Wierd Idle Dying Problem
07-20-2017, 08:06 PM
#1
Junior Member
Thread Starter
Wierd Idle Dying Problem - SOLVED
1998 Cherokee 4.0 with Automatic just developed a strange problem. When started it idles fine. But if some gas is given to create a higher idle for a bit, then the gas is let off, the engine dies, or almost dies and if it doesn't die, it idles for a while at like 200 rpm. When restarted it'll idle fine. Unless one gives it some gas. It does this when warmed up. Not sure if it does it when cold.
When driving it does it also but not as bad. When you go to park and take your foot off the gas as you want to shift into reverse, it'll sometimes die or almost die and do the real low idle thing until you give it some gas.
Note that a solid ten years ago the one way valve in the fuel delivery system failed. I'm talking about the valve that is supposed to maintain fuel pressure in the system when the engine is off. If the engine is off for a length of time (maybe 10 minutes or more) when one goes to start it, the engine will crank for several seconds before catching and then run rough for a second or so. I've found the easy solution to this issue is to turn the key to the On position and then wait 2 - 3 seconds for the system to pressurize, and then it'll catch right away and run fine when started. It's basically the same as turning on a cold Diesel and waiting for the Glow Plugs to warm up for a few seconds before cranking the engine - no big deal. But I'm wondering if this is somehow related to the new idle problem (maybe the leak back through the one way valve got worse?). It's probably not but I thought I should mention it.
The other thing to note, is this problem is that this problem first reared its ugly head today after I had to go to my wife's place of work and jump start it. She had left the lights on this morning and completely drained the battery, and when she and a coworker tried to jump start it they were unsuccessful. I'm not going to comment about any of that...
It started right up for me after connecting the jumper cables, but the battery voltage tested at only 7 Volts before I attached the cables, and this was after the lights had been turned off for several hours. So I am sure that when the lights were in the ON position for more than half a day, the battery was drained completely to nothingness. I think this would clear the memory in the ECM and when started it would be reverted back to factory default. I understand that as a car is driven and used, the ECM monitors everything and fine tunes everything as the car ages. Perhaps the factory default settings aren't perfect for an engine with more than 221,000 miles on it. If that's the case and the cause, with a bit of driving the problem should correct itself.
I would welcome any opinions, comments or suggestions.
Best wishes,
John
When driving it does it also but not as bad. When you go to park and take your foot off the gas as you want to shift into reverse, it'll sometimes die or almost die and do the real low idle thing until you give it some gas.
Note that a solid ten years ago the one way valve in the fuel delivery system failed. I'm talking about the valve that is supposed to maintain fuel pressure in the system when the engine is off. If the engine is off for a length of time (maybe 10 minutes or more) when one goes to start it, the engine will crank for several seconds before catching and then run rough for a second or so. I've found the easy solution to this issue is to turn the key to the On position and then wait 2 - 3 seconds for the system to pressurize, and then it'll catch right away and run fine when started. It's basically the same as turning on a cold Diesel and waiting for the Glow Plugs to warm up for a few seconds before cranking the engine - no big deal. But I'm wondering if this is somehow related to the new idle problem (maybe the leak back through the one way valve got worse?). It's probably not but I thought I should mention it.
The other thing to note, is this problem is that this problem first reared its ugly head today after I had to go to my wife's place of work and jump start it. She had left the lights on this morning and completely drained the battery, and when she and a coworker tried to jump start it they were unsuccessful. I'm not going to comment about any of that...
It started right up for me after connecting the jumper cables, but the battery voltage tested at only 7 Volts before I attached the cables, and this was after the lights had been turned off for several hours. So I am sure that when the lights were in the ON position for more than half a day, the battery was drained completely to nothingness. I think this would clear the memory in the ECM and when started it would be reverted back to factory default. I understand that as a car is driven and used, the ECM monitors everything and fine tunes everything as the car ages. Perhaps the factory default settings aren't perfect for an engine with more than 221,000 miles on it. If that's the case and the cause, with a bit of driving the problem should correct itself.
I would welcome any opinions, comments or suggestions.
Best wishes,
John
Last edited by mdtobe; 07-21-2017 at 03:26 PM. Reason: I think the problem is now solved.
07-20-2017, 09:48 PM
#2
I have been burned by a drained battery on my '99 twice. I was able to jump it, but it just wouldn't idle. I put it on a battery tender for a day to charge it and it still wouldn't idle. Started replacing things and then finally gave in and got a new battery. That solved it. Happened again a while alter. After some research, it seems like the XJs just do not like to start and definitely do not like to idle with a weak battery. I have been able to jump/charge batteries on many other cars with no ill affects. But on my XJ, it just doesn't work once a battery is marginal.
07-20-2017, 11:47 PM
#3
Junior Member
Thread Starter
I have been burned by a drained battery on my '99 twice. I was able to jump it, but it just wouldn't idle. I put it on a battery tender for a day to charge it and it still wouldn't idle. Started replacing things and then finally gave in and got a new battery. That solved it. Happened again a while alter. After some research, it seems like the XJs just do not like to start and definitely do not like to idle with a weak battery. I have been able to jump/charge batteries on many other cars with no ill affects. But on my XJ, it just doesn't work once a battery is marginal.
07-21-2017, 06:35 AM
#4
CF Veteran
I was told by a friend who is a service manager at at Chrysler dealership and is a jeep guy, that the IAC needs to relearn its parameters. That being the reason jeeps won't idle right away once the battery has been drained.
From experience they are usually fine once the jeep is ran for a while. Sometimes it takes longer than others. Possibly depending on how far drained the battery was and what condition the battery is actually in.
From experience they are usually fine once the jeep is ran for a while. Sometimes it takes longer than others. Possibly depending on how far drained the battery was and what condition the battery is actually in.
07-21-2017, 03:30 PM
#5
Junior Member
Thread Starter
Wierd Idle Dying Problem - SOLVED
Hi everybody,
I think we can consider this one to be solved. As I suspected and several people suggested, the total drainage of the battery caused by the lights being left on all day erased the computer's memory of its fine tuning of the idle parameters. It started up and ran perfectly today for my wife as she drove around town food shopping at various stores. It seems to have relearned its settings in the drive home from her workplace last night (about 22 miles mixed expressway and city traffic).
Thanks for the input!
Cheers,
John
I think we can consider this one to be solved. As I suspected and several people suggested, the total drainage of the battery caused by the lights being left on all day erased the computer's memory of its fine tuning of the idle parameters. It started up and ran perfectly today for my wife as she drove around town food shopping at various stores. It seems to have relearned its settings in the drive home from her workplace last night (about 22 miles mixed expressway and city traffic).
Thanks for the input!
Cheers,
John