4.0L gurus' help please

[born2jeep]

I have a 98 tj with an auto, and im having idle issues. The jeep starts alright most of the time and stays at about 750rpm, but after I drive it, and come to a stop, it revs at about 200-350rpm. Even after i put it in park, most of the time the idle wont go up. Unless the engine is 100% warmed up, when coming to a stop, I sometimes have to gas it to keep it running.

The check engine light is on, so I took it to auto value to read the codes and it said:

p0505 Idle control system.
-a shorted or open condition detected in one or more of the air idle control motor circuits.

Now I wasn't quite sure what to think of this, but I have fixed idle problems on other jeeps by replacing the TPS. So rather then buying one, I borrowed a friends throttle body with all the sensors(it has been sitting for about 3 months, but worked fine before that), and swapped it onto mine. I disconnected the battery for a minute, then gave it a shot. I am still having the problem.

Does anyone have any ideas?

Sam

[XJHERO]

maybe o2 sensor

[cablesmurf]

maybe o2 sensor

I borrowed a friends throttle body with all the sensors

O2 sensor should have been on the the new TB...

Darn XJ guys don't know how to read...

[BlackYJ]

The IAC motor may run off of vacuum, but i can't remember.  I would check all the wires going to the IAC and see if you have any vacuum leaks on the intake or something, maybe  :?

[XJHERO]

XJHERO wrote:
maybe o2 sensor


Quote:
I borrowed a friends throttle body with all the sensors


O2 sensor should have been on the the new TB...

Darn XJ guys don't know how to read...

My O2  sensor  screws into my exhost pipe witch is not attached to theTB

[born2jeep]

The IAC motor may run off of vacuum, but i can't remember.  I would check all the wires going to the IAC and see if you have any vacuum leaks on the intake or something, maybe  :?

I just replace the intake and exaust manifolds. I was thinking that about the intake as well, thats why I swapped it. And also it looks like some body has already checked some wiring, because lots of it is out of the casing. Do you think that it could possibly be the ECU?

I will change the o2 sensor on the exaust tonight, and see if that changes anything.

[cablesmurf]

XJHERO wrote:
maybe o2 sensor


Quote:
I borrowed a friends throttle body with all the sensors


O2 sensor should have been on the the new TB...

Darn XJ guys don't know how to read...

My O2  sensor  screws into my exhost pipe witch is not attached to theTB

Ack! Man, sometimes I speak before I think. Don't worry about me...I'm new. :oops:  :oops:  :oops:  :oops:  :oops:

I was tinking IAC.

[XJHERO]

XJHERO wrote:
maybe o2 sensor


Quote:
I borrowed a friends throttle body with all the sensors


O2 sensor should have been on the the new TB...

Darn XJ guys don't know how to read...

My O2  sensor  screws into my exhost pipe witch is not attached to theTB

Ack! Man, sometimes I speak before I think. Don't worry about me...I'm new. :oops:  :oops:  :oops:  :oops:  :oops:

I was tinking IAC.

 

[streetvan1]

Ok, here's my 2 cents. Hopefully there was an IAC motor on the known good throttle body you put on there. If so, you can rule that out.

The next step is to check for vacum leaks. The code indicated a cirtuit fault, but sometimes code defenitions can be confusing. Check for vacum leaks, because there's a chance that the code means that the IAC circuit is not opertaing in range. the IAC will run in a more closed position than normal if it is compensating for a vacum leak.

If there are no vacum leaks, then you need to check your IAC circuits before you go and replace the PCM. This is easy, the wires should be the same color on the IAC motor and on the PCM. Use an Ohmmeter to check the restistance of each wire. If you've ruled out the IAC actuator, and the circuits, then you have a PCM fault. If the wires are out of their tubing, there's a fairly solid chance that there's a wiring fault.

[cablesmurf]

If you are in need of a new PCM, I think Lemonaid Jay has one for sale.