Hi, I have a 2000 Jeep Cherokee Sport 4.0 liter. It has a new exciting problem. It now likes to stall at random.... So here are the details. 1 out of 25 times I go to start it cold. It will act like it started, but not so much. The fuel pump will make noise and the electric fan will run but the engine is not running. I can crank the engine until the cows come home and it will not start. If I turn the key back to the off position and try to start again, it will fire up like nothing is wrong... This was the extent of the problem until today. I was driving down the road at about 35 mph.. when the engine decided to turn off... I pulled over and tried to restart the engine without turning the key to the off position and it just cranked. As soon as I turned the key to the off position and tried to start it fired up without a problem... This happen two more times on my way home even once at 60mph on the freeway.... So when I got home I checked out the engine compartment. I did find a disconnected vacuum line which I reconnected (Vacuum line going to the manifold). Reconnecting the vacuum line lowered my idle so now my volts drop to zero when I turn on the headlights and run the heater at level 2 when I am stopped. (NOTE: The idle is not rough)I am now idling around 500 rpms... Not sure if this is good or not... So I cleaned out the IAC .. per other threads on idle issues... didn't help.. and it stalled once again per my earlier comments.. Other pertinent information

1. Alternator is brand new
2. Battery is brand new

If anyone can help ... It would be greatly appreciate.. Thank you in advance for any help..

Thanks!
-Markjp

 

do a fuel pressure test man.

 

(*)

 

Here is an update. I checked the fuel pressure. With the ignition turned to the on position I get 45 psi. When I start the engine to let it idle I get between 45 and 51. (Needle bounces back and forth. I guess this is common for return-less systems). On the leak down test. I didn't lose any pressure at all after 15 minutes of waiting.

Additional information.. This morning with the engine cold it was very difficult to start. I had to push the gas pedal to get it to start. (This is the first time I tried to start cold after reattaching the vacuum hose.) I noticed if I pull any vacuum line it would actually start easier. Doesn't seem to be getting enough air? The check engine light did come on, but I can't check the code since every time I use a code scanner it gives me a no bus error on the odometer... and the scanner cant find the computer.. Checked all the pins on the plug under the dash and they seem fine....


I appreciate the help so far... any additional help or thoughts is appreciated.


Thanks!
Mark jp

 

I now replaced the Throttle Position Sensor. The check engine light has gone away and the idle runs around 700 RPMs. But it is still hard to start when it is cold. I have to hold the gas pedal to get it to start. When it is warm it starts right up.. Could this be the temperature sensor?

 

What you can try is the following.
On your next cold start, prime the fuel pump first:
Turn key to ON (dont start the engine) and wait 4-5 seconds (you should hear the fuel pump prime in the back), turn key to OFF and repeat this two more times and then start your engine.
If your startup is significantly faster with this 'poor man's prime' , is could be either your fuel pump, or the check valves (one in the fuelpump, one somewhere else) loosing pressure, or better said not holding pressure. I know you got decent pressures with engine running, but this is worth a try.
If the above is showing difference in startup, we'll talk about how to pinpoint it down further.
Let us know how you go.

One other thing which is always on the list in 4.0 's with random stalling and cutting out , especially if its not been replaced in the past: the CPS.

 

Hi, thanks for the advice. I tried the "Poor man's prime". It didn't seem to have any affect. It would just continue to crank. When it is cranking without the pedal push, it almost wants to start, it just doesn't seem to catch. As long as I hold the pedal it will start right up. Could this be the Crank Position Sensor?

 

Is your temperature gauge working properly? I had the same problem, what caused it was the ECT sensor connector was loose and not making good contact. This made it very hard to start when it was cold. I probably would have spent a long time trying to pinpoint that, but I noticed that my temperature gauge was not working so I investigated that. Coincidences are very rare when it comes to cars.. I had to clean and tweak the pins to finally get good contact, but once I did that it does cold starts without issue. Why the Jeep refuses to cold start with the ECT unplugged, I have no idea.

Edit: This was on my '97
another thing you said that kinda triggered my memory, is that it would try to catch, and then just crank. Mine also did that.
The ECT sensor won't cause your engine to stall out while driving though. Unless it somehow shorted out and suddenly sent a false overheat signal to the PCM, but I havent had heard of that ever happening to anyone. kinda farfetched. Your stalling issue is almost definitely caused by something else. The difficult cold start definitely could be the ECT though.

 

I also have a 2001 Cherokee that has been doing something similar....I have replaced the plugs, boots, coil pack, map sensor, evap purge sensor, and wrapped my fuel injectors in heat tape (thought the rough idle and stalling was do to the common heat soak). I have checked for vacuum leaks in every way other than a smoke test. Im running out ideas here. Once I get the money I will be replacing the cps and the cts. ill keep checking back here and see if you have made any progress......

anyone with ideas?

 

Check you IAC Idel Air Control. It's the plunger thing in the T body. If they fail or get gummed up they can cause cold start issues. My old 96 GC with a 318 in it used to need the IAC cleaned once every fall when it would start to get cold out.

 

I cleaned my IAC and no change.....might help this guy though.

Another thing I forgot to mention is mine will start and run decent it when im driving particularly when once I get around 30 mph it bogs down. When I push on the gas it starts to seem like its dying.

 

Thanks for the advice. I did check the IAC. I pulled it out and cleaned it but unfortunately it did not change anything. I haven't checked the ETC. My temperature gage appears to be operating properly ,but I'll have to give it a look. I haven't had any stalling problems recently, not that it is fixed, just doesn't seem to be stalling at the moment. I'll check the ETC and CPS and see where that gets me..

 

CPS first. I already said this.
If your CPS hasnt been changed out before, you still have the original and it will fail at some point in the 4.0...

 

On the stalling at 30 mph thing, my 96 ZJ was doing that, and dying at stop lights - starting right back up. Mostly before reaching 195 degree operating temperature. Mine was (I think) bad connections in the PCM, which I resoldered two weeks ago today and have not had any more issues. Try starting it in park and wiggling the conenctors to the PCM. If it stutters or stalls, that could be the (or, "an") issue. The fix was not bad, took maybe an hour.

 

Hello All,
I would like to thank everyone for their support on trying to help me with my Jeep issue.... Unfortunately I have to say my Jeep was stolen this evening. So I won't be able to give you final feedback on the CPS or the Temp sensor...... I did take it in before it was stolen to have it checked out by a shop to see if they had a opinion on the issue. The thought it might be the Transmission sensor related. something under the dash? They recommended that I bring it to Jeep and have them look at it. Which I planned to do tomorrow. But walking out after work my jeep was gone....... Some one else now has my jeep! So anyways, that is all I have. My Jeep was awesome despite the minor problems, very frustrating as it is worth more then insurance will give me but Que Sera, Sera..... Thanks All!




-Update.. Jeep was recovered..... and repaired. The issue was the oxygen sensor. Replacing the O2 sensor fixed everything . Runs great now...