wierd issue....

ok i am searching..for my issue, so bear with me please.....

i originally thought this issue was just a weird bug in my xj(see sig), however the other day my girlfriends new(for her) 97 zj (V8 quadradrive,170,000)did it to..much to my surprise....

the problem....
every so often(twice now in hers and for about the last three months in mine.)...occasionally, when we go to fire up our jeeps, we get them to fire but when we take our foot off the gas to apply the brake to shift from P to D. they just idle right on down and cut out real quick like....so i have learned, that when this happens i need to refire it and keep my foot on the gas, apply the brake with my other foot and keep it going for a minute...let it run then kill it and refire................usually when we refire everything seems to run right again....

very weird and it has me puzzled considering the different model jeeps with the same prob....

appreciatte any info you all have that might point me in the right direction....

i am searching under for stall and motor cut out any other ideas....


edit: figure this might be needed....my xj is usually cold(start) when this happens...the first time the zj did it it was a cold start the last time while i was driving it we had just finished a two day hike fired it up drove 10 min to the local gas station and when i went to fire it back up no dice...odd?

Just some thoughts, during the startup the computer does not control the fuel pump until after it is running, at least as I understand it. At that point the computer/ecu takes over using input from the CPS. Before I would replace the CPS I would, 1- clean the throttle body and the sensors in it. Unplug and clean the CPS connector using dielectric grease when I plugged it back together, I don't know where it is on the V8 but it should be easy enough to trace from the bell housing unless it uses one in the front, again not familiar with the V8's. It could be something in the tranny or TCU but again I don't know much about automatics and how they interact. Will it just keep idling if you just start it and let it run ? What happens if you leave it in park and jiggle the gas pedal ?
What happens if you let it run for say 5 min when cold and then try to go ?

Rich: response to your questions..

"Will it just keep idling if you just start it and let it run?"----no it usually cuts out before you can get it out of park.

"What happens if you leave it in park and jiggle the gas pedal"---i have to feather the pedal just to keep it going..if i dont feather the gas in P, she dies...

"What happens if you let it run for say 5 min when cold and then try to go ?"
we never really get that far, if i dont keep the gas on it they just die...real weird...we end up shutting it down and then retrying a couple times to where it eventually starts up like nothing was wrong...although my girl says the first time it happened to her it took twenty minutes to start properly....

I'd start with a couple of things, first would be to check the throttle position sensor with a meter, it's on the throttle body and and sends a signal to the ECU as to how far the throttle is open. I'd also look for a vacum leak, maybe. With the age of the vehicles connector corrosion might be starting to become an issue so pulling connections apart and cleaning them then applying some dielectric grease might not be a bad idea.

Load Test The Battery

jeepurnaz said:

Load Test The Battery

Click to expand...

Yea, that can do some weird stuff too.

Grifter144 said:

the problem....
every so often(twice now in hers and for about the last three months in mine.)...occasionally, when we go to fire up our jeeps, we get them to fire but when we take our foot off the gas to apply the brake to shift from P to D. they just idle right on down and cut out real quick

Click to expand...

So if I understood that properly, you have your foot on the gas while cranking it? Why do you do that? Is it possible you are flooding the engine out during start up?

Grifter144 said:

Rich: response to your questions..

"Will it just keep idling if you just start it and let it run?"----no it usually cuts out before you can get it out of park.

"What happens if you leave it in park and jiggle the gas pedal"---i have to feather the pedal just to keep it going..if i dont feather the gas in P, she dies...

"What happens if you let it run for say 5 min when cold and then try to go ?"
we never really get that far, if i dont keep the gas on it they just die...real weird...we end up shutting it down and then retrying a couple times to where it eventually starts up like nothing was wrong...although my girl says the first time it happened to her it took twenty minutes to start properly....

Click to expand...

Do you and your GF buy gas at the same station?

Are you seeing this on cold starts, or when the engine is already warm/hot? You might want to check out this thread: http://www.naxja.org/forum/showthread.php?t=62409

I've been starting to see this regularly in my '01 Sport, significantly more with midwest/Ohio gasoline. I think I'll give the suggested fix a try.

Also, definitely do check your battery. If mine is dead (jump start) or low (barely manage to start), the Jeep won't idle at all until it's built up some charge. I have to drive around or keep the gas pedal down for at least a couple of minutes before it'll hold an idle, more if the battery was really drained.

Either way, the "kill and refire" thing you mention kinda baffles me...are you sure that's something you *have* to do in order to get it to run?

As far as flooding the engine, IIUC that should no longer be an issue with EFI, though I could be mistaken.

99XJSPORT06 said:

So if I understood that properly, you have your foot on the gas while cranking it? Why do you do that? Is it possible you are flooding the engine out during start up?

Click to expand...

i'm sorry i miss worded that.....when I turn the key to start it up, the starter kicks in and she turns over for a moment so that i think she is good to go..seems that the rpm goes up to like say 2500 and then settles back on down to like 800 where it would normally idle right...occasionally this issue happens and instead of idling at 800 or so (whatever idle nromally is) it just winds on down to nothing and dies...unless i apply my heavy righty to the peddle and keep the rpm up with the peddle.....is this making any sense...it baffles me that this problem is happening to two different vehicles with different motors....

thanx for the input guys.....

my old man suggested cleaning off the battery as apprently dirty batterys lead to creeping electricity which would cause a battery to slowly short itself out....so we'll see....i also figured out today that i have a short in the door speaker wire as the radio will cut out if the door is opened while the jeep is running...very weird....time to fish some wires......

Maier

pyrotech said:

Are you seeing this on cold starts, or when the engine is already warm/hot? You might want to check out this thread: http://www.naxja.org/forum/showthread.php?t=62409

I've been starting to see this regularly in my '01 Sport, significantly more with midwest/Ohio gasoline. I think I'll give the suggested fix a try.

Also, definitely do check your battery. If mine is dead (jump start) or low (barely manage to start), the Jeep won't idle at all until it's built up some charge. I have to drive around or keep the gas pedal down for at least a couple of minutes before it'll hold an idle, more if the battery was really drained.

Either way, the "kill and refire" thing you mention kinda baffles me...are you sure that's something you *have* to do in order to get it to run?

As far as flooding the engine, IIUC that should no longer be an issue with EFI, though I could be mistaken.

Click to expand...

i see it on my 2k xj on cold starts.....my girls 97 zj though did it the other day after i had driven it for like twenty minutes up north on a cool day out in the country side.....very weird.....as for the kill and refire thing.....it dies(as in kill and then inorder of natural progression i have to refire it to attempt to get where i need to go....
Maier

Grifter144 said:

i see it on my 2k xj on cold starts.....my girls 97 zj though did it the other day after i had driven it for like twenty minutes up north on a cool day out in the country side.....very weird.....as for the kill and refire thing.....it dies(as in kill and then inorder of natural progression i have to refire it to attempt to get where i need to go....
Maier

Click to expand...

Again lot and lots of bad gas out there, do you and your GF buy your gas at the same place?

Clean your throttle body. Sounds like your idle air valve is not opening. But it could be all of the above too. Happy hunting.

The speaker short most likely will be the green with red stripe in the rubber boot to the drivers door has broken.