I've been searching through threads for my problem but can't find one, although I'm sure I'm not the first. The problem: when I start my jeep cold everything seems to work fine, after driving awhile and warming up the idle becomes rough. Sometimes at complete stops it will die. The other day it died, I restarted it, the idle went up past normal and immediately died, repeated that step 4 or 5 times. I've heard maybe the CPS sensor, but I have no clue. Tried injector cleaner, no help. Also it is VERY slow on acceleration, it will sputter some, not responsive at all. Any help??
-
Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.
PITA idle problems!
- Thread starter xj-sparky
- Start date
89xj4.0
NAXJA Forum User
- Location
- Des Moines, Iowa
what year and model? with what motor?
89xj4.0
NAXJA Forum User
- Location
- Des Moines, Iowa
im guessing you have an xj with a 4.0, if so look on the driver side fender up by the airbox. there should be a fuel pump resistor that has two wires going to it. it is probably made out of plastic or ceramic. make sure both wires are in their correct places. if this does not fix the problem i would suggest the EGR valve be replaced
Muad'Dib
NAXJA Forum User
- Location
- Bend, Oregon
If its a pre 91 (87-90) then it has an EGR valve. Since you have a 94, you dont have one. Have you checked all the vacuum lines? Adjusted your TPS? Cleaned your throttle body and IAC? I would try these things.
Last edited:
89CherokeePioneer
NAXJA Forum User
- Location
- Massachusetts
I would go to your local autozone and pick up a Haynes. Or chiltons. Ideally a Factory service manual, but for now Haynes is better than nothing.
Hate to be a prick, but the items he suggested are pretty standard. If you've worked on any FI car for driveability issues, these are typically looked at first.
The vacuum lines are thin rubber hoses (some near firewall are colored, others are plain black) With the engine running (mind the fan!) listen to each for a leak, and cracks etc. If your vents and whatnot work without issues, this probably isn't the case. I doubt its a vacuum issue anyway, since when its cold thats when it needs the fuel most. It can run a little leaner than normal when its hot.
I'll find a guide or something around for TPS adjustment and Throttle body cleaning. The TPS incase you dont know, tells the engine how much throttle your giving it, and it adjusts fuel mixture among other things accordingly.
Hate to be a prick, but the items he suggested are pretty standard. If you've worked on any FI car for driveability issues, these are typically looked at first.
The vacuum lines are thin rubber hoses (some near firewall are colored, others are plain black) With the engine running (mind the fan!) listen to each for a leak, and cracks etc. If your vents and whatnot work without issues, this probably isn't the case. I doubt its a vacuum issue anyway, since when its cold thats when it needs the fuel most. It can run a little leaner than normal when its hot.
I'll find a guide or something around for TPS adjustment and Throttle body cleaning. The TPS incase you dont know, tells the engine how much throttle your giving it, and it adjusts fuel mixture among other things accordingly.
Muad'Dib
NAXJA Forum User
- Location
- Bend, Oregon
Definetly pick up a book, it will help you alot. I havent looked at a chiltons for a Jeep, i have a Haynes. It seems to be taylored more towards the RENIX era Jeeps (87-90). I dont know if the Chilton is that way or not maybe someone else can tell us. If it isnt then since you have a 94 pick up the chilton. I know my haynes has been a blessing for my 90, but if i had a 91+ some things may get confusing. Everyone keeps talking about an FSM (Factory Service Manual). I should get one, but with all the info, and helping hands on this site..its like you do have an FSM.
Do as 89 said with the vacuum lines. Listen carfully for a hiss. If you find one, its abvious that you have a vacuum leak. Find where the hiss is coming from, and replace the plastic or rubber vacuum line thats causing it.
Cleaning the IAC is pretty straight foward. Remove it from the throttle body, and spray it with carburator cleaner. Make sure the tip of it (aka pintle) has no grooves in it, it could be getting stuck. The spot where it goes into the TB also needs to be inspected. Clean it up really good with the carb cleaner as well.
Cleaning the TB is the same process. Leave the engine running and spray the CC across the throttle plate while slightly moving the throttle lever to prevent the engine from stalling out. This will not only clean your TB, but it will slightly clean up your intake manifold and the top of your engine. If you wish to clean the top of the engine to the best of your ability, do a search for seafoam.
As far as adjusting your TPS, thats probably the most complicated to do. Do a search here to get the instructions on how to do it. You will need a multimeter.
Hope that helps.
Do as 89 said with the vacuum lines. Listen carfully for a hiss. If you find one, its abvious that you have a vacuum leak. Find where the hiss is coming from, and replace the plastic or rubber vacuum line thats causing it.
Cleaning the IAC is pretty straight foward. Remove it from the throttle body, and spray it with carburator cleaner. Make sure the tip of it (aka pintle) has no grooves in it, it could be getting stuck. The spot where it goes into the TB also needs to be inspected. Clean it up really good with the carb cleaner as well.
Cleaning the TB is the same process. Leave the engine running and spray the CC across the throttle plate while slightly moving the throttle lever to prevent the engine from stalling out. This will not only clean your TB, but it will slightly clean up your intake manifold and the top of your engine. If you wish to clean the top of the engine to the best of your ability, do a search for seafoam.
As far as adjusting your TPS, thats probably the most complicated to do. Do a search here to get the instructions on how to do it. You will need a multimeter.
Hope that helps.
88xjlover
NAXJA Forum User
- Location
- Marysville, WA
From what I've read there is no adjustment for TPS after 1990 model xj's. 4.0 HO I'm assuming.
It may still be the problem and a good book will tell you how to test it. Try searching for idle problems there is a lot of info and instructions here.
Good luck!:wave1:
It may still be the problem and a good book will tell you how to test it. Try searching for idle problems there is a lot of info and instructions here.
Good luck!:wave1:
ParadiseXJ
NAXJA Forum User
- Location
- Paradise, CA 95969
jdtido37
NAXJA Forum User
- Location
- Cross Lanes, West Virginia
I had the same problem with my 96 4.0 XJ. I replaced my o2 sensors and surely enough that did the trick. Check engine light on?
