TBI setting/adjustment

[87jimmy]

Can anyone tell me how to adjust the idle on an 87 fuel injected 350. The truck is idling about 1500 or so. I hear that it can be adjusted by moving the throttle position sensor and I do not hear or see any vacuum leaks

 

[chev3600]

Here is the info I found when searching for the same thing last year, worked well for me, but be sure you don't have another issue causing the high idle first.

I would adjust the minimum idle to about 600 rpm.

To do that

1.)Drill out the pressed in cap over the adjustment screw and obtain the proper torx screw driver
2.)Warm up the truck and shut it off
3.)Jumper A-B on the ALDL connector
4.)Wait 30 seconds while the IAC closes
5.)Remove the IAC connector on the TBI
6.)Start the truck
7.)Adjust the idle speed to 600 rpm
8.)Shut-off the truck
9.)Reconnect the IAC and remove the jumper.

 

[87jimmy]

what is the ALDL

 

[chev3600]

aldl

It is the data link connector, diagnositic connector or whatever it may also be called. Just like on the newer cars you can plug a computer into this plug to retreive codes and info. Its under the dash usually on the drivers side. black plug with two rows. about 16 pins. If you look close some are labelled with the pin number really small. Or google search OBD1 (on board diagnositic version 1)

 

[Matthew]

Here is the info I found when searching for the same thing last year, worked well for me, but be sure you don't have another issue causing the high idle first.

I would adjust the minimum idle to about 600 rpm.

To do that

1.)Drill out the pressed in cap over the adjustment screw and obtain the proper torx screw driver
2.)Warm up the truck and shut it off
3.)Jumper A-B on the ALDL connector
4.)Wait 30 seconds while the IAC closes
5.)Remove the IAC connector on the TBI
6.)Start the truck
7.)Adjust the idle speed to 600 rpm
8.)Shut-off the truck
9.)Reconnect the IAC and remove the jumper.

If you do it like this your idle will all be screwed up the way to do it is
1. CHECK YOUR CAM TO DISTRIBUTOR TIMING 100% OF TBI ENGINES FROM GM WAS SET FROM THE FACTORY WRONG!!!! The plug in connectors should face straight back if not your cam timing is out. Set ignition timing to 6 degrees with the little brown wire unpluged. This should be done with truck at FULL OPERATING TEMP.

2. now check your idle speed agin 9 times out of ten it with be exactly at 650rpm hot idling THIS IS MANUFACUER SPEC.

If it is not running at that speed then continue with 3-

3.)Jumper A-B on the ALDL connector

4.)Wait 30 seconds while the IAC closes

5.)Remove the IAC connector on the TBI

6.)Start the truck

7.)Adjust the idle speed to 400rpm

8.)Shut-off the truck

9.)Reconnect the IAC and remove the jumper.