Well, I've replaced the fuel filter, checked the fuel rail for pressure(it's ok), clean the throttle body, tried bypassing the ceramic noise supression element and just replaced the CPS. The car will start and then runs really rough and dies. Anyone have any other ideas?

I need help desperately !

sounds like you IAC (Idle Air Control) valve is bad or may need cleaning.

sounds like you IAC (Idle Air Control) valve is bad or may need cleaning.
OK, where is this located? Can it just be cleaned?

Not exactl sure about on the XJ's, but it should be located on the THROTTLE BODY, it has a 4 wire electrical connector connected to it.

Most of the time the shaft just needs to be cleaned along with port on the throttle body in which it corresponds to.

Not exactl sure about on the XJ's, but it should be located on the THROTTLE BODY, it has a 4 wire electrical connector connected to it.

Most of the time the shaft just needs to be cleaned along with port on the throttle body in which it corresponds to.
OK, Thanks. I'll try this tonight. :smile:

OK, Thanks. I'll try this tonight. :smile:
Tried cleaning the TPS and cleaned the throttle body also. Just replaced the CPS and the car will start, run rough and then stall like it's not getting fuel. This is driving me crazy....It's gotta be a bad sensor but which one? :screwy:

Did you clean the Idle Air Control Valve?
if you cleaned it and it is still stalling, then it will need to be replaced.

Remember, before removing/replacing any electrcal component, to disconnect the negative battery cable.

Did you clean the Idle Air Control Valve?
if you cleaned it and it is still stalling, then it will need to be replaced.

Remember, before removing/replacing any electrcal component, to disconnect the negative battery cable.
OK, I'll stop at the parts store to see if I can get one. Hopefully it's not expensive. I am replacing a lot of parts with no luch so far but that may be it. That's the valve on the front of the Throttle Body? I spryed it with carb cleaner and moved it with my fingers to see that it moved but it may be bad.

I am not exactly sure of the location on your cherokee, but it is on the throttle body and it should be the only electrical component on the throttle body with 4 wires coming off of it.

I am not exactly sure of the location on your cherokee, but it is on the throttle body and it should be the only electrical component on the throttle body with 4 wires coming off of it.
I will remove it totally and then clean it again and if that doesn't work, I will replace it. I hope this works. Thanks for the advise.

I will remove it totally and then clean it again and if that doesn't work, I will replace it. I hope this works. Thanks for the advise.
OK, I ended up replacing the TPS and the car starts, runs longer now but runs really rough and when it idles, it dies still.....Ehhhhhh !
Any other ideas?
Thanks

Maybe a bad o2 sensor? Maybe one of the jets is clogged, maybe a bad spark plug wire, and it is only running on 5 cylinders? That really sounds like a fuel pump problem, but if psi is around 40 you should be okay.

Well, I've replaced the fuel filter, checked the fuel rail for pressure(it's ok), clean the throttle body, tried bypassing the ceramic noise supression element and just replaced the CPS. The car will start and then runs really rough and dies. Anyone have any other ideas?

I need help desperately !
Check the fuel pressure regulator. I had this problem on my buick century and I replaced it for about $60.00.

Check the fuel pressure regulator. I had this problem on my buick century and I replaced it for about $60.00.
Any idea where the fuel pressure regulator is located?

Maybe a bad o2 sensor? Maybe one of the jets is clogged, maybe a bad spark plug wire, and it is only running on 5 cylinders? That really sounds like a fuel pump problem, but if psi is around 40 you should be okay.
Yeah, it sounds like a fuel pump problem to me also but that seems to check out ok. The pressure is where it should be at the fuel rail.
Go figure...
I may just change the plugs to see if that will help. It's funny but it almost seems like maybe when I let off of the key after the engine turns over, that the signal may be broken off. Maybe the ignition is my problem. I don't know.

if you keep the key in the start posisition, will it stay running?

check this thread in the cherokee section, maybe you have the same problem.
http://www.automotiveforums.com/vbulletin/showthread.php?t=470684

if you keep the key in the start posisition, will it stay running?
No, the car does not keep running. I changed the plugs and it run smoother but stalls quickly. ALmost like it is not getting fuel but I checked the fuel pressure at the rail and it was ok. Maybe when it starts, it can't keep the pressure up. Is that possible? Any idea on how to check that? Thanks

check this thread in the cherokee section, maybe you have the same problem.
http://www.automotiveforums.com/vbulletin/showthread.php?t=470684
Thanks, I'll check this site out...
I am desperate. Need to get this fixed before it gets cold ! :banghead:

How much pressure do you have when the vehicle is started? You need at least 40 psi when your turn key to on position

How much pressure do you have when the vehicle is started? You need at least 40 psi when your turn key to on position
I have the 40 psi when I start it. I don't know if it keeps the pressure up though. I hear the fuel pump running when I turn the key and then it stops. I then start it and it runs for a few seconds and then drops off and tries to run again and then dies down and stalls.
Any idea?

check this thread in the cherokee section, maybe you have the same problem.
http://www.automotiveforums.com/vbulletin/showthread.php?t=470684
Thanks. this gave me some good ideas. Problem did sound simular.

Thanks. this gave me some good ideas. Problem did sound simular.
Well, I tried bypassing the ceramic block with no luck, I also swapped out the relay. The car starts, revs to about 2000 rpms and then drops to 0 and revs up again and then down to 0 and then stalls.
Not sure where to go from here. Any idea?

hummm, still sounds like a bad IAC valve.

have you checked the map sensor yet? Did it rev up to 2000 rpm before you swapped the relays?

will it keep running if you hold the gas pedal down?

have you checked the map sensor yet? Did it rev up to 2000 rpm before you swapped the relays?
What is the MAP sensor? Yes, it did rev up before I changed the relay but I changed the plugs and now it does the same thing but runs smoother. The plugs were a bit fouled from the way it is running now.

will it keep running if you hold the gas pedal down?
No, it won't keep running if I keep the pedal down. It's like it stops getting fuel and then gets it and revs and then drops again.

hummm, still sounds like a bad IAC valve.
What is a IAC valve and where is it? I will check it or replace it.
Thanks

hummm, still sounds like a bad IAC valve.
:banghead:

the Idle Air Control Valve is located on the Throttle Body it should have a 4-wire electrical connector connected to it. The should be 3 sensor, MAP, TPS, and IAC, the IAC is the only one with 4 wires going to it.

the Idle Air Control Valve is located on the Throttle Body it should have a 4-wire electrical connector connected to it. The should be 3 sensor, MAP, TPS, and IAC, the IAC is the only one with 4 wires going to it.
OK, I took this apart and cleaned it with no avail so I guess I will have to replace it and try again. I also cleaned the throttle body very well while I had it apart.

I tried unplugging my iac on my 89 cherokee just to see what would happen. When I started it up the rpm went to about 2800 and stayed there.

I tried unplugging my iac on my 89 cherokee just to see what would happen. When I started it up the rpm went to about 2800 and stayed there.
Thanks, that's a good sign for me. I will see if I can get a new one to replace the one I have. I think they cost about $40.00 or so.
Wish me luck ! :)

Thanks, that's a good sign for me. I will see if I can get a new one to replace the one I have. I think they cost about $40.00 or so.
Wish me luck ! :)
Well, I replaced the part but it still starts, runs at a high idle and then stalls. I am running out of ideas with this one. Her's a crazy question, do you think it could be a very bad tank of gas that's causing the problem?
I tried to siphon it out but oculd not get the tub down the tank neck all the way. I was thinking about disconnecting the gas line at the fuel filter and letting the fuel pump empty it out. What do you think?
I hear the fuel pump every time that I turn the key on as it gets up to pressure so I don't think it is that. I also measure the pressure in the fuel rail and it was up to par. What else could this be?
Thanks for your help.

the Idle Air Control Valve is located on the Throttle Body it should have a 4-wire electrical connector connected to it. The should be 3 sensor, MAP, TPS, and IAC, the IAC is the only one with 4 wires going to it.
Thanks, I replaced the IAC but it still has the same problem. It starts, runs at a high idle (approx. 2000) then stalls. Any other ideas?

whave you tried to start the jeep and hold the gas pedal down? Does it still stall if you do that?

whave you tried to start the jeep and hold the gas pedal down? Does it still stall if you do that?
Yes, it just starts, revs up to about 2000 rpm and then drops down to 0 and revs up again, drops down to 0, revs up again then drops and then dies. I can hold the pedal down or not, doesn't matter.
Could the gas be bad? It has 3/4 of a tank in it.

the irratic idling (up and down) can be caused by a bad Throttle Position Sensor (TPS) but I have never seen/heard of a bad TPS causing stalling.

the irratic idling (up and down) can be caused by a bad Throttle Position Sensor (TPS) but I have never seen/heard of a bad TPS causing stalling.
I already replaced the TPS, it didn't make a difference....I also replaced the CPS, no difference.....I am running out of things to replace here

hummm, When you replaced all these things did you Disconnect the battery?

I guess the only thing next would be to get a fuel pressure readng with the jeep running to see if the pressure is constant.

hummm, When you replaced all these things did you Disconnect the battery?

I guess the only thing next would be to get a fuel pressure readng with the jeep running to see if the pressure is constant.
I checked the fuel pressure without it running at the rail and it was 32 lbs or there about....I can't check it when it is running because it doesn't stay running long enough.
I didn't disconnect the battery when I replaced the sensors, do I need to do that to reset them somehow? I didn't know I needed to do that.
Oops... SHould I try to disconnect it an reconnect it? Will that help?

I checked the fuel pressure without it running at the rail and it was 32 lbs or there about....I can't check it when it is running because it doesn't stay running long enough.
I didn't disconnect the battery when I replaced the sensors, do I need to do that to reset them somehow? I didn't know I needed to do that.
Oops... SHould I try to disconnect it an reconnect it? Will that help?

Well Disconnecting the battery now will not help. The was a post on here about someone who did this same thing, they finally took it to the dealership and they said the computer needed to be re-initialized b/c she forgot to disconnect the battery b4 removing/replacing the component.

I had a problem like this in my 94 ZJ about a year ago when I replaced my IAC Valve, I replaced it and it didn't help it stalled again so I was like OK I got a bad part from autozone, so I took it back and when I replaced the new one I remember I didn't disconnect the battery when doing the first one, so I disconnected the battery and replaced the part and it's been fine ever since. I'm not sure if it was a bad part or the battery disconnect was the problem exactly but it worked afterwards.


So there are 2 things you can do, replace the components again (most of the time the electrical parts hold a 90 day warranty) remembering to disconnect the battery or take it to the dealership and they can check the computer to see if it needs reinitialized which who knows how much that will cost.

Well Disconnecting the battery now will not help. The was a post on here about someone who did this same thing, they finally took it to the dealership and they said the computer needed to be re-initialized b/c she forgot to disconnect the battery b4 removing/replacing the component.

I had a problem like this in my 94 ZJ about a year ago when I replaced my IAC Valve, I replaced it and it didn't help it stalled again so I was like OK I got a bad part from autozone, so I took it back and when I replaced the new one I remember I didn't disconnect the battery when doing the first one, so I disconnected the battery and replaced the part and it's been fine ever since. I'm not sure if it was a bad part or the battery disconnect was the problem exactly but it worked afterwards.


So there are 2 things you can do, replace the components again (most of the time the electrical parts hold a 90 day warranty) remembering to disconnect the battery or take it to the dealership and they can check the computer to see if it needs reinitialized which who knows how much that will cost.
Thanks for the advice. I wonder what they do to "reinitialize" the computer? I have a friend that is a mechanic, I'll ask him if this is something that I can do. Maybe the part is bad, I did but it from AutoZone..who knows....this problem is a real pain, nothing seems to work.

Thanks for the advice. I wonder what they do to "reinitialize" the computer? I have a friend that is a mechanic, I'll ask him if this is something that I can do. Maybe the part is bad, I did but it from AutoZone..who knows....this problem is a real pain, nothing seems to work.
Well, I disconnected the battery for about 4 days and then hooked it back up again. The car started and would actually idle now. As soon as you touch the gas paedal, it wants to stall. Since it was idleing I went and disconnected the TPS and it kept idling, I hooked it back up and then disconnected the Air sensor (IAC?) and it still kept running. I out that back on and disconneted the CPS and it stalled, so I guess that is working also. Still don't know what the problem is. What do you think?
Oh, the capacitor for the fuel pump was clicking away as it should have been. Don't know where to go from here though...hmmmmm.....