has had this problem since I got it at 120k, she has 272k on her and this damned problem still exists. I've replaced every part imaginable, every sensor, timing, I even had the motor rebuilt....still does it. I believe in that movie "iRobot" they explained it as "ghost in the machine"

 

[kelso1]

As usual no results from new users when they get their issue resolved. I had the exact symptoms on a customers vehicle. It turned out to be poor quality fuel. The sample smelled good. It was a little yellow, but not excessive. We had it weighed. Way to heavy. We shut off the fuel pump and ran a fuel rail flushing tool filled with new gasoline. The vehicle ran perfect. Drained and replaced the fuel in the tank. Fixed.

 

[kelso1]

Sorry, I shouldn't be harsh. We are all here to help each other.