cheap IAC fix

okay sometimes my 4.0 will rev to about 3000 when u start it and not come down. so today i think i fixed it with some hillbilly engineering. i took a thin peice of stainless steel, and drilled a hole in one end, its a rectagnle about 3 by 1 inches, with the hole on one end, i took the intake tube off and ran one of the bolts thru the hole in the stainless steel where it was lined up and covering the hole that leads to the IAC, then tightend it all down. so now it doesnt rev to 2k when i start it and slowly come back down, and it cant rev to the moon idle. i left the IAC in and pluged in still, it runs fine, cant tell i diff exept idles lower now, so basicaly i blocked of the hole to the iac with a peice of stainless between the TB and air intake. so what does everyone think of this fix? should it be okay?

kolby

lankchevy said:

hillbilly engineering

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you said it all right there ^^^

you are fixing a symptom. not the problem.

what year xj?

its an 88 with renix, ive changed the iac, and cleaned the C101 conector, i realy dont know what else to do about it,i just know its realy anoyying when u get in ur jeep and need to go somewhere and u cant cause it wants to idle at 3000 rpm, and its kinda embarassing when u have to start and turn it off 7 or 8 times trying to get it to idle right, sometimes it will be normal after the 3 or 4, and sometimes it doesnt matter how many times u turn it off and start it again.

kolby

cleaned the C101 conector

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did you pull off the outside dust covers and clean the backside of the terminals?

thats where mine was making inapropriate contact, esp. when it got wet.
dirt had filled in the terminal ports, cleaned them out thouroghly and fixed the same problem.

Could also be the tps.

High Idle on Renix XJs

On my 1990 with the 4.0l engine, high idle always resulted from a dying TPS. Its on its third one now. (Could also be idle leak, but that would not likely be erratic/intermittent. Your symptoms sound like a sensor issue.) Have you checked the TPS for signal values?

Re: High Idle on Renix XJs

havent checked the tps signal values, i checked and cleaned the plug at the IAC, yes i took the c101 apart, thourghly cleaned it, then put new dialectric grease in it, and it did basicly nothing. ill search for the writeup on checking the tps.

kolby

lankchevy, I am in the same boat as you. No hillbilly engeneering here though. Did all of the same things. I have even replaced the IAC, TPS, and cleaned the C101. I'm at a loss too. :dunno:

hmm well might want to try what i did then, cause so far its still working just fine. and its nice not having it rev up to 2k EVERY time u start it then slowly go back down.

kolby

Mine is just a little different. Mine will start and idle just fine, when I step on the accelerator hard is when it sticks at about 2500 rpm's. And no the throttle plate is not sticking. Everything has been cleaned, checked and rechecked.

mine did that too sometimes, it would start fine, then id put it in gear, drive to whereever, then when i put it in park would go to 2500. when it did that if u shut it off then back on it was okay again.

kolby