87 tbi idles way to high - The 1947 - Present Chevrolet & GMC Truck Message Board Network

stan79chevy · 09-21-2004, 02:43 PM

a buddy of mine just got his truck running again and it idles at about 2500rpm. how do you turn that down. its an 87 350b tbi completely stock 4x4. it ran good but had a leaky gas tank. it sat for 3mos then he replaced the gas tank and now has this problem. how do you turn the idle down on a tbi? or is it a sensor or something?

thanks
stan

Jonboy · 09-21-2004, 02:57 PM

I would look at the idle stop screw, then check the TPS. Also, make sure there isn't a vacuum leak or something similar.

1987SierraClassic · 09-21-2004, 03:01 PM

The computer should take care of the idle. Check the IAC (Idle Air Controller) to make sure it isn't stuck. It's on the passengers side of the TBI toward the firewall. It is a round device a little bigger than your thumb (well, mine anyway) with a hex nut at the base and has a 4-wire harness connected to it.
Also, if the gasket under the TBI goes bad, it may cause this condition as well, I'd check that first, then check for vacuum leaks. You should get a check engine light if the IAC is bad. (Code 35)

My '87 sits for extended periods and I've never had an idle problem.

Hope this info helps!

stan79chevy · 09-27-2004, 10:24 PM

so we took the dash apart and found that the bulb was bad. hes going to replace the gasket this week and hopefully it will work.

thanks
stan

1987SierraClassic · 09-28-2004, 08:35 AM

Let us know how you make out!

09-21-2004, 02:43 PM	#1
stan79chevy Registered User Join Date: Sep 2003 Location: COVINGTON GEORGIA Posts: 477	87 tbi idles way to high a buddy of mine just got his truck running again and it idles at about 2500rpm. how do you turn that down. its an 87 350b tbi completely stock 4x4. it ran good but had a leaky gas tank. it sat for 3mos then he replaced the gas tank and now has this problem. how do you turn the idle down on a tbi? or is it a sensor or something? thanks stan __________________ 79 chevy k20 350/350/205/D44/14bFF 4.56 gears rock LWB pimer black 01 S-10 ZR2 extended cab 4.3/4L60E/233 3.73 gear 31" DICK CEPEK CRUSHERS

09-21-2004, 02:57 PM	#2
Jonboy Slots go on anything! Join Date: May 2003 Location: Richardson, TX Posts: 5,957	I would look at the idle stop screw, then check the TPS. Also, make sure there isn't a vacuum leak or something similar. __________________ 1974 Jimmy- 5.3/4L80e/NP241

09-27-2004, 10:24 PM	#4
stan79chevy Registered User Join Date: Sep 2003 Location: COVINGTON GEORGIA Posts: 477	the check engine light dosent come on so we took the dash apart and found that the bulb was bad. hes going to replace the gasket this week and hopefully it will work. thanks stan __________________ 79 chevy k20 350/350/205/D44/14bFF 4.56 gears rock LWB pimer black 01 S-10 ZR2 extended cab 4.3/4L60E/233 3.73 gear 31" DICK CEPEK CRUSHERS

09-21-2004, 03:01 PM	#3
1987SierraClassic Registered User Join Date: Sep 2004 Location: Buxton, ME Posts: 91	The computer should take care of the idle. Check the IAC (Idle Air Controller) to make sure it isn't stuck. It's on the passengers side of the TBI toward the firewall. It is a round device a little bigger than your thumb (well, mine anyway) with a hex nut at the base and has a 4-wire harness connected to it. Also, if the gasket under the TBI goes bad, it may cause this condition as well, I'd check that first, then check for vacuum leaks. You should get a check engine light if the IAC is bad. (Code 35) My '87 sits for extended periods and I've never had an idle problem. Hope this info helps!

09-28-2004, 08:35 AM	#5
1987SierraClassic Registered User Join Date: Sep 2004 Location: Buxton, ME Posts: 91	Let us know how you make out!



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