TBI 350 Target Idle Speed

[maronielb]

Hi guys, im in desperate need of help with my 93 silverado that has a 5.7L TBI motor, I have a high idle issue ive been chasing for a couple weeks now. I have done a full rebuild on the TB along with new injectors, new intake to TB gasket, New coolant temp sensor (scanner verified that its reading correctly) New idle air control value (yes i went through the calibration process) Adjusted TPS sensor to .59V. timing is set at 0 and there are no vacuum leaks but the truck still idles at 1k. So i decided to purchase an OBD1 scanner that shows live data i hooked up the scanner and i can see that the idle req is set at 1000 rpm so im starting to think that my computer is demanding a 1000 rpm idle and no mater what i do once its fully warmed up it idles at 1000 rpm in neutral (i have a 5 speed). So with all that being said i did research and found the BIN and XDF files for my truck and downloaded them and im able to view everything in tunerpro RT. My question to you guys is what perimeters does the computer use to determine idle speed? is it possible for the idle command to be set at 1k in the reman computer? my BCC code is AZDR which is the correct one for my truck and i opened up my computer to verify that is has the correct chip and it does. the previous owner had the computer changed with a reman one but i dont think that matters as the chip inside is still an AZDR. when i view the target idle rpm vs coolant temp in tunerpro for the AZDR bin and $9A XDF file i downloaded i see that when the coolant temp is 195 my idle should be between 650-700 but its not so thats why i want to know what perimeters are used to determine idle speed because obviously its not just the coolant temp.

[MO LS Noobie]

Throttle is open (.73V). Throttle 53%. What is the IAC value?

[TriumphR3]

Throttle is open (.73V). Throttle 53%. What is the IAC value?

Suggests the manual throttle setting may not be set right. Maronielb have you done the manual throttle set procedure?

[maronielb]

What is the manual throttle set procedure? is that the one where you remove the cap and adjust the idle screw on the TB? if so no i havent and im not willing to mess with that, its set from the factory and is not suppose to be messed with.

[TriumphR3]

What is the manual throttle set procedure? is that the one where you remove the cap and adjust the idle screw on the TB? if so no i havent and im not willing to mess with that, its set from the factory and is not suppose to be messed with.

Ok, with all due respect, I beg to differ with you. 99% of the mechs that deal with TBI understand that at some point you have to set/adjust the manual setting. Especially if it has been rebuilt. Anyway, here is the procedure. Oh and what did your IAC value read?

https://www.gmcmi.com/wp-content/upl...alibration.pdf

[MO LS Noobie]

https://www.gmcmi.com/wp-content/upl...alibration.pdf[/QUOTE]

This is good info.

[maronielb]

That picture was taken before i adjusted the TPS to .59V IAC counts fluctuate between 5-10

[MO LS Noobie]

That picture was taken before i adjusted the TPS to .59V IAC counts fluctuate between 5-10

If your TPS and IAC are as stated, could be vacuum leak, especially check brake booster.

Desired idle is 650, that is what it is shooting for. You are getting more air somewhere. What are your block learn and integrator fuel trims?

[maronielb]

how would i check the brake booster? and yes i agree 650 sounds like the perfect idle speed. i have no idea what a block learn it or integrator fuel trims. i dont think my scanner shows those. i will post a poc tommorow with everything that my scanner shows.

[MO LS Noobie]

Pinch off hose going to Booster, this works for any regular, soft, rubber hose. There should be no change in idle speed, or fuel trims. Also test any vacuum lines to carbon canister, HVAC system, or anything else vacuum operated.

Block learn/integrator are the terms GM used for fuel trims, long/short term before OBD2. 128 equals 100%, or 0 trim. Below 128 is taking away fuel, above is adding fuel. Anything within 10% is considered normal.