TBI years min idle speed info

[udidwht]

See those asking about this often. This is factory set and not recommended adjusting. But the following are the specs regarding 'Min idle speed setting'.



Looking at the 1994 service manual for 454 TBI under fuel systems (Section 4-4A) the 'Min idle speed' setting is... (Factory set screw)

For the 7,4L auto trans in Drive (wheels chocked) is 625 (+-25rpm) Closed loop. Reset the IAC closed and disconnect it. Once min idle is set reconnect the IAC.

Controlled Idle Speed is as follows:

454 7.4L in Drive wheels chocked 675 (+- 25rpm) IAC count 5-30 (Closed loop) at operating temp 196-222F (add 2 counts for every 1000ft above sea level

The 'controlled idle speed' is obtained by the control module positioning the IAC valve. A high/low coolant temp or AC clutch engagement may signal the control module to change the IAC counts.

IAC counts will be above 60 if idle is too low and zero counts if idle is too high. Things to check if so...

1. Vacuum leak/s

2. System too rich

3. TB obstruction

4. PCV issue

5. AC issue

[Eyez Open]

What you are posting is interesting. Marine tbi uses a cold temp fuel enrichment circuit. Works very well, almost flawless.

MEFI and obd are one program with minor variations lol one being open loop and the closed.
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