Topic: Idle issue (any thoughts?)

[jfrabat]

Hey, guys, I have been going over my idle issue (in my head, anyway, because I am currently in Tokyo and the Jeep is still in Miami!) and I was asking myself (note that my Haynes and Chilton manuals are in Miami with the Jeep!) if the '94 YJ 4 popper had any air temperature, because when the weater gets cooler, the idle drops a bit...

As far as I remember, there are no Air Temperature sensors, but is this right?  If there are no sensors, could it be maybe the MAP sensor acting up?

I still have to check for vacuum leaks (was going to do that last weekend, but the Jeep Fest kind of got in the way!  ) but I am trying to figure out other possibilities in my head so I check everything when I get back...

For those that did not read my prior posts, the issue I have is that the idle in my Jeep is about 900 RPM's (regardles if I use the 2.5L or the bored out 4.0L TB).  Also, I AM using the 2.5 IAS (housing and motor), so that is not the issue.  With the 4.0L TB on, after I cruise on the Highway for some time, as I get off the ramp, the idle sets at 1,500 RPM's more or less, and then slowly drops back to 900 RPMs (every few seconds it drops about 100 RMPs untils it settles back down).

In the case of the 4.0L TB, there is a VERY SLIGHT gap on the sides of the plate, but I think the IAS should be able to handle and compensate for that (besides, this is not seen in the 2.5L TB, and the idle is still at around 900 RPM with that TB on).

The main reason I am trying to bring the idle back down to normal is to improve mpg, obviously, because to be honest, the rig is running great (except for this, and the brake booster which will need to be replaced before witching to 33s).

Any ideas?

Felipe

[jcoleman]

wanna start an idle issue club? we can have semi annual meetings/ competitions to see whose rig idles worse without stalling out.  I bet i win.

My jeep idles fine at a dead stop or when warming up.  Other wise i have to keep it in gear while slowing down until the rpms reach somewhere in the 800 to 1000 range, then i slowly push the clutch in, and it sometimes stays there.  But not always, most times it drops down to about 200 sometimes less and fluctuates between there and 400.  it also does this if I just push the clutch in when slowing down whenever the rpms are above 1000.

so pretty much we are like opposites. me low you high.

[jfrabat]

wanna start an idle issue club? we can have semi annual meetings/ competitions to see whose rig idles worse without stalling out.  I bet i win.

My jeep idles fine at a dead stop or when warming up.  Other wise i have to keep it in gear while slowing down until the rpms reach somewhere in the 800 to 1000 range, then i slowly push the clutch in, and it sometimes stays there.  But not always, most times it drops down to about 200 sometimes less and fluctuates between there and 400.  it also does this if I just push the clutch in when slowing down whenever the rpms are above 1000.

so pretty much we are like opposites. me low you high.

Tell you what; I'll give you a couple of Idle RPM's (you just pay for shipping!)...    

In my case, I can tell you  it is not the MAP sensor or the vacuum lines, because I replaced those and I still have the issue.  I actually thought it was a vacuum fitting that was a little loose on the line, but I replaced it and it made no difference.

Felipe

[TN00TJ]

"My jeep idles fine at a dead stop or when warming up.  Other wise i have to keep it in gear while slowing down until the rpms reach somewhere in the 800 to 1000 range, then i slowly push the clutch in, and it sometimes stays there.  But not always, most times it drops down to about 200 sometimes less and fluctuates between there and 400."

This is what mine just started doing on Monday. I've only started searching "low idle" posts but if someone wants to jump in with a fresh thought, it would be most welcome.

Thanks,

Bruce

[sharpxmen]

"My jeep idles fine at a dead stop or when warming up.  Other wise i have to keep it in gear while slowing down until the rpms reach somewhere in the 800 to 1000 range, then i slowly push the clutch in, and it sometimes stays there.  But not always, most times it drops down to about 200 sometimes less and fluctuates between there and 400."

This is what mine just started doing on Monday. I've only started searching "low idle" posts but if someone wants to jump in with a fresh thought, it would be most welcome.

Thanks,

Bruce

i would think in this order
TPS
IAC
injectors

any codes?

[jfrabat]

Holy old thread, batman!  My issues have always been with HIGH RPM's not low, so you got me with this one...

I would normally think of the cat as well, but that would be more of an issue when accelarating than when decelarating...  Start with what Sharp mentioned, and let us know how it turns out.