Random High IAC counts and idle

[B52Bombardier1]

I'd check the continuity of the temperature sensor wiring / connector and maybe put in a new temperature sensor if the cost wasn't much.

Rick

[chris989]

I'd check the continuity of the temperature sensor wiring / connector and maybe put in a new temperature sensor if the cost wasn't much.

Rick

Rick,
Thanks for the reply, Are you thinking if it had no connection/fault/short it might default to the -8C setting and through a ton of IAC?

When data logging i have never seen the temp deviate from normal operation.


Pictures are in this order
Park 25
park 103
after restart
flags
25park.PNG103 park.PNGafter restart.PNGflag data.PNG

I just realized Park/neutral flag is not checked. that might account for 25 IAC?

[sturgillbd]

Do you have the park/neutral switch connected to the ecm? Do you also have a speed sensor connected and the ecm able to see the vehicle speed? Either of those signals being absent can cause a high idle after coming to a stop. A engine stop/restart resets the IAC position.

[tayto]

any play in the throttle shaft?

[chris989]

any play in the throttle shaft?

I bought a TBI from this place when I rebuilt the motor/driveline ~5 years ago.

https://www.sprperformance.com/

The injectors that came with it failed after a year. The pedal always feels stiff off idle even after replacing the cable.
In the past I have pushed and pulled on the shaft while the truck was running thinking if there was play i could affect the rpm but it never made a difference.

If the shaft was loose it would just idle high? not add the IAC counts?

[chris989]

I just replaced the park/neutral switch again because i had no reverse lights. It wasn't that old. It has always been hooked up.

The truck is an 89 and came with the 400 turbo. It has the little green box behind the dash. It is no a 4l80 using a MSD atomic controller.

When i drive the truck next I will run ALDL and check for speed data.

[tayto]

Yes I have had throttle bodies where the shaft is loose and causes high or surging idle. i'm 99% sure SPR rebuahes all their units so I wouldn't worry there. FWIW, a '7427 pcm (or '7060) would have controlled your TBI and 4L80E.

[chris989]

I have the $4F mask. At the time i was not confident about installing and possibly repinning a different ECU. If this continues i might try going with a different unit.

I have a CJ build i can use the MSD with.

[chris989]

I dislike unsolved threads so i wanted to post, It has been a month and the truck has been running perfect and not one instance of high idle. I guess i will leave as is for now.

If I ever figure it out I will post the solution,
Chris