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XJ Ask the Question Thread
::CF Moderator::
Joined: Aug 2011
Posts: 43,971
Likes: 1,578
From: Prescott, Az
Year: 1990
Model: Cherokee (XJ)
Engine: 4.0
Courtesy of TJWalker:
--------------------------------------------------------------------
The Idle Air Control (IAC) is mounted on the back of the throttle body. (front for 87-90) The valve controls the idle speed of the engine by controlling the amount of air flowing through the air control passage. It consists of a stepper motor that moves a pintle shaped plunger in and out of the air control passage. When the valve plunger is moved in, the air control passage flows more air which raises the idle speed. When the valve plunger is moved out, the air control passage flows less air which lowers the idle speed. Over time and miles, the IAC can get carboned up which can have an adverse affect on idle quality. Cleaning the IAC may restore proper function and is an easy procedure to perform and good preventive maintenance so it is never a bad idea.
CLEANING THE JEEP 4.0 IDLE AIR CONTROL
Remove the air filter cover, associated hoses and the rubber boot that goes from the air filter cover to the throttle body. Remove the IAC with a torx driver (2 bolts; one can be kind of hard to get to)
"Gently" wiggle out the IAC from the throttle body. Gasket on the IAC can be re-used if it is not damaged
Clean the IAC with a spray can of throttle body cleaner; inexpensive and available at any place that sells auto parts. Throttle body cleaner is recommended rather than carburetor cleaner as it is less harsh, safe for throttle body coatings and is best for this task. Use cleaner, a rag and a toothbrush and or Q-Tips. Be gentle; don’t twist or pull on the pintle that protrudes from the IAC as it is fragile and you could damage it.
Thoroughly spray clean and flush where the IAC seats in the throttle body with the same spray cleaner
It is also a good idea to clean the entire throttle body itself, the butterfly valve inside of the throttle body and all associated linkage as long as you have things disassembled
CF Veteran
Joined: May 2011
Posts: 1,458
Likes: 2
From: Glendale,Az
Year: 1990
Model: Cherokee
Engine: 4.0l 6Cyl
Is it just mine or does a lot of early model xjs brakes suck in reverse?
Both my 88 and 90 are horrible in reverse. They literally seem to only use about 25% of pressure to slow down with the pedal fully pressed.
I've adjusted, bled and re bled the brakes multiple times, all new hardware and new master cylinder and they still suck. Going forward they seem to stop fine. They don't lock up but they are much better than going in reverse.
Is there a reason why?
Both my 88 and 90 are horrible in reverse. They literally seem to only use about 25% of pressure to slow down with the pedal fully pressed.
I've adjusted, bled and re bled the brakes multiple times, all new hardware and new master cylinder and they still suck. Going forward they seem to stop fine. They don't lock up but they are much better than going in reverse.
Is there a reason why?
Junior Member
Joined: May 2008
Posts: 15,016
Likes: 11
From: +34° 25' 35.67", -81° 21' 12.04"
Year: 1993
Engine: 4.0
Is it just mine or does a lot of early model xjs brakes suck in reverse?
Both my 88 and 90 are horrible in reverse. They literally seem to only use about 25% of pressure to slow down with the pedal fully pressed.
I've adjusted, bled and re bled the brakes multiple times, all new hardware and new master cylinder and they still suck. Going forward they seem to stop fine. They don't lock up but they are much better than going in reverse.
Is there a reason why?
Both my 88 and 90 are horrible in reverse. They literally seem to only use about 25% of pressure to slow down with the pedal fully pressed.
I've adjusted, bled and re bled the brakes multiple times, all new hardware and new master cylinder and they still suck. Going forward they seem to stop fine. They don't lock up but they are much better than going in reverse.
Is there a reason why?
Newbie
Joined: Aug 2013
Posts: 2
Likes: 0
Model: Cherokee
Chrysler 8.25
It looks like an 8.25. The cover isn't indented. Thanks for the help btw.
Junior Member
Joined: May 2008
Posts: 15,016
Likes: 11
From: +34° 25' 35.67", -81° 21' 12.04"
Year: 1993
Engine: 4.0
CF Veteran
Joined: Oct 2011
Posts: 1,812
Likes: 0
From: South Mills, NC
Year: 1998
Model: Cherokee
Engine: Rebuilt 4.0L I6
Ever cleaned your throttle body and IAC?
Courtesy of TJWalker:
--------------------------------------------------------------------
The Idle Air Control (IAC) is mounted on the back of the throttle body. (front for 87-90) The valve controls the idle speed of the engine by controlling the amount of air flowing through the air control passage. It consists of a stepper motor that moves a pintle shaped plunger in and out of the air control passage. When the valve plunger is moved in, the air control passage flows more air which raises the idle speed. When the valve plunger is moved out, the air control passage flows less air which lowers the idle speed. Over time and miles, the IAC can get carboned up which can have an adverse affect on idle quality. Cleaning the IAC may restore proper function and is an easy procedure to perform and good preventive maintenance so it is never a bad idea.
CLEANING THE JEEP 4.0 IDLE AIR CONTROL
Remove the air filter cover, associated hoses and the rubber boot that goes from the air filter cover to the throttle body. Remove the IAC with a torx driver (2 bolts; one can be kind of hard to get to)
"Gently" wiggle out the IAC from the throttle body. Gasket on the IAC can be re-used if it is not damaged
Clean the IAC with a spray can of throttle body cleaner; inexpensive and available at any place that sells auto parts. Throttle body cleaner is recommended rather than carburetor cleaner as it is less harsh, safe for throttle body coatings and is best for this task. Use cleaner, a rag and a toothbrush and or Q-Tips. Be gentle; don’t twist or pull on the pintle that protrudes from the IAC as it is fragile and you could damage it.
Thoroughly spray clean and flush where the IAC seats in the throttle body with the same spray cleaner
It is also a good idea to clean the entire throttle body itself, the butterfly valve inside of the throttle body and all associated linkage as long as you have things disassembled
Last edited by ccooper1234; Sep 3, 2013 at 02:02 PM.
Junior Member
Joined: May 2013
Posts: 37
Likes: 0
From: Northern Ontario, Canada
Year: 1990
Model: Cherokee
Engine: 4.0 I6
Rear D35 Pinion Seal
I've read some threads saying its just as simple as marking the nut and pinion then taking the nut and old seal out then reverse order. Some say you need to remove tires, axles and have certain tools.
Any clear answer how to do my rear pinion seal? 90 2 DR XJ, D35 Rear.
Thanks!
Any clear answer how to do my rear pinion seal? 90 2 DR XJ, D35 Rear.
Thanks!
CF Veteran
Joined: Apr 2011
Posts: 4,825
Likes: 2
From: Indianapolis
Year: '99 and '91
Model: Cherokee
I think it has to do with the transfer of motion? Lol. That's why they put bigger/better brakes on the front of vehicles. The XJs brakes suck in reverse because they are drum brakes I'm guessing. Braking in reverse would probably be better if you swapped to rear discs.
Moderator of Jeeps
Joined: Jul 2011
Posts: 21,029
Likes: 3
From: Frederick, MD from Cleveland, OH
Year: 1993 YJ Wrangler
Engine: 4.0 I6
That's half. The other half is weight distribution. Passengers are near the front, and the engine sits right above the front brakes, but the rear of the Jeep weighs very little in comparison.
CF Veteran
Joined: May 2011
Posts: 1,458
Likes: 2
From: Glendale,Az
Year: 1990
Model: Cherokee
Engine: 4.0l 6Cyl
I don't see why that effects it. Over all you are still trying to stop an entire vehicle. Do the front brakes just not work when going in reverse? I mean it honestly feels like my rear drums are the only thing attempting to slow the jeep down.
Moderator of Jeeps
Joined: Jul 2011
Posts: 21,029
Likes: 3
From: Frederick, MD from Cleveland, OH
Year: 1993 YJ Wrangler
Engine: 4.0 I6
Shocks help with diving, but you'd have to attach the axles directly to the body and overinflate your tires to completely null the effect.
CF Veteran
Joined: Apr 2011
Posts: 4,825
Likes: 2
From: Indianapolis
Year: '99 and '91
Model: Cherokee
Probable solution, get discs.
CF Veteran
Joined: May 2011
Posts: 1,458
Likes: 2
From: Glendale,Az
Year: 1990
Model: Cherokee
Engine: 4.0l 6Cyl