Hey guys Im new here and have a 1990 jeep cherokee 4.0L I6. When I am at highway speeds and then slow down to take an off ramp, my idle drops to 0 and dies. I tried replacing the idler control valve and that didnt help at all. I am considering replacing the EGR as it feels faulty (the diaphragm does not budge). Any ideas??? Also, while just sitting and idling, it idels around 400 to 500 rpm. I would like it to be around 600 to 700 rpm. Any help would be appreciated!

 

Sounds like your throttle positioning sensor is bad. Its on the throttle body. Mine did the same thing.

 

ya x2 on the tps!

 

Would it maybe be your idler pulley? Have you checked that to make sure when you rapidly deccelerate that your idle belt doesnt catch or something? This might cause your idle rpm to just drop and die

 

Try cleanning your idle air solinod,that controlls your idle not the tps,if it is closed no air will pass to let it idle.My tps was bad but it still idled ok,and without dieing.

 

my xj doesn't idle that low but when she starts cold it jumps from around five hundred to about 1200 RPM would it be the same case for me as well?

 

Must be nice cuz mine didnt. The rpms would go to 0 and die. Besides he already replaced the idol sensor.

 

but is it working,have you cleand the TB. Mine was dirty and after cleanning it idle up too high becouse the po adjusted the wrong thing.

 

vaccum line clogged, broken, leaking
or CPS

good luck and let me know!

 

Thanks guys. Yeah I've tried replacing the idle control valve, it didnt work, so I just cleaned the old one and took the new one back. I will look into the tps. Have you guys heard of the EGR effecting the idle?

 

Oh and Mulisha, how do I check the vaccum lines besides visually?

 

noob question but what all vaccum lines would i have to check...
because i know there is a rubber line that leads from the center of the valve cover that tracks to the intake box,, and a steel line towards the fire wall that leads to around the same place as well not too sure on the steel line towards the back of the valve cover.. both very easy to pop off w/o any tools

 

The TPS does control the idling cause mine would start and then die unless i help my foot on the skinny pedal so i took my throttle body off and cleaned my TPS and.. Good as new

 

Ok maybe on later 4.0s the tps. Is inside the TB, but on the older ones the tps is on the outside of the TB.When the tps is adjusted right it only touches and starts to move after the throttle plate start to open.I wonder though mine faild and was only giving .2 volts,if one fails on the hi side say closer to 5 volts if that would change things.

 

Thanks for all the replys. I did the following. Removed the trottle body and EGR and cleaned. Then looked for vacuum leaks. Found one vacuum line that was not attached to anything. Plugged it and now my idle is much much better. It is a little high sometimes, but I'm sure just plugging the line wont be a permanent fix. Thanks guys!