Hi folks,

I recently did some work on my Blazer which required me to pull the distributor.

When I put the distributor back in, it fired up but threw code P1395. Checking, I had it one tooth off, about 28 to 30 degrees advanced.

When I reinstalled it with the teeth aligned as they were before dis assembly, the code went away but the motor picked up the P0300 code.

I advanced it one tooth again. Perfect idle, smooth acceleration, no misfires whatever. It ran like a new 4.3, but the code came back.

The motor wants to run best with advanced initial timing.

I'm wondering now if perhaps the distributor gear was worn. It didn't look it, but neither did I clean it to really check.

Do you folks have any thoughts on this? Should I just have a CASE done and call it good? Inspect the distributor gear better?

Thoughts are welcome.

Thank you,

Josh

 

I believe it needs a cam relearn procedure.

kinda like this https://blazerforum.com/forum/2nd-ge...e-train-79000/

 

Pull the distributor and inspect the gear for wear. Very common for the gear to wear on these engines if it has high mileage. If it is worn you can get a skip white all aluminum distributor for $40.
The P1345 code means you're out a tooth. The cam retard may need to be adjusted to correct the P0300 code. If the distributor is not correctly aligned it will cause crossfire within the distributor cap. You will need a shop to adjust the cam retard. A cheap scan tool is not able to read that PID.

 

Car Gauge Pro for Android and BAFX bluetooth OBD2 (from Amazon) will read the cam retard. About $35 total for app and bluetooth device.

 

There is no such thing. (I also originally mixed up cam retard with CASE relearn)

 

Advancing the position of the rotor in the distributor does nothing to change ignition timing. That is determined solely by the crank sensor and the PCM - timing is not adjustable.

Here's something to think about... why not test the misfire detection system and see if it works correctly. If misfire detection is working correctly, then a CASE relearn will not accompish anything.

 

Where can I find this Skip White distributor? I'd consider an aluminum distributor worth it even without the actual need for it.

Thanks!

Josh

 

Burned,

It was crossfiring before. Now it's not. I should have mentioned that it appeared to have been crossfiring when I tuned it up last; it slipped my mind until you reminded me.

When I talk initial timing I only mean timing with the advance/retard signal disabled... though this may be applicable only to the previous generation CPI.

Les,

When I talk initial timing I only mean timing with the advance/retard signal disabled... though this may be applicable only to the previous generation CPI.

The misfire detection system, so far as the basic scanner can read, tests "OK".

_______

Guys,

Something else I forgot to mention was that it appear the distributor had been out before. The gasket was missing -- gone, no sign that it had worn out.

My hypothesis, right now, is this:

Sometime in the truck's past, before I owned it, the distributor was pulled. The gasket was lost and the distributor was reinstalled one tooth off and a CASE relearn was done instead of a double-check of the distributor.

It's always lacked the power a 4.3 should have. I attributed this to faster gears as I've always owned 3.73s. However, this looks to not be the case.

When I checked distributor alignment, it does align with #1 TDC now. Apparently it did not, previously, though I didn't check that alignment.

Thoughts?

Regards,

Josh

P.S. This is one reason I didn't become a technician out of school. I've never liked fixing others' messups. This appears to be one. J.S.

 

Sorry, that's not what I am talking about.

I'm talking about inducing a miss on a specific cylinder and seeing if the PCM can detect it definitively. If it can't detect a real miss, then you have a problem in your misfire detection system that is most likely setting a false P0300 code.

If it can reliably detect the induced miss, then the P0300 general misfire code is most likely from a real misfire.

I think this is one of the easiest and most basic functional checks that is almost always overlooked when diagnosing misfire codes. It eliminates a lot of guess work and can send you in a definite direction.

p.s. Distributor gets dropped in with engine on TDC#1 and the rotor pointing towards the stamped 6 in the distributor housing (not pointing to #1 terminal). And yes, Burned is correct that the cam retard being off could cause a real miss and a P0300.

 

Hello,

Yes, it detects induced misses.

Regards,

Josh