Chasing down a nasty misfire and I pulled the cap for a visual check. Rotor has a nasty burn mark and there's white oxidation on the cap terminals. Both are AC Delco and were replaced 7 maybe 8 years ago. Rotor is a D465, cap is a D328A which is what rockauto recommended. Not happy at all with the looks of that rotor though.

Cap


Rotor

 

Replace both, they are cheap enough. However, I haven't used AC /Delco cap and rotor for a number of years due to the oxidation. I use aftermarket cap and rotor that has copper instead of aluminum. My cap and rotor now last much longer than before and I haven't been stranded due to oxidation. I don't have the stock distributor, either.

 

If you don't mind, what cap and rotor are you using? I know these engines can get real picky on some parts when it comes to electronics. It seems I got lucky with my MSD wires but only because they're 500 ohm/foot like the AC Delco. That's the only reason I didn't go brass since that's what I typically go for. I'm stuck mid-cross country move with 99% of my tools already waiting for me in Texas while I'm still here in Washington. I mean, I had to walk into the store I left for this move and buy T10 and T15 bits... and i sold tools and hardware there. I already have a cap and rotor on order but at some point I'm sure I'll need (hopefully after I'm in Texas) to replace the distributor. Over 220k on it and even the coil is the one it rolled off the assembly line with (still riveted) and tested good. It's a rust free beauty of a survivor and I'm waiting for the transmission to give up the ghost (already replaced the solenoids 5 years ago) before deciding if I'll rebuild the 4.3L or have a little fun by adding 2 cylinders and a full liter of displacement (it's active AWD with the Trailblazer trim level) for a little SS action.

 

at 90K I had some noise coming from my distributor and I saw the cap and rotor were messed up. I replaced them but the prob was the distributor.

 

I don't recall where I got the brass cap and rotor, but I know it was one of the national auto stores (NAPA, VatoZone, etc). Go on their websites and look. Not all of them carry the brass ones but you should be able to find them. If not, try Summit or Jegs, maybe RockAuto.

 

Turns out the rotor had a spark blow through (at a minimum) the center that caused all the headaches. I'll still be checking the timing when the OBDII scanner comes in but here's why you need to look beyond the surface condition!

 

Definitely a bad rotor.

You do realize that the ignition timing is not adjustable (is determined by crank sensor and PCM with inputs from other sensors)? What needs checked is cam sensor retard, which is the rotor position when the spark does come through. Needs to be zero +/- 2 degrees.

Good luck and best wishes. Let us know how the cam sensor retard is. I imagine that cam sensor retard being off could damage the rotor like that. We know it can damage the cap. Definitely worth checking.

 

Sorry, when I said timing, that's what I meant, the CMPRET value.

 

Well, not having any luck getting the software and OBDII to find a CMPRET value for me to view much less log. Using the BAFX for Android and Car Diagnostic Pro (even purchased the full version). What am I doing wrong here. Samsung Galaxy S10+ is connecting to the BAFX but I'm not getting a pid for the CMPRET, just some pretty basic fuel trim, rpm, maf, and base timing

 

Took a little bit to finally get the cam retard (and all the other pids) to register but anyway, it's reading a -5.0 +/-0.2. So is it new distributor time then? It'll be my first time changing one. Any brands to lean towards or stay away from?