Idle Issue

[Engir]

Some of this is going to sound strange I think. After I replace the brake booster and took away the air leak the high idle stopped working. My 4.0 1987 XJ will not idle at all on start up and when it is warmed up and I take my foot off the pedal it goes to an idle of about 500 RPMs on the tach and will eventually die. I know my pump is not holding pressure, the sending unit is bad also, I have a new one but no way to get the gas out of the tank to change it (I am in Costa Rica) I have looked over the throatle body and I do not see any where to set the high idle and idle can someone help I know there has to be a place to do this I cannot find it, please and thank you.

PS, there are no vacuum leaks, I have done a visual and audio inspection of the engine.

 

[superj]

your idle control valve And its area of the throttle body are clean?

 

[Engir]

your idle control valve And its area of the throttle body are clean?

Yes, I sprayed the throttle body down with carb cleaner about a week ago thinking it would help with the issue and it did nothing.

 

[superj]

maybe your idle control valve is no good anymore?

the pump holding pressure, do you mean its not putting out the required pressure for running or it bleeds down after you shut the truck off?

if it bleeds down after shutting off, that won't effect the running issue but you can buy little in-line check valves and put it in the fuel line form the pump to the fuel injectors and it will stop the fuel from draining back.

inline fuel check valve - Google Search

i had to use one on a bmw that kept losing pressure when turned off. i didn't want to pay 150 bucks for a new pump when it was just the built in check valve that had stopped working. i put that right at the line where it connects to the fuel pump and the car went back to starting like normal

 

[Engir]

maybe your idle control valve is no good anymore?

the pump holding pressure, do you mean its not putting out the required pressure for running or it bleeds down after you shut the truck off?

if it bleeds down after shutting off, that won't effect the running issue but you can buy little in-line check valves and put it in the fuel line form the pump to the fuel injectors and it will stop the fuel from draining back.

inline fuel check valve - Google Search

i had to use one on a bmw that kept losing pressure when turned off. i didn't want to pay 150 bucks for a new pump when it was just the built in check valve that had stopped working. i put that right at the line where it connects to the fuel pump and the car went back to starting like normal

I watched some videos on YT and checked the pressure on the fuel rail there is a valve to dump the fuel if you are disassembling and there was no fuel in the rail the video said this is because the pump is bleed back, not holding pressure also the sending unit is not working I ran a check on the wiring using a multi-meter and determined that the sending unit is bad so I bought new unit on Amazon some months ago I only need to fuel level down so I can pull it from the tank without fuel going everywhere. Also on start up each time I can here the pump running and have to wait until it stops for the motor to start so it is bad bleeding back from lack of pressure.

 

[Engir]

maybe your idle control valve is no good anymore?

the pump holding pressure, do you mean its not putting out the required pressure for running or it bleeds down after you shut the truck off?

if it bleeds down after shutting off, that won't effect the running issue but you can buy little in-line check valves and put it in the fuel line form the pump to the fuel injectors and it will stop the fuel from draining back.

inline fuel check valve - Google Search

i had to use one on a bmw that kept losing pressure when turned off. i didn't want to pay 150 bucks for a new pump when it was just the built in check valve that had stopped working. i put that right at the line where it connects to the fuel pump and the car went back to starting like normal

Where is the idle control valve and how to test it?

 

[Engir]

I believe the one on the left is the idle control valve can someone tell me how to test this please?

I do not know what the one on the right is?

Thanks

 

[superj]

Is the other the throttle position sensor?

Its been a while since i had my renix cherokee. The good thing about the old renix fuel injection in your jeep is its very easy to trouble shoot using just a multimeter.

 

[Engir]

Is the other the throttle position sensor?

Its been a while since i had my renix cherokee. The good thing about the old renix fuel injection in your jeep is its very easy to trouble shoot using just a multimeter.

I have no idea what the other one is I am not 100% sure the one on the left is the idle control valve, I know one of them is? I also am still looking for a way to test it if there is one?

 

[superj]

if you can find a download of the factory service manual, it will give good instructions for how to check that stuff. i probably have a cd version of the 87 cherokee manual somewhere but i know i will forget to look for it when i get home.


i did find this though, on another forum

"The diagrams from the FSM show this:

So it looks like you could check for continuity across the pair of pins on the IAC.

This is at the ecu. It doesn't show what might be power vs ground.

 

[superj]

it says that the idle control valve is hard to test because it is a stepper motor and the ecu just tells it to open/close at a super high rate. it says the ecu won't even know if you icv is bad because it gets no info from the part and keeps trying to adjust the idle even when the icv is bad.

but, what i read is that if you try and clean it to roughly, it can cause the icv to fail and your idle will be erratic and very low, around 500

 

[Engir]

it says that the idle control valve is hard to test because it is a stepper motor and the ecu just tells it to open/close at a super high rate. it says the ecu won't even know if you icv is bad because it gets no info from the part and keeps trying to adjust the idle even when the icv is bad.

but, what i read is that if you try and clean it to roughly, it can cause the icv to fail and your idle will be erratic and very low, around 500

So reading this, this is what I got is when I pull the wiring connector there are two pins and I can check continuity with with my multimeter using those pins?

I watched a video yesterday on YT where a guy tried cleaning his because of blowby getting back into the throttle body from the valve cover, he was able to open and close solenoid with his fingers also. When it did not work he bought a new Idle solenoid that he said kind of helped and on that new one he could not open the solenoid with his fingers, meaning the old one was worn out. So from this information and my belief that the one on my Jeep is original I should pull the wires check for continuity and then see if how easy it is to open the solenoid with my fingers to see how worn the part is and then replace it and/or find a short, does that sound accurate?

Additionally if that other solenoid in my image is the throttle position sensor, I have not confirmed that at this point, I should check continuity on the wiring which I do not know how to do that yet and either way would probably be good to replace it also?

So later today I will start researching what the other solenoid is and how to check continuity, if you can help with that would appreciate

Thank you

 

[Engir]

I have comfirmed the other is the throttle position and that is not the issue the Jeep does not show any characteristics associated.

 

[Engir]

The wires going to the idle control solenoid is not two pins it is four. I am sure the issue is the solenoid itself and have ordered one on Amazon but would like to check for power and continuity can someone tell me how to check continuity and do I need to do all the wires or only one?

Thanks

 

[superj]

one should be a ground, the others, i don't know

 

[JPNinPA]

What fuel pressure are you reading? At key on, idle , 2000rpm snd 3500 rpm?

When you start do you need to hold the pedal or it dies?

This may be the IAC or the TPS. If the PCM doesn’t know the TPS is low or no pedal then it doesn’t know to regulate the IAC.
You could verify the TPS connection. Or read resistance closed to open. Many have blown dirt out of the TpS to regain function or worked the trottle valve open to closed several times.

Or the IAC is dirty or stuck.

Cleaning the IAC is not just spraying cleaner in the TB, but includes disassembling. Cleaning the TB side and the IAC plunger carefully. Then reassemble.

https://youtu.be/uSWJ1R6oP0U
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