Bad IAC?

djk8705 · May 9, 2004

I took everyone's advice and took off my t/b and IAC to clean with come carb cleaner and man was the IAC dirty and same with the t/b but when i put it back on now my car idles very weird. It will idle at 1200-1300 rpms and when i get off the gas while driving and go to neutrual it stays at like 2300rpms till i totally stop.. then it come back to 1300rpms or so. Also When I am shifting, in between shifts when i push the clutch in, the rpms go up a little as if i am giving it some gas or somthin. Did i mess up the IAC? I tried resetting the TPS but i coulnt fix the idle at all, then lowest i could get it was the 1200rpms or so.... Any help? any thoughtS? replase tps? replace IAC? thanks

-Dan

HO93LX302 · May 9, 2004

Try adjusting the throttle body plate.. turn the adjusting screw a little bit at a time.. The plate could be open more then it should be

88stangmangt · May 9, 2004

tps?????????

HISSIN50 · May 9, 2004

after hookin it back up, you might want to disconnect the battery, turn on the headlights, and then re-hook and run it. it might need to relearn some stuff (some computers like this, and some incorrigible ones dont care) if the IAC is functioning better now than before. worth a try, i think.
good luck.

5.0Droptop · May 9, 2004

HISSIN50 said:
after hookin it back up, you might want to disconnect the battery, turn on the headlights, and then re-hook and run it. it might need to relearn some stuff (some computers like this, and some incorrigible ones dont care) if the IAC is functioning better now than before. worth a try, i think.
good luck.

I agree. I would Reset the idle and tps and reset the eec afterwards. Set the idel when car is at operating temp..... with the iac unplugged the motor rpms should drop but it shouldnt die, if it dies the idel is to low.... so turn the screw in some and try again. get it to idel with out surge with the iac unplugged, then plug in the iac and set the tps to .95-.98 and reset the eec.

sweet93hatch · May 9, 2004

Dude, did you figure out what the hell is going on with your ride. Mine is doing the EXACT same thing. It's pissing me off to no end. Let me know if you fixed the mother. Thanks.

BlackVert · May 9, 2004

my 96 was behaving that way and the iac was sticking open. cleaning it helped a little but it only lasted a few days. then it started sticking closed too. after i got a new one ($45 at autozone) the problem went completely away.

sweet93hatch · May 9, 2004

I put a new one on, reset the computer and it surges like a MF. Starts out at a little over a grand and then blasts up 3000 all on its own. I was putting air in my tires at the gas station and left her running. It sounded like it was ready to launch on the next yellow and I wasn't even in it. You should have seen the look on peoples faces.

BlackVert · May 9, 2004

sweet93hatch said:
I put a new one on, reset the computer and it surges like a MF. Starts out at a little over a grand and then blasts up 3000 all on its own. I was putting air in my tires at the gas station and left her running. It sounded like it was ready to launch on the next yellow and I wasn't even in it. You should have seen the look on peoples faces.

i can't imagine how that much air could be getting through the iac. it really sounds like you must have a vaccuum leak somewhere. does it ping when accelerating? got a check engine light? what happens if you completely block off the air to the iac?

one way to find a vaccuum leak is to spray carb cleaner at different possible sources while the engine is idling. the idle will change if you spray near the leak.

re your other thread: i have heard of people taking out the iac and controlling the idle with the throttle position, but to me it seems like the computer would get confused about it...

djk8705 · May 9, 2004

well after playing with the THrottle Plate screw I was able to get the Idle down to 1000 rpms... it was idleing around 900rpms b4 all this. The problem is tho that now when i take my foot OFF the gas... and i press in the clutch the RPMS go up a few hundred ... and the rpms sit at 2200 till i slow down a lot then they go to around 1500.. then i stop completely then they go to 1000... Any more ideas? I cudnt get the TPS to work with me.. shud i try a new TPS or a new IAC?

Thanks
Dan

BlackVert · May 9, 2004

djk8705 said:
well after playing with the THrottle Plate screw I was able to get the Idle down to 1000 rpms... it was idleing around 900rpms b4 all this. The problem is tho that now when i take my foot OFF the gas... and i press in the clutch the RPMS go up a few hundred ... and the rpms sit at 2200 till i slow down a lot then they go to around 1500.. then i stop completely then they go to 1000... Any more ideas? I cudnt get the TPS to work with me.. shud i try a new TPS or a new IAC?

Thanks
Dan

yes, try a new iac. that was exactly my behavior until i put in the new iac. cleaning it maybe helped a little, but not much and not for long. they are like $45 (at least for the 96) at autozone.

sweet93hatch · May 9, 2004

I bought one at advance auto and no dice. Still have the problem. Did you do anything other than install it?

dvs bullet · May 9, 2004

sweet93hatch said:
I bought one at advance auto and no dice. Still have the problem. Did you do anything other than install it?

Dude check your vacuum

slick88GT · May 9, 2004

I had this problem a while back and it turned out to be my lower intake gasket was leaking. Try the carb cleaner idea, that's how I pinpointed mine, just spray it around where the upper meets the lower and where the lower meets the heads, if idle drops while you are spraying then you have a leak.

sweet93hatch · May 9, 2004

I don't have a vac gauge.

HISSIN50 · May 10, 2004

they cost a few bucks. worth it! you should have 15-20 inches at idle. good luck.

djk8705 · May 10, 2004

where do you hook up a vacccmu guage? also I did remove the smog and i capped two vaccume lines. But if they are capped there shudnt be a problem right? Also did advanced auto take back the IAC if it didnt work? Thanks

-Dan

sweet93hatch · May 10, 2004

I didn't try to return it. For $45 I figure might as well leave it on.

sweet93hatch · May 10, 2004

Vac Gauge

Where and how do you install a cheap vac gauge to see whats goin on?

jrichker · May 10, 2004

sweet93hatch said:
Where and how do you install a cheap vac gauge to see whats goin on?

See Autozone for the gauge. The vacuum tree is on the firewall just above the LH side of the upper intake. It has a spare port where you can connect the vacuum gauge.

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