Hello again

In the last couple of days my jeep has just started to do a strange misfire/cutout. You drive along fine and the exhaust pops and then you're straight back to normal power. If you look at the dash, the CEL flashes on too fast to read (I had to stop and check which light it was with the engine off and key in position 2).
Sometimes the loss of power can last about a second and the dash seems to lose power as well with the rev counter/speedo falling towards 0 (CEL goes out again) until power comes back again.
Once, I lost power long enough to worry about steering/brakes so I braked to a halt and as soon as I put the gear lever back into P it started first hit and off I went.

This hasn't caused a major problem so far, but I doubt it will just go away. Does anyone have any ideas as to where I should start with fixing this?
thanks everyone
Morat

 

Given the symptoms, this is going to be a somewhat difficult issue to isolate. That been said, you'll need to fix it before you get into some serious trouble. I'd start by a thorough visual inspection of all the wiring under the hood. Technically you need to first determine if this is a fuel delivery or spark delivery issue and then go deeper. Spark delivery and/or electrical issues typically cause the engine to cut out instantaneously whereas fuel starvation/delivery problems tend to cause a slight stumbling before the engine completely cuts out. Good luck and keep us posted.

 

Thanks for the reply - and yes I think you're right that this will a tricky one to trace. Intermittent faults are the worst
If this was a BMW E30 I'd say it was the DME relay (relay for the engine electronics) but this is a Jeep so I'm just guessing.

Time to have a good poke around the loom then!

 

What year and engine? Since you say the cel does come on, have you pulled the codes?

 

97 4.0
I'll get onto pulling the codes, I've got Torque - but that's it atm.
Morat

 

Yup, retrieving codes is job #1. OBD isn't perfect, but it is awfully darn good at pointing you towards the root cause circuit.

Post the "exact" codes here for comment (not just a description) as with OBD, the devil is in the details.

 

OK, the codes are:
P0700 - Powertrain. Transmission Control System (MIL Request)
P1694 - Powertrain. Multiple Descriptions

For Chrysler/Dodge/Jeep it is: Tachometer Circuit High Voltage.
For Seat/Audi/Volkswagen it is: Malfunction Indication Light Open/Short to Ground.

These are codes from the Torque App, so the descriptions may not marry up with the actual meaning according to Chrysler.

To recap, the Jeep is running just fine 99.99% of the time. Just occasionally (seems to be normally when driving hard) it will cut momentarily and flash the CEL for a split second. The rest of the time it drives as normal, all lights correct. Once so far it has cut out long enough for me to coast to a halt and it restarted just fine.
Last night, it cut as my wife pulled out of a junction and took 3 attempts to restart - that was quite scary.

erm.. help?

 

After a bit of googling I'm starting to suspect the computer for the transmission - but has anyone heard of a fault there that would cut the engine?

 

I'm having the same kind of issue with my 1998 Cherokee. I recently had a hole in the lower radiator hose which sprayed coolant mostly toward the electric fan area. I quickly got some tape around it an got it home. Next couple of days later I got the hose and a new thermostat in. All was well, until I got torque and the OBDLink MX attached and started trying to follow my coolant temp while driving. The '98 has limited info available, compared to newer cars, but still useful when you don't have gauges. One question I would have is: you mentioned Torque, but I would be interested to know if you have had the Bluetooth dongle attached to the car when these things happen. You are supposed to be able to keep it on there even with the car off without any problems, and certainly should be able to use it when running even if you are not actually paired/connected. I'm just wondering if the XJ computer is fast enough to handle continuous reading of info while also handling it's normal operation.

While i did have some probable overheating with the hose issue, I added fluid and it never got very low. I of course don't want to find a cracked head or gasket leak, and since the problem is quite intermittent I am looking at TPS, CPS, possibly O2 sensors or it may need a good throttle body cleaning even though I've looked and could find no noticable fouling from the leaking fluid - nothing in the air cleaner compartment. I have P0700 and P1694 and Alldata does not show a listing for P1694. I did find a general description on this site, for powertrain. I've noticed that my missing and later complete stall with no start would happen down the road when hit a bump or going up or downhill on my steep driveway. I'm aware of grounds, I think I fixed all of them in the past. I will be testing TPS and the CPS but if anyone has ideas about a problem like this that seems to be vibration and/or position sensitive, I am open to suggestions. I will also repost if I find the actual problem.

 

Although it was not a Jeep I had a similar problem with a car so I'm just tossing this out there for a possible check.

In my case the car ran fine but would pop or shudder ocasionally for a second then clear up and run fine.
I had it checked for codes.....nothing. The issue became more frequent over several months to the point of dieing from time to time. One day I notice the speedo would drop to the bottom when this happened.

Since there were no codes and the speedo was dropping I gambled and replaced the speed sensor that plugs into the transmission.

The speed sensor did the trick, no more popping or dieing.

This is just an idea, I'm far from being an authority.

Good luck,
Gregg

 

Check this out:

https://www.cherokeeforum.com/f2/nee...89/#post428761

 

Just a partial update on previous.. while waiting on parts, I pulled off the distributor cap, (which I'm ashamed to admit I didn't bother with since almost a year ago when I bought it - ran so well there seemed no need) and it was evident that there were problems there. Not the usual pitting or deposits, rotor and cap showing damage. Seems that distributor shaft bearings or other issues cause a condition where you get lateral movement of the shaft. Not good. But, it explains why I was getting intermittent problems on bumps and uphill/downhill. The computer sets and can compensate to some extent for timing but in an extreme case where the distributor is faulty it just can't. Still haven't fixed it, new dist comes in tomorrow, so I will only know for sure then. I will try it with new dist with Mopar crankshaft sensor, rotor, and cap. Also have new TPS and CPS here, but if it was the distributor, I can wait on replacing those. Just mentioning this as many are looking at sensors as I did, but it pays to check for slop (lateral movement - looseness) in the distributor shaft. There are a couple of videos on You Tube that show it.

 

Update, after changing to a reman distributor, new cap, rotor and Camshaft position sensor, (all Mopar except for dist) no fix for the basic issue. It started great and ran at idle just fine, put it in gear and died. Hard to restart and same missing. Although dist and all needed to be changed, this apparently was not the cause. Next to the CPS I have here on deck. Also will be looking at PCM TCM and related connections due to code P1694 and will verify that code is still occurring. Found a procedure here to follow.

 

Update for me:
the CPS wires were melted on the exhaust. CPS replaced. Let's hope that fixes it (won't know for sure until I've been driving a week or so).

Also, I'll have to see if the transmission codes come back.

 

Just to go full circle, changing the crankshaft position sensor got my codes 0700, 1694 cleared. In the process, I did fix a few other things that needed doing, distributor, cap, camshaft sensor and gapping the plugs that looked really good considering the engine has 155K+. In hindsight, I could have done the NSS first as I did notice reverse lights were not going on without playing with the shifter a bit. Even after the CPS was changed it still stalled when putting it in drive. Pulling the NSS and doing the cleaning made a big difference. Odd thing was, even though it cranked and started in Park and Neutral, the contacts were gunked up and one looked like it was pushed down too far in the recess. The NSS does send shifter position to the PCM which passes that on to the TCM as I understand it. I'm not clear on exactly what the system does with that info but it appears to me now that it's important to how it runs as much as cranking the starter and running the reverse lights.
Runs great again, and now I can get more enthused with doing other work on the XJ.