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73-87 Chevy _ GMC Trucks => Performance => Topic started by: Tazman on April 27, 2013, 01:11:49 pm

Title: Setting Idle on 220 TBI
Post by: Tazman on April 27, 2013, 01:11:49 pm

I was setting the idle on my 87 using info from my service manual and from this site.I had done the block ,unplugged the IAC and started the truck.Instructions say to set idle to 550 plus or minus 50,The instructions do not say whether to have the truck park or drive,thus I was not able to get the idle set.I will do it again with the truck in drive with brake set and someone in the seat holding the brake.My is this,will this work the way it is supposed to?Thanks 

Title: Re: Setting Idle on 220 TBI
Post by: VileZambonie on April 27, 2013, 01:25:42 pm

You shouldn't have to adjust your idle. Th ecm learns min iac. Why are you trying to adjust it? What's your tps voltage read?

Title: Re: Setting Idle on 220 TBI
Post by: Tazman on April 27, 2013, 03:48:01 pm

Yes I realized this (IAC) after I did the original post.The TPS is where it should but I may have a bad IAC.I did the block and had my wife turn the key to start (not run)while looked to wacth the IAC.I beleive it is supposed to close,it did not.Is it bad? Thanks

Title: Re: Setting Idle on 220 TBI
Post by: Tazman on May 07, 2013, 10:12:55 pm

Replaced the IAC ,truck idles great when warmed up or in gear but when first starting not really.First started in the morning the idle still fluctuates but when put in gear it is fine.The only thing I believe is left is a vacuum line but I really doubt that.Any help with this would be greatly appreciated. 

Thanks

Title: Re: Setting Idle on 220 TBI
Post by: Captkaos on June 11, 2013, 04:51:00 pm

Did you figure this out?  Fluctuates how?  surges or holds a high idle or?

Title: Re: Setting Idle on 220 TBI
Post by: Tazman on June 11, 2013, 08:00:17 pm

Surges at idle after start up,when I put it in gear it runs great.Been told it is leaking around the injector and when putting in gear the ecm takes over and it stops.Plan on rebuilding the TBI soon.
Thanks

Title: Re: Setting Idle on 220 TBI
Post by: Irish_Alley on June 12, 2013, 12:47:48 am

 idle surge can occur to a tbi by the IAC, EGR, EGR controller, MAP, temp sensor, vacuum leaks, O2 and tbi fuel pressure problems could be in the tbi itself or the fuel pressure regulator. but before you spend any money you can test/adjust the tps and iac
http://www.thirdgen.org/tpimod2

Title: Re: Setting Idle on 220 TBI
Post by: VileZambonie on June 12, 2013, 03:56:01 pm

Check for vacuum leaks at the base of the TBI unit. With the engine running, carefully mist some carb clean around the base and see if it changes the engine speed.