GM TBI question

Mace

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Sitting here looking at a GM TBI un it and wondering... I can see the TPS (throttle posistion sensor) And figure out what it exactly is but WTF is the secondary sensor on the TBI body??? Is it the air temp sensor???


I'll try to get a pic. The TBI unit is at home right now.

Okay, try this pic.

The TPS is at the end of the butterflies the other sensor is in the middle left hand side of this pic.

 
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Gumby

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To the left of the TPS? Thats the IAC - Idle Air Control motor.

Air comes in just to the left of the injector tower, passes by a pintle controlled by that motor, and goes under the throttle plate.
 

zebrabeefj40

 
 
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If it's just above the TPS in your picture: Idle Air Control motor. Opens and shuts depending on how much air the motor thinks it needs.

HTH,
Nick
 

Mace

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And apparently something that MEgasquirt does not need then..

Wonder how to plug it off :)
 

rusty_tlc

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Mace said:
And apparently something that MEgasquirt does not need then..

Wonder how to plug it off :)
Do you want to remove the sensor or just cap the connector?
 

Mace

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Not sure, MS seems to be confuused on which wires to use for what.. It goes back and forth saying yes or no on the IAC motor,.,.,.
 

rusty_tlc

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I don't know how you would block the sensor opening if you removed that but you could just get a mateing plug from the junk yard, cut the back side off and fill it with rtv. That would weather seal the sensor connections so you could use later it if you had to. I'm guessing it uses the newer weather proof (PITA) connectors.
 

Texican

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WTF keeps the RPM constant without the IAC?
On the OEM TBI when the motor starts to load, the IAC opens and lets more air in.
 

Mace

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No idea. but it works so...
 
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Mace,

Sorry for joining this post late... What are you planning over there? I take it that this is a TBI for a SBC. Where did you get the TBI and computer? Is this a kit, or are you putting together yourself? Have you had it in action yet?
 

Mace

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this is a GM tbi on a 2F (later to be turbocharged) running a Megasquirt computer.


Anyone have a need for a V6 TBI distributor and coil???
 
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I blocked mine off with the IAC itself. Fully extend the shaft and install it.

If you just plug the mounting threads on the TBI body, you will be permanently in the IAC's "wide open" position. This is because the IAC's plunger is what blocks or meters the additional air flow. For the MegaSquirt, I suppose you could leave the TBI's IAC mounting hole open so long as the interior "plunger hole" is plugged.
 
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