Novak Conversions Jeep Wrangler TJ radiator

2000 TJ 2.5 automatic crank but no start

MeIzLinsi

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Jan 6, 2025
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Corpus Christi, TX
Ok, I'm desperate for a definitive diagnosis for my 00 TJ 2.5 AT.
What happened: driving home from work at approx 65 mph, I felt the Jeep stumble a few times like it was missing or something. It recovered for a minute or two then suddenly lost power, sounded like it was backfiring horribly (if I didn't know any better, I'd swear I had flames shooting from my tail pipe based on the sound alone). I pulled over and it was running but barely, I touched the gas pedal and more popping/backfiring, so I shut it off. It has been known to fail to start OR start and run like dog shit after driving a while and shutting it down then restarting within 10 minutes or so. I let it sit for an hour before I ever tried to restart it and only after raising the hood to check for obvious issues. It did not restart and hasn't since.

What I've done so far: checked fluids, fuses, relays, and codes. I had previously been throwing O2 sensor codes and am in the process of replacing them. After I got it home, I had a P0340 and a P0351. The ignition coil went bad last year and was replaced, but I replaced it again along with the camshaft position sensor/pick up coil) and the crankshaft position sensor. I have NO spark whatsoever. Cap and rotor are fairly new as is distributor, and upon inspection, I see no reason to believe that's my issue. Fuses and relays are all good, I'm getting my 5v reference and 5v signal back to the PCM from CKP, I have 45psi at the fuel rail, ASD relay circuit seems fine, checked grounds, wiring harness behind block where I've read it's been known to get damaged, and repaired my CKP connector as one wire was questionable so I figured why not. I've checked and I have voltage at my ignition coil both with key on for a few seconds and then again while cranking the 12v returns and remains while being cranked. My plug wires are within specs when testing resistance, and I feel like I'm chasing my tale. I replaced my time chain last year, and I don't hear it slapping around in there so I don't think that's my issue. I have occassional sticky ignition syndrome where if I don't wiggle the key just right before starting, it will start but I have no accessories like radio or AC and the airbag light stays on, it's fixed by shutting it off, jiggling the key and restarting. This happened a handful of times in the past year and has never been the cause of a no start condition. I have considering replacing the ignition in its entirety and then the distributor itself but I can't keep throwing parts at it. I've put well over $1000 in it in the last 2 months. Several people have said my PCM is bad.

Work that has been done recently that I feel is unrelated but worth mentioning: 4 days before this happened, I pulled it out of my garage after rebuilding my rear differential (super proud of that success, btw, as everyone said I couldn't because I'm a girl), a month before that I replaced the exhaust manifold for the second time in 4 months as it backfires due to some kind of vapor lock and cracked the new one, also I've recently put in a sound system, replaced AC control module, blower motor and resistor, radiator, idler pulley, alternator, battery, motor and transmission mounts, and I think thats it but I might be forgetting something. Again, I don't feel any of that is pertinent but I figured I'd mention just in case.

Sorry for the novel, but I don't want to waste anyone's time by not explaining everything.

Thanks in advance for your time.
 
The fact that you have no spark is a significant clue. Since you've already replaced the ignition coil, camshaft position sensor, and crankshaft position sensor, I’d suggest checking the following:

**Check the PCM Connections**: Ensure that the connections to the PCM are secure and free of corrosion. Sometimes, poor connections can lead to intermittent issues that are hard to pinpoint.

**Ignition Switch**: Given the sticky ignition syndrome you mentioned, it might be worth focusing on the ignition switch. A faulty ignition switch could cause intermittent power loss to the ignition system, leading to no spark.

**Wiring Issues**: You mentioned checking the wiring harness behind the block, which can often be a trouble spot. It’s worth doing a thorough visual inspection of the entire wiring harness for any signs of wear, chafing, or corrosion, especially in tight spaces where wires can rub against the body.

**Crankshaft Position Sensor Signal**: Since you’re seeing the correct voltage at the ignition coil, it’s important to confirm that you have the proper signal coming from the CKP sensor when cranking. If you have access to an oscilloscope or a good multimeter, checking for a clean signal could help confirm it’s functioning properly.

**Look for Codes**: If you have a good scanner, check for any hidden or pending codes that could provide additional clues. Sometimes, a faulty component can throw codes that might not seem directly related.

**Vacuum Leaks**: Though it's more of a running issue, check for any vacuum leaks that could be causing backfiring or stalling under load.

**Fuel System**: While you have pressure at the rail, it might be worth confirming that your fuel injectors are firing. You can do this with a noid light or by a simple check if you have tools available.

If all else fails, considering that you've done so much already, a professional diagnostic might be a good way to go. Good mechanics have access to specialized tools and experience that can be worth paying for.
 
Thank you for that informative reply. I appreciate you taking the time to do so. So I have checked the PCM connectors as well as pulled the fuse box up out of the plastic it sits in and check the underside for corrosion as I've had a vehicle in the past that had that had this issue and it turned out to be a corroded wire under the fuse box and they charged me $700 to solder one wire and that's why I'm so reluctant to take it anywhere. Without a 3rd leg, females are an easy target and they do dumb things like try to sell us blinker fluid. Haha just kidding but seriously I'm trying to avoid the shop but you may very well be right. I'm starting to agree that it may just be something above my level of experience.

The ignition switch is something that keeps Weighing on my mind and I really think that you might be on to something there. I was under the impression that the ignition actuator could be at fault as well and I believe I even heard that it was more likely that it would be the actuator than the switch. Is there a way to test the ignition switch? If possible, could you lay out the steps for me to do that and I will do that today? If not, would you recommend changing just the ignition switch or the ignition switch, actuator and lock cylinder as well? My key does have a chip so I would have to have it programmed and with it being stuck in my driveway that might be kind of taxing.

If it's not too much trouble, could you lay out the steps for checking the signal from the ckp while cranking just to make sure that I've done this right. It's my understanding that while a partner is cranking to obviously back probe the crankshaft position sensor connector signal wire and I should see a fluctuation from 0 volts to 5 volts. I did try this and with a multimeter it was hard to tell if it was fluctuation like it should be or not. In turning the motor over by hand however, there was fluctuation, though I can't tell you for sure if it was the nice pretty square waves that you would see on a screen if you had the right tool to check it.

As for codes, I had to remove my battery the other day to have it charged because in all the testing it was drained and I know that I couldn't get accurate results with a less than full battery. There were no codes when I disconnected the battery as the ignition coil code and the camshaft position sensor code had already gone away on their own. Maybe this is worth mentioning, I have seen two codes for an IAC issue. I believe one was P0505 and I'm not 100% sure what the other one was. I believe it was different but I can't say for sure and I am fairly certain it was due to disconnecting the PCM connector when testing for my voltages or continuity, or the fact that I have my air box off. These codes were not present when the issue initially arose so I figured that was just caused by me while testing.

I do not have the thing mentioned to check to see if injectors are firing, but I do smell fuel when cranking so I assume that they're working correctly but I do know what assumptions get you. I will look into that.

Is there a procedure or certain things that I can get my multimeter out and check to test my pcm? I know it's putting out a ground to the ASD relay or I would lose my voltage at my ignition coil and injectors when cranking. I also have a 5 volt reference from the PCM. But I don't know that it's doing everything else it's supposed to do. I really don't want to drop $400 on a PCM unless I know for sure.

Thank you again for your time. I super appreciate all the help and advice.
 
@TJason05

So, I replaced my ignition switch and attempted the actuator, as well. Several times I tried to get it to function and finally it went back together but the key was near impossible to turn and still no start. I wasn't convinced so I put my old actuator in with the new switch and the key is worse than it was, but not as bad as it was with that new actuator. Still no start. My lock cyclinder I believe is toast. The key comes out with it in the run position I found out in this whole ordeal. I don't believe that would be the cause of no spark, though, as it still turns the engine over.

The only thing left beside the PCM is the distributor itself, and given the backfiring it did, it makes since. There goes throwing more parts at it without a definitive diagnosis. I'm devastated and so incredibly frustrated. :(
 
I would consider a mass air flow (MAP) sensor failure as a possible cause of your backfiring issues. For the no spark problem it seems the distributor is all that you haven't replaced. I would buy a new cap and rotor first and try that. If that's not it, well, you have a new cap and rotor for the new distributor you are about to buy. For possible PCM issues Wranglerfix will test yours for you, give them a call.
 
The cap and rotor are new and visually, I see no reason they need to be replaced. I'm getting power to my coil while cranking, just no spark.

I actually just got off the phone with Mark. Extremely nice guy and very helpful. I'm going to send my pcm to him with the hope that it can be repaired.

As for the MAP sensor, definitely worth looking at since the backfiring has been an issue for some time and long before this happened. Is there a way to test the sensor or do I just have to replace it?

Thanks.
 
@Wranglerfix

So, I put my PCM in another TJ and it fired right up. I was thinking distributor but I realized that a bad distributor wouldn't cause no spark from the coil, especially since I have voltage there when cranking, it would just not distribute spark to the plugs. Now what? I'm pretty much back at square one.
 
If I understand this correctly, no. The coil has battery voltage while cranking, which means it should then send higher voltage to the distributor (spark) which then distributes to the plugs. I have no spark so I must not have power going to the distributor. I have the 5v reference at the camshaft sensor inside the distributor. Am I missing something?
 
Might want to ohm and continuity check all your wires from the distributor back to the PCM...or de loom the wiring harness and visually inspect everything including your grounds.

Me personally I might consider throwing a distributor at it...or at least making sure it's lined up with the right pin hole...my understanding is there's one for the 4 and one for the 6.

-Mac
 
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If I understand this correctly, no. The coil has battery voltage while cranking, which means it should then send higher voltage to the distributor (spark) which then distributes to the plugs. I have no spark so I must not have power going to the distributor. I have the 5v reference at the camshaft sensor inside the distributor. Am I missing something?

No spark at the plugs doesn't necessarily mean there is no power going from the coil to the distributor. Power could be going to the distributor but not making it beyond there.

Test the coils output. I know you replaced it but bad parts are out there. If good then look at the connection to the distributor. Next check the distributor. With the cap off is the shaft spinning and the rotor rotating? You have the rotor lined up properly? Cap properly positioned? Was it reassembled correctly after you swapped the camshaft sensor? Also, look again at the ASD relay. Did you try swapping the existing relay with another?
 
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Ok, I'm desperate for a definitive diagnosis for my 00 TJ 2.5 AT.
What happened: driving home from work at approx 65 mph, I felt the Jeep stumble a few times like it was missing or something. It recovered for a minute or two then suddenly lost power, sounded like it was backfiring horribly (if I didn't know any better, I'd swear I had flames shooting from my tail pipe based on the sound alone). I pulled over and it was running but barely, I touched the gas pedal and more popping/backfiring, so I shut it off. It has been known to fail to start OR start and run like dog shit after driving a while and shutting it down then restarting within 10 minutes or so. I let it sit for an hour before I ever tried to restart it and only after raising the hood to check for obvious issues. It did not restart and hasn't since.

What I've done so far: checked fluids, fuses, relays, and codes. I had previously been throwing O2 sensor codes and am in the process of replacing them. After I got it home, I had a P0340 and a P0351. The ignition coil went bad last year and was replaced, but I replaced it again along with the camshaft position sensor/pick up coil) and the crankshaft position sensor. I have NO spark whatsoever. Cap and rotor are fairly new as is distributor, and upon inspection, I see no reason to believe that's my issue. Fuses and relays are all good, I'm getting my 5v reference and 5v signal back to the PCM from CKP, I have 45psi at the fuel rail, ASD relay circuit seems fine, checked grounds, wiring harness behind block where I've read it's been known to get damaged, and repaired my CKP connector as one wire was questionable so I figured why not. I've checked and I have voltage at my ignition coil both with key on for a few seconds and then again while cranking the 12v returns and remains while being cranked. My plug wires are within specs when testing resistance, and I feel like I'm chasing my tale. I replaced my time chain last year, and I don't hear it slapping around in there so I don't think that's my issue. I have occassional sticky ignition syndrome where if I don't wiggle the key just right before starting, it will start but I have no accessories like radio or AC and the airbag light stays on, it's fixed by shutting it off, jiggling the key and restarting. This happened a handful of times in the past year and has never been the cause of a no start condition. I have considering replacing the ignition in its entirety and then the distributor itself but I can't keep throwing parts at it. I've put well over $1000 in it in the last 2 months. Several people have said my PCM is bad.

Work that has been done recently that I feel is unrelated but worth mentioning: 4 days before this happened, I pulled it out of my garage after rebuilding my rear differential (super proud of that success, btw, as everyone said I couldn't because I'm a girl), a month before that I replaced the exhaust manifold for the second time in 4 months as it backfires due to some kind of vapor lock and cracked the new one, also I've recently put in a sound system, replaced AC control module, blower motor and resistor, radiator, idler pulley, alternator, battery, motor and transmission mounts, and I think thats it but I might be forgetting something. Again, I don't feel any of that is pertinent but I figured I'd mention just in case.

Sorry for the novel, but I don't want to waste anyone's time by not explaining everything.

Thanks in advance for your time.
Had a very similar issue you’ve described in my 97 4.0 5spd with the same codes (and I think a P0158/P0159) after fixing a crank no start issue caused by faulty wiring to the cam position sensor that cut spark (found frayed wires under plastic wire coverings). When driving, especially going over rough roads, bumps or turns at higher speeds, the rig would go limp then proceed to backfire a few times before going back to normal for a bit and would repeat until pristine road conditions… it is worth noting that I went with a NAPA replacement or Standard Motor cam sensor but the electrical fitting to the pickup was looser than it’s OEM counter part and my problem was fixed as soon as I zip tied the connection to have no play.

Since you mention replacing a lot of your ignition components would you happen to know what brand was used, especially for your cam position sensor? I’ve heard a lot of stories and have personally encountered (when chasing crank no start issue) that sensors from Amazon or big name parts stores go bad out of the box or fairly quickly and only brands such as NTK or Standard Motor/Napa Echlin yield good results.

Thinking your cam position sensor was on its way out and causing similar backfiring issues to my previous problem and perhaps has fully died causing crank no start?
 
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I use NTK/NGK when I can, though I dont recall which brand of sensor I used for the camshaft, I believe it came from Napa or Advance. After owning a Jeep, I have learned to shy away from oreillys and autozone parts.

I'm a little confused on the coil, I think. I hooked up a spark tester on the wire that goes from coil to distributor, it has no spark. So, I know I won't see spark from my distributor to my plugs, but I checked anyway just to confirm. I was correct. The only wires from the distributor are those for the camshaft position sensor, and I have verified that signal from both crank and cam sensors is reaching the PCM. With that, obviously, they are getting the 5v reference signal as well.

Ah, the distributor. My gut has been screaming at me that the problem lies here. I keep telling myself that it can't be because my coil would still fire TO the distributor, though. I will likely just go ahead and throw a new one in anyway. (Matter of fact, I will go and get one now and let yall know)
 
The Jeep is running once again!! The lesson learned here is to always go with your gut. After planning to buy a distributor and report back, I once again talked myself out of that being the issue. I rechecked timing, went through the wire harness in its entirety (again), then checked, rechecked, played with ignition components some more, and finally pulled the distributor cap to recheck rotor and pick up coil. When removing the pick up coil, with it came the pulse ring. Bingo. There's been my issue the while time. I have a distributor ordered but I was too excited to wait. I super glued the pulse ring back to the distributor and put it back together. She fired up immediately and after coughing out the cobwebs, runs great.
 
I was in a hurry to post the good news earlier but now that I have a second, I wanted to thank those that took the time to reply with advice and guidance when I was beyond frustrated and beginning to feel hopeless. I very much appreciate yalls time and words of wisdom. :)
 
I was in a hurry to post the good news earlier but now that I have a second, I wanted to thank those that took the time to reply with advice and guidance when I was beyond frustrated and beginning to feel hopeless. I very much appreciate yalls time and words of wisdom. :)

Glad you were able to fix it, hopefully she runs for plenty longer!
 
Novak Conversions Jeep Wrangler TJ radiator