Topic: Idle issues

[bammerman]

I found this thread but there was no response

http://4bangerjp.com/forums/index.php?topic=4440.0

When I am sitting at a dead stop is it up to 2000 to 2500 RPM's and when I shift it goes back down to 1-1.5k

This doesn't seem right...

[TrailsLessTaken]

You check your vacum hoses on the intake to see if one came loose?

[chardrc]

so this is a tbi 2.5l? if it is take a look at this http://jeepgarage.free.fr/OWN/fuel%20injection%20system%20tbi.pdf. isa motor sets the idle speed (from what the computer tells it). can you describe your situation a little more and what you have (whats happened in the last 2 years)... whats supposed to happen is when you shut off the jeep the asi motor fully extends (pushed throttle open a bit) to help with starting. then when you start up the jeep it lowers the idle to a regularly idle speed 900rpm-ish (which obviously isn't happening in your case) but since the idel rpm do change since you said it goes down to 1.5k when shifting... like previously said check the vacuum lines make sure you didn't miss any. there are some that are easy to miss (i did at least). there is one that connects under the line for the brake booster on the manifold side that is easy to miss. and they 2 from the hvac system coming out of the firewall like to fall off on my jeep. also make sure all wired connections are in good condition. hope this helps and we can be more helpful than in 2008

timing is controlled by the computer. only change you can do is move the cps a bit.

[bammerman]

You check your vacum hoses on the intake to see if one came loose?

I am not very savy, where would this be located?

[TrailsLessTaken]

They will be on the intake near the throttle body, I think there are 3 or 4 of them I cant remember off the top of my head.  What year jeep do you have?

[bammerman]

1990 YJ, I checked on the TB but nothing seemed unplugged.  It just started happening recently, maybe within last month.  Only thing I have done is add some KC lights, a new clutch and new oil pan and valve cover gaskets.

[chardrc]

they are the 2 that are more of a hard plastic, one comes from the firewall on the passenger side of the motor and connects into a check valve by the charcoal canister, and the other comes out of the firewall on the drivers side and also connects into a check valve and connects into the metal vacuum harness thing somewhere but i don't remember right now where exactly.. problem ive had with them is the hard plastic to rubber transition gets looser with time and if you have an oily engine bay like mine they get slippery and like to fall off when you hit rough terrain unless you secure them better (i used zip ties) im guessing that that isn't your issue though (or at least not all of it) since with those off mine still manages to idle down to 1.2kish it just takes a bit longer to idle down and runs rougher..

[TrailsLessTaken]

I'm not sure on yours, I havent worked on one of the throttle body injection ones yet

[bammerman]

it is odd, sometimes I sit at 2k but then others it goes up to 2.5k and stays steady.  I checked the lines and nothing is d/c'ed.  Not sure if this matters but oil, and radiator fluid good.  Not sure where to go next.

[sharpxmen]

it is odd, sometimes I sit at 2k but then others it goes up to 2.5k and stays steady.  I checked the lines and nothing is d/c'ed.  Not sure if this matters but oil, and radiator fluid good.  Not sure where to go next.

i have no experience with the tbi setup and the guys before me covered most of the issues specific to that - so just going on a guess here and since it has not been mentioned: have you checked the throttle and try to move it back by hand? i'm just thinking that the return spring might be the issue, the accelerator cable has some problem and not letting the throttle return to minimum position or maybe the butterfly shaft/assembly get's stuck somehow - see if that brings the idle back down (try to also maybe unhook the cable). Check if the position of the butterfly lever is at the minimum where it should be for idle and like chadrc suggested also check and see if the idle control motor is keeping the throttle open.

[chardrc]

have you checked the throttle and try to move it back by hand? i'm just thinking that the return spring might be the issue, the accelerator cable has some problem and not letting the throttle return to minimum position or maybe the butterfly shaft/assembly get's stuck somehow - see if that brings the idle back down (try to also maybe unhook the cable). Check if the position of the butterfly lever is at the minimum where it should be for idle and like chardrc suggested also check and see if the idle control motor is keeping the throttle open.

x2 on that with the tbi there is a built in return spring in the tb (like the mpi guys have kinda)and an additional spring that looks like th one in the picture (not exactly the same as the stock one broke before i got it and this is some random one the po put on, which is why i am x2 what sharpaxmen said because the spring actually broke on mine and could possibly cause the problem in conjunction with a obstruction to the cable somewhere)



this is actually a pretty good picture of the asi motor for those wondering what it looks like.

[sharpxmen]

this is actually a pretty good picture of the asi motor for those wondering what it looks like.

he could also unbolt that ias motor once the engine is warm to see if it makes a difference (if all the other things check out ok).

[bammerman]

This is what I came up with... Is there a way to clean it?  or is it the spring like you all said it could be?  I tried adjusting the screw and nothing, but I push on that bar toward the thing with spring and it idels down to 1.0

[chardrc]

ok your return spring is in the stock setup(mine is wrong but works) so that should be good. when you push the throttle closed are you forcing the isa (what i was talking about before but i misspelled it) motor to retract or are you just pushing in the end cap of it (the end part should push in a little which is the closed throttle switch which tells the computer to take over idle control). if you are just pushing in the little end cap (closed throttle switch) then i would suspect binding in the linkage or a weak return spring.if you are having to physically force the isa motor plunger in then i would try adjusting it according to the top of page 6 in the link  (don't know if you meant you fallowed that or you where just randomly trying to adjust the screw). other than that i don't know of any special way to clean it.. good luck

http://jeepgarage.free.fr/OWN/fuel%20injection%20system%20tbi.pdf

[sharpxmen]

ok your return spring is in the stock setup(mine is wrong but works) so that should be good. when you push the throttle closed are you forcing the isa (what i was talking about before but i misspelled it) motor to retract or are you just pushing in the end cap of it (the end part should push in a little which is the closed throttle switch which tells the computer to take over idle control). if you are just pushing in the little end cap (closed throttle switch) then i would suspect binding in the linkage or a weak return spring.if you are having to physically force the isa motor plunger in then i would try adjusting it according to the top of page 6 in the link  (don't know if you meant you fallowed that or you where just randomly trying to adjust the screw). other than that i don't know of any special way to clean it.. good luck

http://jeepgarage.free.fr/OWN/fuel%20injection%20system%20tbi.pdf

is it possible that the throttle position switch is in the wrong position? so the control is sent to PCM before his throttle is all the way back? i have no idea how the tbi is setup but just going on some guess work here based on what you 2 are saying.

i still think would be a good test to unbolt the isa motor and see if the idle goes down (to rule out the binding or cable problems) and he should maybe also check when that microswitch is closing (i assume if it's hit before the idle position that the isa would take over and hold the idle high, but again this is guessing so maybe you can clarify how it works)