Ok so i have searched and searched the p0300 code and have not seen any issues like the one i have.

So to start it off i rebuilt my blazer just after winter. Now it ran fine until the rear main went out. So i put new bearing crank seals the works into this thing.

Now I have a problem it lacks power. Not just a little power. Alot of power. It is missing and popping. So we put it on a computer scanner it the codes came up p0300 and p0340. So i got a new distributor and fired it up it wasnt missing or popping. as soon as i put it in reverse to do a test run it happend again started missing and popping. So the dist wasnt my issue. Cleaned the maf out. nothing. got a new one and nothing. Also im not sure but when we had it on the scanner the timing at idle was 24 degrees advanced? not 100% on that it was awhile back. It cant be a timing issue cause it ran fine when we put new dist in right? Im currently unemployed right now so cant take it in to have to fixed i cant spend any more big bucks on it eather so if there is any tests i can run please feal free ill try anything atm. also there is 2 marks on my harmonic balancer what one should we use?

 

Let's be clear about what happened and when.
You changed the dist. You started it. Idled and revved fine, then you put it in reverse and it went to crap. so now it DOESNT idle and rev fine in park?

OR it doesnt run well under load?

Are you still getting P0340? That's the issue. If so I suspect wiring. Or something else.
The point is that 340 is typically related to some fault in the CPS. common sense sez 340 causes 300. not something causes both. USUALLY.

https://blazerforum.com/forum/diagno...plained-38653/
However.. I think there's a clue here:
How does the PCM know the Cam pos sensor is not right? It has to compare it against something.

Suppose the Crankshaft position sensor is just a little flaky? did you disturb it when you did the crank work?
OBD-II Trouble Code: P0340 Camshaft Position Sensor Circuit Malfunction

Of course it just may be that the Cam and crank pulses are so far out of sync that the PCM is 'confused'

How does your tach act during the 'misfires'?

Read both those links.
24 deg seems just a tad advanced at idle IIRC.

 

You changed the dist. You started it. Idled and revved fine, then you put it in reverse and it went to crap. so now it DOESNT idle and rev fine in park?

It misses pops at idle and when i put it in gear it wants to stall. When i accelerate it is super sluggish. Also is hard to start takes a while to get it to start.

It doesnt have a tach but the scan tool we had will tell us ill write it down and let u know when i get back.

Still getting 300 code im going to head over to the shop here in about an hour and check it out with my uncle do some wire checking.

 

Ok i Checked the wiring and there isn't any cracks in the wires spent 2 days checking them even checked all the way back to the transmission The only thing i havent changed is the cap. So going to grab a new cap monday and see if it works. The cap on there looks good it was just changed before the rebuild.