Cleaned the IAB valve, now have 'sticking' throttle

Ford Vader · 05-15-2001, 10:20 AM

Hey guys. I was having a problem with my car occasionally stalling when I would come to an idle, its a stock '90 GT 5 spd. I tracked the problem down to the IAB valve so I removed it and cleaned it out thoroughly with carb cleaner. While I was at it I removed the throttle body and cleaned it and the egr spacer out. When I started the car I could tell immediately that there was a difference, the stalling problem is definately gone. But now the car idles higher (about 1000 up from 600) and when I rev the engine and let off of the gas and push in the clutch the rpm's don't fall back down right away, the rpm's drop slowly to about 1500 rpm and hang there for a little while, then finally come back down to about 1000 rpm. I checked for vaccum leaks and there are none. To test it I unplugged the IAB valve and ran the engine for a minute. It ran fine with the IAB valve unplugged, it idled around 600 - 700 rpm and the rpm's would drop immediately after letting off of the gas, so I know the problem is with the IAB valve. Should I just get a new one? I wanted to get some opinions on this before I got out and get one because they're $80 or $90. Is there anything else I should check? Thanks in advance for your help!

jimberg · 05-15-2001, 01:56 PM

Since your IAB wasn't working properly to begin with, reset your computer first to see if things change.

------------------
351W 89 Mustang GT Convertible

slo95 · 05-15-2001, 03:08 PM

$80 or $90 for the IAC? seems high, when I priced one it was 36 bucks.

Ford Vader · 05-15-2001, 03:25 PM

I did reset the computer yesterday, it didn't help. The only change was when I started the motor with the IAB valve unplugged. I checked with my local dealership and the IAB valve was something like $86...do you know where I can get it for less?

Thanks,
Mike

vande97 · 05-15-2001, 05:49 PM

hell, you could try autozone, or napa, they should have one for you or at least they could order one maybe. the only thing bad about going to a dealer is that you can count on them ripping you off for and extra 20 to 50$ on parts!

i had them same thing happen to me but i have not replaced mine yet it is really weird i can run the car like that and then shut if off then start it right away again then it idles perfect...go figure.Lol

jimberg · 05-15-2001, 05:58 PM

What did you do to reset the computer? Did you just disconnect the battery for a while and start driving it, or did you let it idle for a while?

------------------
351W 89 Mustang GT Convertible

Ford Vader · 05-15-2001, 06:09 PM

To reset the computer I followed a procedure that I found on the corral.net site. I unplugged the battery for about 30 minutes, then I unplugged the IAB valve, plugged the battery back in and started the car. At this point it said to set the desired idle using the throttle plate screw, but the car was already idling where at around 600 - 700 rpms. Then I turned off the car, plugged the IAB valve back in, started it and let it idle for 2 minutes with no accessories on, then turned it off, then started it again and let it idle for 2 minutes with all accessories on, then turned it off. They said that the computer would learn to idle at the rpm's that the car idled at with the IAB valve unplugged but it didn't work.
Is there another way I should reset the computer?
Also, this may be a really dumb question but...the car ran fine with the IAB valve unplugged. I didn't take it for a drive but I revved it in my driveway. Is it really neccesary to have the valve plugged in?

Thanks again!
Mike

jimberg · 05-15-2001, 11:36 PM

Okay, you were kind of doing two procedures at once. I suppose that's okay. Unless you have digital tach, or one that's really accurate in the car, the best way is to use the feeler guage method. This is the one that the service manual says to use. The method they used on corral.net is actually for the 6-cyl.

Back the throttle adjustment screw out until you can fit a .010" feeler gauge between the screw and the stop plate. Turn it in until you can feel a little resistance as you pull the feeler gauge out. Turn the adjustment scew another 1 1/2 turns. Disconnect only the negative battery cable for about 15 minutes. Put the cable back on and start the car. Idle with no accessories for 10 minutes. Turn off. Start. Idle with all accessories for another 10.

See how it runs then. If the car runs well with the IAB disconnected, that probably means the idle is set too high by the adjustment screw.

If this doesn't work, there probably is something wrong with the IAB.

------------------
351W 89 Mustang GT Convertible

05-15-2001, 10:20 AM	#1
Ford Vader Registered Member Join Date: Mar 2000 Location: Asheville, NC Posts: 10	Cleaned the IAB valve, now have 'sticking' throttle Hey guys. I was having a problem with my car occasionally stalling when I would come to an idle, its a stock '90 GT 5 spd. I tracked the problem down to the IAB valve so I removed it and cleaned it out thoroughly with carb cleaner. While I was at it I removed the throttle body and cleaned it and the egr spacer out. When I started the car I could tell immediately that there was a difference, the stalling problem is definately gone. But now the car idles higher (about 1000 up from 600) and when I rev the engine and let off of the gas and push in the clutch the rpm's don't fall back down right away, the rpm's drop slowly to about 1500 rpm and hang there for a little while, then finally come back down to about 1000 rpm. I checked for vaccum leaks and there are none. To test it I unplugged the IAB valve and ran the engine for a minute. It ran fine with the IAB valve unplugged, it idled around 600 - 700 rpm and the rpm's would drop immediately after letting off of the gas, so I know the problem is with the IAB valve. Should I just get a new one? I wanted to get some opinions on this before I got out and get one because they're $80 or $90. Is there anything else I should check? Thanks in advance for your help!

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05-15-2001, 01:56 PM	#2
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	Since your IAB wasn't working properly to begin with, reset your computer first to see if things change. ------------------ 351W 89 Mustang GT Convertible

05-15-2001, 03:08 PM	#3
slo95 Registered Member Join Date: Dec 2000 Posts: 168	$80 or $90 for the IAC? seems high, when I priced one it was 36 bucks.

05-15-2001, 03:25 PM	#4
Ford Vader Registered Member Join Date: Mar 2000 Location: Asheville, NC Posts: 10	I did reset the computer yesterday, it didn't help. The only change was when I started the motor with the IAB valve unplugged. I checked with my local dealership and the IAB valve was something like $86...do you know where I can get it for less? Thanks, Mike

05-15-2001, 05:49 PM	#5
vande97 Registered Member Join Date: Jan 2001 Location: okemos Posts: 205	hell, you could try autozone, or napa, they should have one for you or at least they could order one maybe. the only thing bad about going to a dealer is that you can count on them ripping you off for and extra 20 to 50$ on parts! i had them same thing happen to me but i have not replaced mine yet it is really weird i can run the car like that and then shut if off then start it right away again then it idles perfect...go figure.Lol

05-15-2001, 05:58 PM	#6
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	What did you do to reset the computer? Did you just disconnect the battery for a while and start driving it, or did you let it idle for a while? ------------------ 351W 89 Mustang GT Convertible

05-15-2001, 06:09 PM	#7
Ford Vader Registered Member Join Date: Mar 2000 Location: Asheville, NC Posts: 10	To reset the computer I followed a procedure that I found on the corral.net site. I unplugged the battery for about 30 minutes, then I unplugged the IAB valve, plugged the battery back in and started the car. At this point it said to set the desired idle using the throttle plate screw, but the car was already idling where at around 600 - 700 rpms. Then I turned off the car, plugged the IAB valve back in, started it and let it idle for 2 minutes with no accessories on, then turned it off, then started it again and let it idle for 2 minutes with all accessories on, then turned it off. They said that the computer would learn to idle at the rpm's that the car idled at with the IAB valve unplugged but it didn't work. Is there another way I should reset the computer? Also, this may be a really dumb question but...the car ran fine with the IAB valve unplugged. I didn't take it for a drive but I revved it in my driveway. Is it really neccesary to have the valve plugged in? Thanks again! Mike

05-15-2001, 11:36 PM	#8
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	Okay, you were kind of doing two procedures at once. I suppose that's okay. Unless you have digital tach, or one that's really accurate in the car, the best way is to use the feeler guage method. This is the one that the service manual says to use. The method they used on corral.net is actually for the 6-cyl. Back the throttle adjustment screw out until you can fit a .010" feeler gauge between the screw and the stop plate. Turn it in until you can feel a little resistance as you pull the feeler gauge out. Turn the adjustment scew another 1 1/2 turns. Disconnect only the negative battery cable for about 15 minutes. Put the cable back on and start the car. Idle with no accessories for 10 minutes. Turn off. Start. Idle with all accessories for another 10. See how it runs then. If the car runs well with the IAB disconnected, that probably means the idle is set too high by the adjustment screw. If this doesn't work, there probably is something wrong with the IAB. ------------------ 351W 89 Mustang GT Convertible