How to set timing on 1998 gmc sierra
The v-8's timing is supposed to be 0 degrees plus or minus 2 degrees and is only adjustable if you have a scanner. A timing light does not work on them.
These engines can be "timed" in the way you are used too.
The distibutor housing holds the cam sensor, The PCM calculates the timing by measuring the crank signal and the cam signal.
What you are seting by turning the distibutor housing is the correlation between the 2 sensors. On the V-6 model, the housing holddown bracket is fixed to the housing so if you return the rotor to the proper position when reinstalling the housing, the engine should be at the correct cam sensor position setting.they did not fix the holddown bracket to the V-8 models, it would have saved a lot of headaches.
To set the correlation between the 2, you will need a scan tool that can read camshaft position offset. With the engine RPM over 1200 adjust the offset too 0 degrees.
The ignition timing cannot be adjusted. The distributor may need adjusting to prevent crossfire. To insure proper alignment of the distributor, perform the following:
With the ignition OFF, install a scan tool to the DLC.
Start the engine and bring to normal operating temperature. IMPORTANT: Cam ****** Offset reading will not be accurate below 1000 RPM.
Increase engine speed to 1000 RPM.
Monitor the Cam ****** Offset.
If the Cam ****** indicates a value of 0°+/-2°, the distributor is properly adjusted.
If the Cam ****** does not indicate 0°+/-2°, the distributor must be adjusted.
With the engine OFF, slightly loosen the distributor hold down bolt. IMPORTANT: Cam ****** Offset reading will not be accurate below 1000 RPM.
Start the engine and raise engine speed to 1000 RPM.
Using a scan tool monitor Cam ****** Offset.
Rotate the distributor as follows:
4.1. To compensate for a negative reading, rotate the distributor in the counterclockwise direction.
4.2. To compensate for a positive reading, rotate the distributor in the clockwise direction.
Repeat step 4 until 0°+/-2°, is obtained.
Turn the ignition OFF.
Tighten the distributor hold-down bolt to 3 Nm (25 lb. ft.).
Start the engine, raise engine speed to 1000 RPM and recheck Camshaft ****** Offset.
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May 09, 2010 |
1998 GMC Sierra