XJ won't idle/has trouble starting... i'm out of ideas.

[Crossett]

I went to start the XJ one day and the starter just clicked. Jumped it off another vehicle and it started fine, but wouldn't hold an idle, I had to keep the throttle open or it would just die. It had seen a little mud the week prior to this, so I figured that that alternator was toast. Replaced it, same thing. At this point I was still thinking that mud had killed the alternator and that I drove around for a while just running on the red top which had eventually given up. Took the battery out and had it warranteed. Put the new battery in and it's doing the same thing. It was a little hesitant to start and when it did it wouldn't stay running without me holding the throttle open.

Other than replace what I already have i'm not sure what else could be wrong. Do you guys have any ideas?

 

[scoobyxj]

Starter still clicking, or just doesn't want to idle?

 

[Crossett]

Starter still clicking, or just doesn't want to idle?

Just doesn't want to idle.

 

[Jeepsloth]

what year is it?

 

[cygnus58]

My '88 wouldn't idle unless i flailed on the throttle. Even then, pops and stalls.And not enough power to pull out of the driveway, literally.
My CPS went bad all of a sudden.

 

[Crossett]

what year is it?

99 4.0

 

[scoobyxj]

Take it for a drive. Don't romp on it just a normal spin around the block, or up the road, and back. Be prepared for it to want to stall the first couple times you come to a stop. Left foot break so you can keep it running. It should relearn the idle in a couple hundred feet. Though it still might act a bit funny for a little while till everything is relearned.

 

[Crossett]

Take it for a drive. Don't romp on it just a normal spin around the block, or up the road, and back. Be prepared for it to want to stall the first couple times you come to a stop. Left foot break so you can keep it running. It should relearn the idle in a couple hundred feet. Though it still might act a bit funny for a little while till everything is relearned.

After I replaced the alternator, but not the battery and jump started it it didnt want to idle either. I left it connected to the vehicle I jumped it with and left that vehicle running for ~20 minutes. When I went back to it it started and idled. I drove it around for a while to charge the battery. When I shut it off it didnt want to start again. I assumed that I had run the battery all the way down and killed it.

This makes sense, i'll go put some miles on it and see if it "learns" what it needs to again.

 

[90Blue_XJ]

Take it for a drive. Don't romp on it just a normal spin around the block, or up the road, and back. Be prepared for it to want to stall the first couple times you come to a stop. Left foot break so you can keep it running. It should relearn the idle in a couple hundred feet. Though it still might act a bit funny for a little while till everything is relearned.

Yeah when the battery is disconnected you rob the ECM of its memory so it needs to start over again. It may take up to 40 re-starts until it has sufficent memory to idle like it did before. So don't be in a hurry for it to relearn. Have patience with it.

 

[Craig96_XJ]

this happened to me a few months after i replaced the alt. and i found out that my battery terminals were corroded to shit. got them replaced and charged the battery and everything has run fine since then

*pooʍ uo ʞɔouʞ*

 

[Crossett]

I just put about 25 miles on it. It didn't really want to idle for the first half or so, but seems to be ok now.

 

[UNCC_99XJ]

Take it for a drive. Don't romp on it just a normal spin around the block, or up the road, and back. Be prepared for it to want to stall the first couple times you come to a stop. Left foot break so you can keep it running. It should relearn the idle in a couple hundred feet. Though it still might act a bit funny for a little while till everything is relearned.

X2. Last time my XJ sat for a week, stupid me left my radar detector plugged in and it killed the battery. Computer lost its memory, and it ran like absolute crap. Charged the batter back up and it would just sit there and crank, but not fire without me assisting it.

It seemed to get an idle back when it got up to temp, but the first couple of stops I made while driving it around the block and it tried to stall out again. Gave it a few miles, and a couple of restarts and all was well.

Sounds like you've fixed your problem And like Scooby said, it might bounce around on the idle for a little while longer, but it shouldn't be anything too horrible....just enough that you'd notice it.

edit: If it keeps doing this (no start unless throttle is applied) long after the computer has relearned everything, I would begin to look into a new TPS. I also had this problem long after the battery incident, and it would randomly not fire....just sit there and crank all day. It would also slip out of OD/4th while crusing on occasion. Finally got around to hooking a scanner up to it to monitor the TPS reading while I was driving, and the minute it started to slip b/w 3rd and 4th/OD, I looked at the scanner and sure enough, the TPS readings were changing, eventhough I wasn't changing the throttle. Just something to keep in the back of your head.