GTAman

iTrader: (2)

hey guys,

what is the correct idle speed in gear for a 1988 GTA with TPI 305 and 700-R4 with a holley 52mm throttle body? and can it be corrected by just turning the idle screw?

-Mark

robsgta

750 rpm and yes but moving your idle also changes the setting of your throttle position sensor.

92GTA

iTrader: (11)

600 in gear, 700 in park. 750 is not correct. Do not adjust it with the screw. You need to follow procedure and set the TPS, IAC, and idle using the screw as per the manual. If you need an idle different from factory like for a different cam, you need to change it in the PROM...

305RSlc

Actually, I believe it is 650rpm for auto transmissions in D.

here's some good reading.
https://www.thirdgen.org/techbb2/sho...threadid=93405

92GTA

iTrader: (11)

Sorry, I've got my stock 305/auto bin on my computer that says what I posted above is correct. He asked for 305/auto so I told him what my bin says. Stock bins don't lie...

rgarcia63

As others have stated:
Set the minumum air per manual don't forget to disconnect the timing connector, or you'll have to repeat.
This will be the TPS minimum voltage per manual.
Once you complete the procedure and restart the engine the ECM will control the idle speed to whatever is in memory.
The ECM uses other parameters to determine idle speed such as coolant temperature that's why it's important for the engine to be at normal operating temperature when setting the idle.

Good luck, and keep us posted.

327_TPI_77_Maro

iTrader: (8)

What? I have never heard that you disconnect the timing wire when you are setting the minimum airflow. Is this really the case? See the "setting minimum airflow" instructions here
https://www.thirdgen.org/newdesign/tech/tpimod2.shtml

If you disconnected the timing wire, your TPI will run at 8 degrees BTDC timing. If you actually set the minimum airflow at this low timing, then reconnected the timing connector (which with a warmed up engine will bring the base timing to 20-24 degrees BTDC) you'd have like a 2000 rpm idle, and the IAC wouldn't be able to do anything about it.

rgarcia63

I tried attaching and image of the instructions, but couldn't get it to display on the post, maybe someone else can confirm; it's worked for me.

Copyright © 2004 ALLDATA LLC
Idle speed is controlled by the ECM through the Idle Speed Control motor and is not adjustable. The minimum air rate is adjustable as follows.[list=1][*]Ground diagnostic terminal, turn ignition on, but do not start engine.[*]Wait 45 seconds for IAC to fully seat, then with ignition still on disconnect IAC connector. [*]Disconnect the distributor set timing connector. [*]Start engine and allow engine to go into "Closed Loop". [*]Remove ground from diagnostic terminal. [*]Adjust idle speed to specifications using throttle stop screw. [*]Turn ignition off and reconnect IAC connector. [*]Adjust TPS voltage if necessary: With ignition "ON" use a scan tool or 3 jumper wires to adjust TPS sensor to correct voltage specification. Tighten screws, then recheck reading to insure adjustment has not changed. [*]Start engine and check for proper idle operation.
[/list=1]

327_TPI_77_Maro

iTrader: (8)

Ah, I see how this would work -- I think the factory spec is 450 rpm minimum air flow, so when you reconnect timing wire and you gain ~12-14 degrees timing at idle, this will become close to the 600 rpm factory idle speed. I just set my minimum airflow w/ the timing connected to get me just barely under my target idle, so the IAC doesn't keep hunting because of my cam.