Tbi 5.7 ignition timing

eran tomer · Jul 19, 2022

When checking ignition timing on tbi does it matter if the air cleaner is installed or not?

Schurkey · Jul 19, 2022

No. The distributor does not know if the air cleaner is in place.

Therefore, most folks will remove the air cleaner to make accessing the distributor easier.

What DOES make a difference is the EST wire that has to be unplugged to set timing properly on a TBI vehicle.

eran tomer · Jul 19, 2022

the distributor doesn't know, but maybe the ecu knows according to the air flow and changes the timing?

PlayingWithTBI · Jul 19, 2022

eran tomer said:
the distributor doesn't know, but maybe the ecu knows according to the air flow and changes the timing?

Nope, when you disconnect the EST wire, it eliminates the ECM/PCM controls of timing.

highwaystar · Jul 21, 2022

The est wire is under the glove box in my '94, under hood in other years?

thinger2 · Jul 21, 2022

highwaystar said:
The est wire is under the glove box in my '94, under hood in other years?

Yep. It was a mid production 94 change.
It caused a bunch of problems for the GM techs because nobody told them about it.
There is a TSB ( Technical Service Bulliten) about it
So some early 94 trucks still have the EST wire on the firewall.
Later production has the wire in the cab next to the blower motor.

Tbi 5.7 ignition timing

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