99 LS1 trans am tuning questions??

[weston]

hello, im having some issues with my car after a well known tuner, tuned my car. ive tried contacting him multiple times about the issue but im guessing he got his money and ran. anyway im having some trouble with idle hang and as well as when pressing in the clutch and coming to a stop the rpms drop down below desired rpms. ive scanned the car with little knowledge i have and from what im seeing is the car is running extremely rich and my IAC counts/steps are very high 160-180 range. from what ive read you have to adjust the set screw on the throttle body to fix the problem however im not sure if by adjusting the screw if it would mess with my tune. im going to attach a scan log if anybody would mind looking at it for me. the car seems to run better with the ac on with the ac off the idle sounds like its misfiring. any feedback is appreciated Thanks.


99 LS1 M6: 231/234 cam along with supporting mods, 243 stock heads, ls6 intake manifold stock throttle body

[jpliss]

Adjusting the screw wont mess with the tune, however the correct way to set the throttle angle on a cable car is to perform an iac reset.

put key in ON position
Unplug IAC
Turn key off

Now start the car and you most likely will need to hold throttle to keep car running, set the base idle so the engine is just idling, then turn key off.

Wait 30 seconds

Turn key on, leave on for 30 seconds. You should see a SES light now too.

Turn key off.

Plug IAC back in.

Turn key on.

If you can, verify with a scanner ( with key ON only, not car running ) that with your foot off the gas it's reading 0%, and at WOT it's reading 100%.

Your done.

[edcmat-l1]

Adjusting the screw wont mess with the tune, however the correct way to set the throttle angle on a cable car is to perform an iac reset.

put key in ON position
Unplug IAC
Turn key off

Now start the car and you most likely will need to hold throttle to keep car running, set the base idle so the engine is just idling, then turn key off.

That's not correct. When you cycle the key on the IAC opens to allow additional airflow for startup. It does not close the IAC.

Back in the day, like WAY back in the day, we used to hold them up off idle while running which caused the IAC to close. Then unplug it while you're holding it off idle. When you let it come back to idle they would normally idle very low or stall. That was an actual OBD1 procedure if you did not have the Thexton IAC motor actuator.

[Alvin]

hello, im having some issues with my car after a well known tuner, tuned my car. ive tried contacting him multiple times about the issue but im guessing he got his money and ran. anyway im having some trouble with idle hang and as well as when pressing in the clutch and coming to a stop the rpms drop down below desired rpms. ive scanned the car with little knowledge i have and from what im seeing is the car is running extremely rich and my IAC counts/steps are very high 160-180 range. from what ive read you have to adjust the set screw on the throttle body to fix the problem however im not sure if by adjusting the screw if it would mess with my tune. im going to attach a scan log if anybody would mind looking at it for me. the car seems to run better with the ac on with the ac off the idle sounds like its misfiring. any feedback is appreciated Thanks.


99 LS1 M6: 231/234 cam along with supporting mods, 243 stock heads, ls6 intake manifold stock throttle body

The IAC is far too open to be able to control idle effectively. The throttle body likely needs to be adjusted.. Before you follow these steps use the scanner to control the IAC positon. Move it max high or low and see that the idle changes. It seems like IAC's last about 15-20 years because I'm running into bad ones pretty often.

Here is the instructions we send out to setup a throttle body.

https://www.pcmofnc.com/2021/03/05/i...throttle-body/