Kycheokee

Working on a 2000 4.0L. Sport. 84K miles.

I hate when I start throwing parts at a problem without a real insight to what the problem is but that is where I now find myself. A few days ago the heep starting "stumbling" while running. Not a miss but rather more like the engine was turned off and back on. There was not a pattern to it that I could tell. It became progressively worse as it became a true stall but would restart. It then quit one day and would not restart.

In reading here and other forums

Kycheokee

Working on a 2000 4.0L. Sport. 84K miles.

I hate when I start throwing parts at a problem without a real insight to what the problem is but that is where I now find myself. A few days ago the heep starting "stumbling" while running. Not a miss but rather more like the engine was turned off and back on. There was not a pattern to it that I could tell. It became progressively worse as it became a true stall but would restart. It then quit one day and would not restart. In reading here and other forums the crankshaft position sensor seem the likely suspect. Before it quit that I went to autozone to try to get a code but none were found.

I replaced the CKPS. with a factory sensor.

The truck ran better but would occasionally still have a stumble. Tonight it again quit and would not restart. My son went to AZ. and brought me a camshaft position sensor. Installed and at first no start but then it did and I managed to get home. In driving home. Same behavior and its is more pronounced at highway speeds. ( 55 +)

Suggestions ?

crawler487

When it stalls on the road and won't start, can you hear the fuel pump running when you turn the key to the on position? If it isn't running then you could have a bad pump or a bad ground/connection to the fuel pump.

Kycheokee

The pump "primes". Or comes to pressure and then stops. There has not been any change in its behavior.

freegdr

What codes are present ?

Kycheokee

No codes. Have checked three times now.

Bustedback

Fuel pressure, check it. Hearing the pump run does not guarantee good pressure.

Kycheokee

Well I know it has been a few days but I wanted to follow-up and let folks know where. I am.

First I want to thank everyone that has offered their advise.

I did check the fuel pressure at the rail and it was spot on 49#s.

I cleaned and reattached the 3 grounds in the engine compartment and cleaned and reattached the positive cable and also had the battery load tested. (It is less than 1 year old.

None of this cured my problem.

I took it to a shop I more or less trust and just received their diagnoses. The mechanic believes it is a bad instrument cluster. He said that if the ECM loses communication with the cluster it will stop running. They found the problem when while idling they saw ( I guess on a scope) the loss of communication. He said that it did not surprise him that the "stumble" or the intermittent non-start was intermittent. This was late in the day and I do not have a price quote but it does not sound cheap.

I welcome members thoughts and suggestions

Bustedback

If the cluster is giving you a "no bus" message it usually means there is a crank sensor problem.

Kycheokee

Thanks for the reply.

There are no codes nor any messages.

Kycheokee

Well my troubles continue. I pushed back to the mechanic about the need for a new instrument cluster. I received a call back today. The shop told me that they had continued testing and measuring voltage at the sensors on the truck. These were checking out as being ok.

He did say the stalling (its like the engine is turned off and then back on. Every instrument stops working. Still no codes) has become much worse

The mechanic feels that the he issue is either at the ECM or with the cluster. I have some questions I hope I can get answers to so I can verify what I am being told.

1. Assuming the purchase of a new ECM, to install it are there downloads or other programing that needs to be done before it can be used?

2. How year specific is an ECM? My XJ is a 2000 4.0 L. Is a 2000 the only ECM that will work or would I have some junkyard options. Also with the instrument cluster. Am I limited to only that year?

3. Does the instrument cluster have any sort of module or "chip" that the ECM must communicate with so the engine will run?

Thanks for any help, information, or advice that can be given.

HappyTrails

Symptoms also sound similar to bad Throttle Position Sensor. Should leave a code, though. But lets not make assumptions here. How many miles? When was the TPS last changed? If it has been a while, it's not a bad idea to throw that part at the problem. Easy to change and not a lot of money. And you will need to do it anyway sooner or later, so it's not a wasted effort.

Just some thoughts.

Been through lots of TPS's on my Mopars over the years.

Kycheokee

84,000 miles and as far as I know the TPS has never been changed. However I think it tested ok. I will double check with shop tomorrow.

Kycheokee

I realize now that I have been guilty of the most common complaint by regular members of this forum: not doing some simple web research before posting a question. After looking on the web it is obvious that the ECM is year specific, heck it appears to be almost VIN specific! And if I were to buy a new "raw" ECM from Jeep, there would indeed need to be downloads and programing to be done. Although I am not sure how that is done.

I still am unclear if there are circuits or modules in the gauge cluster that would be the cause of my problems.

I was reading post which seem similar to my issue. A veteran member posted a reply, which of course I can't find now which detailed all the symptoms of a failed crank position sensor. The symptoms were all the same as mine until "no spark". I have a strong blue spark at the plugs. Also my new sensor is testing that it is ok. (A factory part)

I think I have decided to replace the computer.

There were many options of rebuilders. Does anyone have experience with a particular company or have a recomendation?

Thanks for any help or advice!

NMJeep01

Just first thing to remember if the CPS has no signal you wouldnt be getting spark or fuel, second thing the ECU is vin specific and also would need mileage, ive had an issue that was very similar and ended up being the ECU although i wouldn't jump the gun on it, check relays and spark plugs to begin with, then check fuel and spark, dash is possible although not that probable, the dashes are pretty much interchangeable only depending on if the guage cluster replacement has the same lights/ guages, for example some came with RPM guage others have no RPM indication, if gauge visually looks the same then it is, make sure all sensors read out fine, if all else fails its a good chance of the ECU, the year, and type of transmission (m or a) will change the ECU, the dealer should be able to give you your ECU model # normally the last two letters at the end of it wont change functionality, Ebay is a great place for the ECU and to check interchangeability, if you want to see when i experienced a similar problem look at my threads and hopefully will give you a good idea, i hope this helps, just PM me if you have any questions ill try to help my best