when checking timing

hey all,

on a 91 c1500 4.3L do I need to disconnect any vacume hoses or anything else when I check my timing? Or do i just do a straight hook up of +/- & #1 wire? I checked it today and it was totally wacked and way off of 0. It's running well, but I just happened to check.

thanks

hey all,

on a 91 c1500 4.3L do I need to disconnect any vacume hoses or anything else when I check my timing? Or do i just do a straight hook up of +/- & #1 wire? I checked it today and it was totally wacked and way off of 0. It's running well, but I just happened to check.

thanks

You have to disconnect the spark timing est bypass wire.
Then set base time and the hook wire back up and clear code and go.
And before you ask it is a single tan and black wire with a plug in connector on it.
Under heater core housing /or behind/under glove box in cab
When it is unplugged it will set code and turn on check engine light.
So clear codes / battery neg cable off and on will do it when done setting time
Also sometimes the EST wire is laying under carpet at/under heater core housing.
MT

You have to disconnect the spark timing est bypass wire.
Then set base time and the hook wire back up and clear code and go.
And before you ask it is a single tan and black wire with a plug in connector on it.
Under heater core housing /or behind/under glove box in cab
When it is unplugged it will set code and turn on check engine light.
So clear codes / battery neg cable off and on will do it when done setting time
Also sometimes the EST wire is laying under carpet at/under heater core housing.
MT

Is clearing the codes required on the 4.3? I have owned my 90 K1500 5.7 since new and I have never needed to clear the code after setting the timing. The check engine light always go off after reconnecting the EST wire. If you scan the ECM a few days later, no codes are stored.

Just curious if this is unique to the 4.3.

//2000CAYukon

Is clearing the codes required on the 4.3? I have owned my 90 K1500 5.7 since new and I have never needed to clear the code after setting the timing. The check engine light always go off after reconnecting the EST wire. If you scan the ECM a few days later, no codes are stored.

Just curious if this is unique to the 4.3.

//2000CAYukon

Some do and some do not.
If light gos out the no problem.
But sometimes it still helps let the pcm reset after tune up or adjustments..
MT

Some do and some do not.
If light gos out the no problem.
But sometimes it still helps let the pcm reset after tune up or adjustments..
MT

Thanks MT!

//2000CAYukon

thanks MT.

found the connector inside the enginie compartment.

Even though i can check it, there is nothing I can really do to adjust the timing is there? the 91's were not adjustable. I guess the only reason to know my timing is for time like when replacing the dist. shafts or chains i would think.

Is there anything I can do to adjust or fine tune the timing or will anything I do be adjusted back by the ECM?

I've never needed to check it in the past, I just happened to come across a brand new timing gun at the pawn shop the other day for only $4.95, so I thought i should pick it up..but it's not my old firebird.

thanks MT.

found the connector inside the enginie compartment.

Even though i can check it, there is nothing I can really do to adjust the timing is there? the 91's were not adjustable. I guess the only reason to know my timing is for time like when replacing the dist. shafts or chains i would think.

Is there anything I can do to adjust or fine tune the timing or will anything I do be adjusted back by the ECM?

I've never needed to check it in the past, I just happened to come across a brand new timing gun at the pawn shop the other day for only $4.95, so I thought i should pick it up..but it's not my old firebird.

I have the factory manuals for 1990 (which covers all engines) and the timing is adjustable. Disconnect the EST connector, loosen the hold down clamp on the dist, set the timing (by rotating the dist), tighten the hold down clamp and reconnect the EST.

//2000CAYukon

thanks yukon.

I thought that was the way, but i thought that the ECM then tries to adjust it back. I read where you said your manual covers all engines for 1990, does that cover the 91 4.3 as well. I don't think there was a change from 90-91

thanks yukon.

I thought that was the way, but i thought that the ECM then tries to adjust it back. I read where you said your manual covers all engines for 1990, does that cover the 91 4.3 as well. I don't think there was a change from 90-91

That is why you disconnect the bypass wire.
It sets the pcm in base time so you can addjust it.

Was it a single tan/black wire that you unplugged?
Where was it in engine compartment?