My Blazer has not thrown a check engine light yet, but my Blue Driver scan tool reveals that there is a pending P0300 code for random misfire. While idling you can feel it occasionally skip a beat.
So I pulled off the distributor cap to look for any wear and tear. Before I took the rotor off to look underneath, I just wanted to line up the timing marks to make sure everything is as it should be.
The crank pulley is at the TDC mark, but the distributor is not.

In these photos, the crank pulley is lined up.





With thte crank pulley set, this is where the rotor was pointing. Inbetween the 6 and 8 marks. It's not lined up with the 6 like I expected.


Here's underneath the rotor. I marked an arrow showing the direction the rotor was pointing. Those 2 holes is where the rotor mounts and screws down.
I also noticed two other holes that seem to line up with teh 6 mark.



I tried mounting the rotor with those two holes and now it seems to line up wiht the 6, but there's no where to screw it down.


So that's the mystery. Is the timing off or is this by design?

 

It seems your timing marks are lined up - check with this attachment pp 15-16. But rotor is far off - should point to 6. I would think it would set a P01325 this far off and would not run. Very strange. I would concentrate on figuring this out. The ring on your balancer may have slipped.

Just curious why the arrow drawn underneath the rotor. It is pointing opposite distributor rotation.

 

I think I'm missing something.

Yeah, my crank pulley is lined up with the timing marks exactly like the illustration on page 15. Before turning the crank, I verified where the timing marks are on the block with an image search. Found that same illustration and I see it comes from this documentation. I didn't remove the #1 spark plug though. Is that crucial?

 

I tried to show how the rotor would have been mounted. I may have not draw the arrow straight.

 

What would happen if I put the rotor on backwards? Would the engine just not run at all, or would the ECM try to compensate and adjust the timing on everything?

This mystery actaully does seem to explain what I'm looking at under the cap in this thread. https://blazerforum.com/forum/2nd-ge...64/#post740305

 

You missed what I had added to post #2 after you first looked at it. I was still writing. I think your balancer ring must have slipped. Has zero effect on timing or cam sensor retard but makes very difficult to get distributor back in right if you ever take it out, unless you drop it back in with rotor pointing to exactly same spot and without turning the engine.

Removing #1 is not important if engine runs.

 

Oops sorry. I have my email open so I'm just getting live notifications as I'm doing my research here.

Maybe #1 isn't at TDC afterall. I guess I could turn the crank until the rotor lines up with the 6. Then it would be at TDC I think.

 

So I entered 2002 Blazer into Blue Driver Compatibility on their web site and came up with only this for live data. Sorry, but Blue Driver doesn't seem to do much for live data on our Blazers.

You may be able to use the Blue Driver dongle and an inexpensive app to do the cam sensor retard live data. But need to know if you are on Android or iPhone and if dongle is Bluetooth or Wifi connection - in order to tell you what software will work (or work best). The cam sensor retard is the critical thing to check before you replace anything. As far as slop in the distributor gear - how many distributor degrees of slop before rotor starts lifting, and how many degrees total (including the lifting from the helical cut gears).

 

@LesMyer Android 11, Bluetooth.

I was using this OBDII adapter before the BlueDriver. So I have this and the BlueDriver at my disposal with whatever diag app will get cam sensor retard.

 

so hold up a ruler next to the rotor and measure the slop.

(movement of rotor/distance from center to edge of rotor terminal) * tan (-1) = DEGREES OF DISTRIBUTOR GEAR SLOP

There are 13 teeth on distributor gear so 360/13=27.7 distributor degrees between teeth.