2000 4.0L Auto stalls occasionally while driving

[Jaxon B.]

Not my TJ, but my brother's. He has a 2000 4.0L Automatic Sahara Package (though I don't think Sahara makes much a difference in diagnosing this lol).

He calls me and tells me that he was going down the highway when all of the sudden his tach drops to 0 and he starts losing speed similar to if you were to just push the clutch in and glide. He pulls off to the breakdown lane and restarts the Jeep and it goes up and drives just fine. This wasn't a one-off thing though, he told us that it happened 4 times today.

If it helps he just got his battery replaced yesterday, the old one was 3 years old and leaking. He also said that all of the accessories were still on after the engine died, like the radio and blower motor etc.

I'll see if I can post pictures and check fluids, gonna have it at my house later today to bring it to a mechanic friend. Tell me what could be wrong just to bring it up as suggestions to him!

 

[harbiison]

Not my TJ, but my brother's. He has a 2000 4.0L Automatic Sahara Package (though I don't think Sahara makes much a difference in diagnosing this lol).

He calls me and tells me that he was going down the highway when all of the sudden his tach drops to 0 and he starts losing speed similar to if you were to just push the clutch in and glide. He pulls off to the breakdown lane and restarts the Jeep and it goes up and drives just fine. This wasn't a one-off thing though, he told us that it happened 4 times today.

If it helps he just got his battery replaced yesterday, the old one was 3 years old and leaking. He also said that all of the accessories were still on after the engine died, like the radio and blower motor etc.

I'll see if I can post pictures and check fluids, gonna have it at my house later today to bring it to a mechanic friend. Tell me what could be wrong just to bring it up as suggestions to him!

I’ve actually struggled with this before. I had stopped at a stop light in drive and my whole engine shut down i threw it in park then turned it over again and it went hasn’t done it since.

 

[Jaxon B.]

I’ve actually struggled with this before. I had stopped at a stop light in drive and my whole engine shut down i threw it in park then turned it over again and it went hasn’t done it since.

Sounds similar, but my brother was in drive going down the highway, probably going 75-80 knowing him.

But you are right, shutting the engine and turning it over works just fine and is a temporary solution, but something has to be going wrong in the engine. I looked through your build thread, and saw you pulled your engine, was there anything outstanding in there relating to that?

I just have a gut feeling the issue with my brother lies in the trans.

 

[Jaxon B.]

Just checked the 2000 FSM

Guess i'll check these...

 

[Jaxon B.]

So update, we brought a mechanic friend over and nothing seemed to be wrong inside the engine. Him and my dad drove around the neighborhood for about 15 minutes to try and recreate the issue with a fuel pressure meter attached but couldn't get it to stall. Since then, it hasn't happened even once until today, where it happened again.

This time my brother added that it only would happen on right turns, and my dad thought maybe a rollover sensor may be going off under the battery, but the only sensor I know of under there is that temperature sensor.

 

[nbarb]

Check if the battery is secured
all the way. It could be bumping up against the fender and shorting causing the engine to shut off

 

[nbarb]

edit; that posted twice. oops

 

[Jaxon B.]

Check if the battery is secured
all the way. It could be bumping up against the fender and shorting causing the engine to shut off

My dad just got back with my brother's car, he said he found a wire that is connected to the PDC and was caught under the battery. It was stripped bare and might be shorting to the battery plate. I think that might cause the issue, what do you think?

 

[nbarb]

My dad just got back with my brother's car, he said he found a wire that is connected to the PDC and was caught under the battery. It was stripped bare and might be shorting to the battery plate. I think that might cause the issue, what do you think?

That sounds exactly like something that could cause the issue you described

 

[Jerry Bransford]

My dad just got back with my brother's car, he said he found a wire that is connected to the PDC and was caught under the battery. It was stripped bare and might be shorting to the battery plate. I think that might cause the issue, what do you think?

The only wire that goes under the battery plate is for the battery temperature sensor. It's unlikely to be able to cause the engine to die but I'd look to see if the sensor is still there, it's a small round disk that senses the battery temperature and it serves an important task. Its job is to insure the battery isn't getting too hot while being charged and if it does get too hot, the PCM turns the alternator's charge rate down. It does need to be there so if the sensor has been torn away I'd replace it.

But onto the engine stalling, it could be something like the crankshaft position sensor which is mounted on the transmission bell housing where it bolts to the engine. The CPS picks up pulses from the flywheel and generates the engine's master timing signal. If the CPS goes bad the engine will die suddenly. No guarantee the CPS is the cause of the problem but it'd be in the top 2 or 3 most likely.

No check engine light after it dies or stored diagnostic codes? See if there are any by having him quickly turn the ignition switch on-off-on three times within five seconds and then leave it in the on position. That will start the built-in diagnostics and if it finds any error codes they'll start displaying in the odometer. If that procedure was done correctly it will always display a '55' code which only says the diagnostic routine is complete and no more codes follow.

 

[Jaxon B.]

So we tested the cable and it would short but not stall the engine; we fixed it anyways, but it was not the issue. While looking at the other things we noticed that the automatic shutdown relay looked a little... off. We pulled it while it was running and it stalled in the same way that my brother described. Ended up swapping it for the hopefully-good horn relay and drove just fine after that.

I hope that is the end of the problem! lol

 

[Jaxon B.]

The only wire that goes under the battery plate is for the battery temperature sensor. It's unlikely to be able to cause the engine to die but I'd look to see if the sensor is still there, it's a small round disk that senses the battery temperature and it serves an important task. Its job is to insure the battery isn't getting too hot while being charged and if it does get too hot, the PCM turns the alternator's charge rate down. It does need to be there so if the sensor has been torn away I'd replace it.

But onto the engine stalling, it could be something like the crankshaft position sensor which is mounted on the transmission bell housing where it bolts to the engine. The CPS picks up pulses from the flywheel and generates the engine's master timing signal. If the CPS goes bad the engine will die suddenly. No guarantee the CPS is the cause of the problem but it'd be in the top 2 or 3 most likely.

No check engine light after it dies or stored diagnostic codes? See if there are any by having him quickly turn the ignition switch on-off-on three times within five seconds and then leave it in the on position. That will start the built-in diagnostics and if it finds any error codes they'll start displaying in the odometer. If that procedure was done correctly it will always display a '55' code which only says the diagnostic routine is complete and no more codes follow.

Tried to get it to do a code but the odometer wouldn't read anything other than the mileage. Apparently after I looked it up it only works on some 2000 models? I don't know how true that is but we hooked up an OBDII scanner and saw nothing. CPS didn't throw anything and there was no check engine light which I think a bad CPS would do.

 

[Jerry Bransford]

Tried to get it to do a code but the odometer wouldn't read anything other than the mileage. Apparently after I looked it up it only works on some 2000 models? I don't know how true that is but we hooked up an OBDII scanner and saw nothing. CPS didn't throw anything and there was no check engine light which I think a bad CPS would do.

'98 to early 2000 models cannot generate their own diagnostic trouble codes. Did the external code reader you plugged in indicate anything at all to confirm it's at least talking to the engine computer?

 

[Jaxon B.]

'98 to early 2000 models cannot generate their own diagnostic trouble codes. Did the external code reader you plugged in indicate anything at all to confirm it's at least talking to the engine computer?

Yep, we were able to read all engine vitals and it was up to date with the things like tachometer etc. His 2000 was an earlier one as well, I think in November of '99 it was produced.

 

[harbiison]

My Jeep ran into this issue again this morning along with seems to be a slip in the trans? I had read it could possibly either be the PCV or even how the timing was adjusted. I only think I might need a trans rebuild.

 

[Jerry Bransford]

My Jeep ran into this issue again this morning along with seems to be a slip in the trans? I had read it could possibly either be the PCV or even how the timing was adjusted. I only think I might need a trans rebuild.

If your engine is stalling that's no sign that your transmission needs to be rebuilt. You have the 32RH automatic transmission and it wouldn't cause the engine to just stop running without any drama. The PCV won't cause that and the engine timing is not user adjustable like things used to be your engine is set by the engine computer. Possible causes include a bad crankshaft position sensor, camshaft position sensor, fuel pump, etc.

On your transmission slipping, that might have an easy fix. Check its ATF level, it's common for it to get low on ATF and that will definitely cause slipping. Here's how to check the ATF level... start the engine and keep it running. Set your parking brake then shift to Neutral. The engine MUST be running and the transmission MUST be in Neutral NOT Park while checking its ATF level. Then check its level with the transmission dipstick that comes out from under the passenger side of the firewall. The level must be all the way up to the top full mark. If it's low, insert a small funnel into the dipstick tube and add enough ATF+4 to get it full. It's also better to be slightly overfilled than underfilled. And if the ATF bottle doesn't say "ATF+4" in big letters on the front of the bottle it's the wrong type of ATF. No, not even Mobil-1 ATF is the right stuff, it has to be ATF+4 in a Wrangler automatic transmission.

 

[Jaxon B.]

Was inactive for a bit due to exam season, but now I'm back! With more problems!

Brother came by again saying it stalled twice while driving, gonna replace the CPS and see how that goes.

He has a transmission leak elsewhere that has gotten pretty bad, so we are going to bring it to a mechanic to get that fixed up. Hopefully just a 5 dollar seal.