Question about 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.
Thank you for using fixya and good luck.
Posted on May 09, 2010
If service engine light is not on, don't change timing it is ok
Posted on May 10, 2010
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Posted on Jan 02, 2017
First of all...does your truck have the retained accessory power (RAP)? If it does, the radio would always stay on with the key off until you open the drivers door. If it does have RAP and the door pin on the drivers door has went bad, then the truck doesn't know that you opened the door and continues to allow accessory power (although it would still cut off after about 20 minutes). If the interior lights come on when you open the door, then the pin is ok. If the lights come on, it could be the RAP relay. If it has gone bad, it is possible it is stuck supplying power and needs replacing. The relay should be labeled in the fuse panel, and there should be other relays in the panel with the same part number. You can swap a relay for the RAP relay and see if it fixes the problem...if it does fix it swap the relays back and replace the RAP relay. If the truck doesn't have RAP then it is possible the problem is in the radio..if you have a friend with a GM car or truck close to the same year you could swap radios and see if that fixes your problem...should be pretty simple. pull the cover off the dash, it just clips on, take out a couple screws that hold in the radio, unplug it and plug in the other radio. sorry so long winded...hope this helps you somewhat.
Posted on Mar 13, 2009
The timing is not adjustable and it is computer controlled, but the distributor must still be clocked in properly and static timed, and here is how it is done.
There is a mark or notch on the distributor housing that the rotor should be pointing to when the engine is on top dead center. This static timing is all that matters and the computer will be able to control the timing as long as the ignition rotor is in that position when the engine is at top dead center.
1. Place the engine at top dead center.
2. Look under the distributor cap and find where the number one terminal runs under the distributor cap, and where that position on the distributor cap corresponds with the distributor housing, and it should match up to a mark or a notch on the distributor housing.
3. With the engine on top dead center the ignition rotor should be pointing to the mark or notch that is on the distributor housing, if it is not then loosen up the distributor and turn the distributor until the ignition rotor is pointing to the mark or notch on the distributor housing, the engine should now be static timed.
Posted on Jun 12, 2010
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