Another TBI question, High Idle - The 1947 - Present Chevrolet & GMC Truck Message Board Network

ryanmcb · 04-06-2011, 02:12 PM

I have a 88 Suburban, my first TBI motor. It idles high right now. It does not have a tach but I would guess about 1,300 rpm. Where should a TBI motor idle? How do I idle it down? Is there an adjuster screw or does the TBI idle run off a sensor?

This may sound basic for some of you but I am unfamiliar with the TBI. I will say that I have been very impressed. It is very responsive and runs smooth.

TruAggression · 04-06-2011, 02:45 PM

there is a idle screw but check coolant temp sensor first man i had that same issue...you can look through my previous post and check out all the answers and pictures of the stuff... but i say check that first then go from there...

ryanmcb · 04-06-2011, 02:51 PM

thanks TruAggression. That may be the cause. I did not know those two things are related. I am just going to replace that sensor and eliminate that possiblity.

Hulk Will Smash · 04-06-2011, 03:04 PM

Threre's a TBI conversion thread that has a ton of awesome info in it. Was a huge help to me getting my truck running right. Vac leak is a big source of high idle issues as well. I replaced the base gaskets on mine and it made a world of difference.

TruAggression · 04-06-2011, 03:21 PM

Yeah base gasket is another possible that I changed as well even the iac as well... Tbi is a fun motor to play with and yes I love how smooth it runs when it does run good...
Posted via Mobile Device

kelsfine69 · 04-06-2011, 04:29 PM

yup base gasket first thing Id check

ryanmcb · 04-06-2011, 04:58 PM

Ok, I will do the base gasket as well. I actually found the thread you guys are talking about. That has some awesome information, thank you. I have enough to keep me busy for an entire weekend. I will let you all know what happens.

87 V20 Scottsdale · 04-06-2011, 08:00 PM

Check your O2 sensor, if it is faulty then the truck will run in a limp mode with a preset idle (like when you first start the truck in the morning).

SmittySmith · 04-06-2011, 08:03 PM

You can use some WD40 and spray the base of your throttle body to check for the gasket leaking, if the idle drops when you spray the base, then replace the gasket... just a quick way to check it before pulling it...

pig rig · 04-06-2011, 09:46 PM

the coolent temp will kinda act like a choke it will add fuel when its cold
and its the one right below the thermostat the one that in the side of the head is only for the gauge the way I understand it

04-06-2011, 02:12 PM	#1
ryanmcb Registered User Join Date: Dec 2010 Location: Grantsville, Ut Posts: 164	Another TBI question, High Idle I have a 88 Suburban, my first TBI motor. It idles high right now. It does not have a tach but I would guess about 1,300 rpm. Where should a TBI motor idle? How do I idle it down? Is there an adjuster screw or does the TBI idle run off a sensor? This may sound basic for some of you but I am unfamiliar with the TBI. I will say that I have been very impressed. It is very responsive and runs smooth. Last edited by ryanmcb; 04-06-2011 at 02:13 PM.

04-06-2011, 02:45 PM	#2
TruAggression Registered User Join Date: Aug 2010 Location: Las Vegas,NV Posts: 118	Re: Another TBI question, High Idle there is a idle screw but check coolant temp sensor first man i had that same issue...you can look through my previous post and check out all the answers and pictures of the stuff... but i say check that first then go from there...

04-06-2011, 02:51 PM	#3
ryanmcb Registered User Join Date: Dec 2010 Location: Grantsville, Ut Posts: 164	Re: Another TBI question, High Idle thanks TruAggression. That may be the cause. I did not know those two things are related. I am just going to replace that sensor and eliminate that possiblity.

04-06-2011, 03:04 PM	#4
Hulk Will Smash Registered User Join Date: Apr 2006 Location: Huntington Beach, CA Posts: 492	Re: Another TBI question, High Idle Threre's a TBI conversion thread that has a ton of awesome info in it. Was a huge help to me getting my truck running right. Vac leak is a big source of high idle issues as well. I replaced the base gaskets on mine and it made a world of difference. __________________ '87 R30 Crew Cab Dually It's 11 PM, do you know where your IAC pintle is?

04-06-2011, 03:21 PM	#5
TruAggression Registered User Join Date: Aug 2010 Location: Las Vegas,NV Posts: 118	Re: Another TBI question, High Idle Yeah base gasket is another possible that I changed as well even the iac as well... Tbi is a fun motor to play with and yes I love how smooth it runs when it does run good... Posted via Mobile Device

04-06-2011, 04:29 PM	#6
kelsfine69 18 Till I Die Join Date: Mar 2005 Location: Alberta, Canada Posts: 1,522	Re: Another TBI question, High Idle yup base gasket first thing Id check __________________ 2011 GMC Acadia 1969 GMC BBC LS7 2007 GMC Crew Duramax 1987 Camaro Iroc 350 Tuned Port Injection 42000Km 1987 Chevrolet Silverado 350 TBI 1987 Chevrolet Silverado 350 TBI(yes 2) Take me drunk, I'm too home...

04-06-2011, 04:58 PM	#7
ryanmcb Registered User Join Date: Dec 2010 Location: Grantsville, Ut Posts: 164	Re: Another TBI question, High Idle Ok, I will do the base gasket as well. I actually found the thread you guys are talking about. That has some awesome information, thank you. I have enough to keep me busy for an entire weekend. I will let you all know what happens.

04-06-2011, 08:00 PM	#8
87 V20 Scottsdale Registered User Join Date: Jul 2010 Location: Georgetown, KY Posts: 183	Re: Another TBI question, High Idle Check your O2 sensor, if it is faulty then the truck will run in a limp mode with a preset idle (like when you first start the truck in the morning). __________________ Andrew 1987 V20 Scottsdale 383 TBI, SM465, NP208, 14FF, 4.10 1988 C1500 Scottsdale 305, 700R4, 3.08 1986 K30 Custom Deluxe 6.2, SM465, NP205, 14FF, 4.10

04-06-2011, 08:03 PM	#9
SmittySmith '82 GMC Sierra Classic Join Date: Aug 2005 Location: Oklahoma City Posts: 82	Re: Another TBI question, High Idle You can use some WD40 and spray the base of your throttle body to check for the gasket leaking, if the idle drops when you spray the base, then replace the gasket... just a quick way to check it before pulling it...

04-06-2011, 09:46 PM	#10
pig rig Registered User Join Date: Feb 2009 Location: washington the state Posts: 730	Re: Another TBI question, High Idle the coolent temp will kinda act like a choke it will add fuel when its cold and its the one right below the thermostat the one that in the side of the head is only for the gauge the way I understand it __________________ my sports car rolls on six wheels only because I'm to fat to get in and out of new corvette http://hubgarage.s3.amazonaws.com/ph...ped_detail.JPG



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