No bus and randomly stalling

[thisismyusername]

I'm having an issue about which I've read some other threads but I wanted to describe my symptoms and get someone's opinion. For reference, this is a 1999 Jeep Wrangler L6/4.0L.

My jeep has been sitting for a few months in various states of disrepair while I did work on the front end. I took it for a test drive last week, drove for maybe 30 minutes, took in on the interstate, and everything seemed perfect. I was letting it idle in the driveway to burn off some of the old gas before I filled it back up when it suddenly stalled. I tried to start it, and I could hear it crank, but it just wouldn't start. Additionally, with my key in the ignition, none of my gauges would move but my check engine light did come on. All my lights and stereo would come on and I'm certain my battery is good. I let it sit for maybe 20 minutes and tried again and it started right up.

I suspected a bad chassis ground somewhere but I measured the negative battery terminal to every chassis ground I could find and they all seemed fine. I installed a kill switch inline with the fuel pump relay maybe a year ago and cleaned up a lot of the wiring in that process, so I suspect it could also be a harnessing problem.

Today I got another chance to take it on a drive after not having driven it for a week, and it ran fine for maybe 30 minutes. I went and got gas and started it back up again. I drove maybe 20 feet and it suddenly stalled again while I was driving. Same issue as before, none of my gauges would read anything and my check engine light was on. I left the key in for another minute or so and it flashed a no bus error (see the attached picture). I called a tow truck to get me back home, and when it arrived maybe 30 minutes later I checked my gauges again and everything seemed fine; it cranked right back up. The temperature, oil pressure, battery voltage, etc... all seemed to read fine.

Based on the this post and this post I'm thinking it's the crankshaft position sensor but wanted another opinion. If it is the crankshaft position sensor, can someone explain to me:

1.) Why is it temperature dependent (i.e. it only seems to be an issue after it's been running for a while)?
2.) Why does it lead to a no bus error?

Thanks!

 

[Vidar]

Did you take your distributor out at any point during your repairs?

 

[thisismyusername]

Did you take your distributor out at any point during your repairs?

Nope. I did not.

 

[Vidar]

Mine was distributor timing related, but that was after a complete engine rebuild. I would pull the crankshaft position sensor, as well as the idle air controller, and clean them up really good.

 

[thisismyusername]

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Mine was distributor timing related, but that was after a complete engine rebuild. I would pull the crankshaft position sensor, as well as the idle air controller, and clean them up really good.

Did you have the same symptoms as me? Stalling after running from a while, followed by a no bus signal, and then after waiting a while, starting back up?

 

[Vidar]

I had random stalling, but it was accompanied by a really rough idle and very hard starts. My issue was that the the timing on the distributor was retarded one tooth, which allowed it to start, but it would miss terribly. Since you mentioned you had been working on it, I figured I’d ask about the distributor.

 

[Halligan693]

Was there ever a solution found? I am having the exact some issue on my 00 TJ 2.5L. Runs good for 30 min then starts to stall out with “no bus” on the dash. Then I let it sit for 5 min on the side of the road and it starts up and goes for about 10 min then it repeats.

 

[Blondie70]

I had the No Bus on mine. I replaced the ignition switch and have never seen it again. Good Luck.

 

[Halligan693]

I had the No Bus on mine. I replaced the ignition switch and have never seen it again. Good Luck.

It's not only the "no bus" issue. It's the exact issue reported in the original post.

Just a quick summary of my symptoms on my 2000 TJ 2.5L with 5 Speed:

1) Starts up and Runs great for about 20 - 30 minutes.
2) Engine bucks once or twice
3) Engine dies a few moments later
4) Tach and Speedo drop to zero
5) Check engine light comes on
6) Odo display says "no bus"
7) Let the truck sit for 5 minutes or so with the ignition off
8) Engine starts back up and runs fine for about 5 to 10 minutes
9) Rinse, Repeat...

Sometimes it runs a little rough once it starts back up after the first cycle. Almost like it's flooded, but it clears out after about 10 seconds and runs and idles fine.

I spoke to my mechanic yesterday and explained the symptoms, and he said that I should start with a Crank Position Sensor. If that doesn't work, it's most likely the PCM. He said either way it's not really a big deal and he's seen this multiple times with these trucks.

There are no codes stored in the PCM either. Outside of this issue, it runs and drives perfectly.

Curious if anyone other than the original poster here has had this issue and what the resolution was.

My son and I purchased this truck two days ago, and the above issue happened on the trip home with it. It wasn't my happiest moment. But it only has 74K miles on it and not a spot of rust anywhere we can see. The frame was also replaced at some point by a previous owner. It has a textured black powder coat on the entire frame. Carfax shows it was in a Moderate/Severe collision to the front left corner about ten years ago. But the frame seems too new for it to be from that. No other sign of residual issue from that hit that I can see. Tracks straight.

 

[Halligan693]

Resolution: After talking to a mechanic, he mentioned that this issue is common and, in most cases, is caused by a malfunctioning Crank Position Sensor. I took his advice and changed the sensor. The issue has not returned. Actually, the engine is running even better than before.