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Bad Gas or Fuel Pump or IAC

D

danny Benavidez

NAXJA Forum User
Location
Texas
Just today My 2001 XJ started dying at idle.

This morning I started up my Jeep and then went back into the house to find some paperwork I needed. I left my Jeep idling for over 10 minutes came back outside and it was running OK. So later today I got some gas about 1/2 tank ,then the problem started. The Jeep runs fine at high speeds but at a stop light when the engine idles down to 500 rpm's it keeps idling all the way down to 0 rpm's and it now does this everytime I stop moving! Before I came home I added some more gas, premium grade, 1/4 tank. Maybe it will offset the bad gas. But does this sound like poor gas or is it something else? Like the fuel pump or the Idle Air Control? The check engine light is not coming on. :dunno:
 
Running smooth but just at a low idle?
 
Ok, not heat soak.

I would go after the TB and IAC, clean them thoroughly and see what happens.
 
joe_peters said:
Ok, not heat soak.

I would go after the TB and IAC, clean them thoroughly
Click to expand...

I did clean TB & IAC last week and tomorrow morning I'm changing the spark plugs it's been on my to-do list for weeks and tomorrow I'll have time.

The weather here in mid Texas today it was been 104 degrees.
I has thinking Heat Soak too but with heat soak I do get some hesitating but does not always stop running
 
Last edited:
Another thing to consider is the E15 and reformulated fuels.

Ethanol doesn't like heat, and just causes driveability problems in general.

My 1990 owner's manual says using 10/90 ethanol/gasoline mix is OK, but you may experience loss of MPG, and starting/driveability issues. If you do, they recommend usings unleaded fuel without alcohol--not with the EPA running things!!
 
I already run two tanks of fuel, And the problem has not gone away !
But I did adjusted the set screw on the throttle body. I opened up the butterfly valve a little just so I can see light around the eages. This fix is keeping the engines from dying at low idle. And all seams OK. But is it normal for the butterfly valve to be open ? I'm thinking it's not normal . So I'm going to replace the IAC soon


setscrew.jpg
 
winterbeater said:
If it ran good before, and you had to open the throttle stop to make it idle, the IAC isn't working.
Click to expand...

x2, I'm with Winterbeater on this one. The "base Idle" screw should just keep the throttle plate from slamming fully closed, i.e., turn it out, then turn it in until the first perceptible movement of the throttle plate.

A proper functioning IAC provides the idle and transition circuits (carb speak), and should take care of things.

As asked earlier, what happens when you unplug the IAC??
 
R6TeXJ said:
If its the IAC what codes come up?
Click to expand...

P0505 (Idle Air Control Motor Circuits) but it doesn't "always" fail in way that triggers a check engine light.

To the orignal poster.....I'm with the others. think I'd try a new IAC. Cleaning it sometimes restores function if it is a carbon problem but if the unit is dead, no amount of cleaning will bring it back to life.
 
danny did this help I just had this happen to ,me today Jeep will run and as soon as i let off the gas it dies if I keep even lightest pressure on the gas pedal it will keep running
 
I'm seeing the same thing on my brothers '00. You have to give it a little gas to start it and if you let off the throttle it will die. If you keep on the gas it will run and eventually start running smooth again and be fine for a while. Anybody have any suggestions?
 
Muddy90XJ said:
I'm seeing the same thing on my brothers '00. You have to give it a little gas to start it and if you let off the throttle it will die. If you keep on the gas it will run and eventually start running smooth again and be fine for a while. Anybody have any suggestions?
Click to expand...

Three possibilities come to mind:

1. Throttle position sensor is suspect if you have to tip in the throttle to start. I would definitely test it.

2. Clean the idle air control and throttle body.

3. Be sure the battery is solid (load test it). If you have a marginal battery, it can be symptomatic right away and then get better as the alternator charges the battery up as it runs.
 
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