I have an 89 iroc z with a 305 TPI. I need to set my timing but I don't have the emissions sticker and every book from chiltons to hayes says refer to the sticker. Does anyone know what my timing should be?

6 degrees before top dead center with the est connector disconnected I believe.

ESC module is for the knock sensor, to set the timing disconnect the, "Set Timing" weather pack single wire quick disconnect connector (tan wire with white strip) located hanging out of the wire loom just above the HVAC housing.

I always thought the est connector (aka Electronic Spark Timing) was the "Set Timing" connector. Learn something new everyday!

Things you will need:
You MUST definitely use a timing light to adjust your timing correctly. You definitely CAN'T do this correctly just by turning your distributor and guessing.

If you just guess when you retard the timing so far that you can't hear any pings doesn't mean anything. Most of the time you won't be able to hear any ping/knock, but your knock sensor will.

The only way a timing adjustment does make sense is: Adjust it using a timing light and hook up a scanner/winaldl and check for knock counts under all driving conditions. If the engine does knock/ping, retard it in 2* increments.

A 9/16" or 14mm open end wrench.

To adjust your timing:



Warm up your engine to normal operating temperature. Shut off your engine.
Disconnect the tan wire with a black stripe that comes out of the harness near the heater box. It is a big weatherpack connector, you can hardly overlook it.
Connect your timing light to the battery (check polarity), connect the inductive pickup of the timing light to your #1 cylinder as near to the spark plug as possible without toasting it with your exhaust manifold/header.
Start your engine and ignore the SES light coming up.
Point your light at the timing mark and check your setting. Watch the timing light's wires. If they come in contact with the drive belt/accessories while the engine is running you could get seeriously injured.
If you can't read your timing mark because of rust/dirt, stop your engine and clean it using sanding paper (PITA).

If you still can't read what's on your timing mark: Assuming you are standing in front of your car, facing the engine, the "valley" of the biggest of the v-shaped notches should be zero degrees.

The Vs are upside down when you look at them from the front of the car.

The next peak (pointing towards you) to the left of the big V is 4* advanced, one more peak to the left is 6* and so on in 2* increments.

Accordingly, the one and only peak to the right of the big V is 2* retarded.

Check for the sticker in your engine compartment for the correct setting and compare it to your reading. If it matches you are fine.
Proceed with step 10.

If it does not match or you want to advance/retard your timing for other reasons get a 9/16" or 14mm open end wrench and proceed with the next step.

Remove your air cleaner and approach your engine from the driver's side. Locate the distributor hold-down clamp and screw.
Insert your wrench in the opening between the ignition coil and the distributor from the driver's side.

Loosen the distributor hold-down clamp just so much, that you can turn your distributor by hand with little effort (Should be a 1/4 to 1/2 turn of the screw, maybe a little more). There my be several other ways to loosen the distributor clamp but this one worked for me. Maybe you can find an easier way, using other tools.
Now point your timing light at the timing mark again and rotate your distributor slighty.
Turning it counterclockwise advances the ignition, turning it clockwise retards it.

If you have your setting as desired, tighten the distributor hold-down clamp.

Recheck your setting after that.

When it is still fine, shut off your engine, reconnect the tan wire, disconnect your timing light and disconnect the negative battery cable for a few minutes. This will erase the error code that came up when you disconnected the tan wire.
Reinstall your air cleaner and reconnect your negative battery cable.
Test drive your car using a scanner or to check for pings/knocks.

Yep, you're right, that's what it's called, the EST (Electronic Spark Timing). The ESC (Electronic Spark Control) is part of the Knock Sensor system.

GM confuses lots of folks in the way it names things. Think about MAT and MAF as another example of confusing naming.

Jake

West Point ROCKS! Nation's TOP COLLEGE per Forbes Magazine!! Graduation
Day Parade 20 May 2010!!!

[quote=JakeJr;4380846]Yep, you're right, that's what it's called, the EST (Electronic Spark Timing). The ESC (Electronic Spark Control) is part of the Knock Sensor system.

GM confuses lots of folks in the way it names things. Think about MAT and MAF as another example of confusing naming.

Jake

I not sure when the "STC" (that's my acronym for "Set Timing Connector.") was was first used. It is actually located on the By-pass wire from the ICM to the ECM, or vice-versa.
But, EST and By-pass are 2 separate Ignition Control Module (ICM) signals via a 4-wire connector.
The 4 signals are:

1. EST
2. Reference
3. By-pass (advance disabled by disconnecting the STC)
4. Distributor ground

The by-pass line disables ECM control of the timing signal, GM put a quick disconnect, "Set Timing Connector" on this line and locating it in an easily accessible area.

Out of curiosity why do you call the By-pass quick disconnect "EST" when the electrical diagrams refer to it as "Set Timing Connector?"

I've always thought of it as "EST" Electronic Spark Timing aka set timing wire and the "ESC" as Electronic Spark Control which is the knock sensor circuit?

simple....with the tan wire w/ white strip (black connector) located near heater assembley on passenger side of engine bay near firewall.....coming out of large wire loom, and the check engine light should come on....set timing to 6 degrees for factory setting.