if i unplug the IAC & nothing happens does that mean the IAC is bad?

team510 · Apr 18, 2007

My idle has been rough and slightly high since i bought my jeep (88 XJ 4.0). its got a new TPS and Im pretty sure my vacuum is good. One time i took off the IAC and it was all gunked up and i cleaned it really good and my idle was like perfect after that....for that night. next day it was back up again. in park around 1000-1100 when cold and slightly higher when warm, and it barely drops in gear. prob around 900 rpm or so and eventually when warm is right up at 1000-1100.

so i checked the IAC yesterday by disconnecting it while the motor was running and nothing happened. does that mean its not working to begin with if nothing changed when i unplugged it? would that cause my high idle and kind of rough fluxuations in my idle? (it kinda bounces up and down by 100 rpms or so while idleing)

help! it drives me nuts. my friends idles perfect at like 500rpm and is totally snooth. ive been searching all over this board and have tried almost everything. ran seafoam through the brake booster vacuum line yesterday too and nothing changed.

8Mud · Apr 19, 2007

When you unplugged it, it stayed right where it was at. The IAC is basically a rod with a stopper at the end, the rod is notched and there is a motor inside the IAC that moves the rod in and out.
The lubrication on the rod is a grease (at least on the IAC's I've looked at behind the piston). The grease collects pretty much the same gunk you cleaned off of the piston. Spraying a solvent behind the piston (stopper) may cause grief. I occasionally squirt a little penetrating oil behind the piston and let a drop or two of synthetic oil flow behind the piston, then repeat a few days later. I usually have good function for months or sometimes a year, then repeat the process.
Messing with the piston can strip the motor gears or the notches on the rod. It can also launch the rod and stopper across the garage. Don't ask, you know the answer, duh! I did that..

Ecomike · Apr 22, 2007

team510 said:
My idle has been rough and slightly high since i bought my jeep (88 XJ 4.0). its got a new TPS and Im pretty sure my vacuum is good. One time i took off the IAC and it was all gunked up and i cleaned it really good and my idle was like perfect after that....for that night. next day it was back up again. in park around 1000-1100 when cold and slightly higher when warm, and it barely drops in gear. prob around 900 rpm or so and eventually when warm is right up at 1000-1100.

so i checked the IAC yesterday by disconnecting it while the motor was running and nothing happened. does that mean its not working to begin with if nothing changed when i unplugged it? would that cause my high idle and kind of rough fluxuations in my idle? (it kinda bounces up and down by 100 rpms or so while idleing)

help! it drives me nuts. my friends idles perfect at like 500rpm and is totally snooth. ive been searching all over this board and have tried almost everything. ran seafoam through the brake booster vacuum line yesterday too and nothing changed.

Remove and clean all the ground wires connected to the engine block, one is on the passanger side next to the oil dip stick then the drivers side on the valve body of the engine, then the two on the firewall and then the battery ground post. Then you need to adjust the TPS position sensor at idle, so that it reads 0.82 to 0.83 volts at idle across the B and C connectors of the three wire connector on the TPS with the connector attached! Do the adjustment with the engine off but the power on (Just don't start it). That should solve your problem! It solved mine after 2 years and a dozen other parts and fixes failed too!

if i unplug the IAC & nothing happens does that mean the IAC is bad?

team510

NAXJA Forum User

8Mud

NAXJA Forum User

Ecomike

NAXJA# 2091

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