I have a 01 zr2 blazer has a misfire p0300 won't let itself shift to overdrive when light flashes got cmp retard set to 0 still wouldn't lock up torque converter you can't feel the misfire but the computer detects it if I unplug the cam sensor from the back of the distributor check engine light stops flashing and the Blazer will go into overdrive on the highway like it's supposed to any help would be great I believe my crank sensor is being hit by the reluctor wheel because if I floor it the tack will go crazy at about 3,000 RPMs just don't know if replacing it will fix the overdrive misfire issue sometimes it also cuts out for half a second when driving at 45 mph between 2000 and 2300 rpm but catches itself and drives fine not totally sure where to post this I've read the forums a lot just made an account

 

It only takes a few minutes to pull your crank sensor out and look at it. If you replace it, though, remember that you need to do a re-learn on it.

 

I thought if I remove it I'll have to do the relearn procedure? I'm almost positive it gets struck on hard acceleration when the tach jumps hard. My major question is can the crank sensor give me false misfire data when cmp is plugged in making the torque converter not want to lock at highway speed? My temporary fix was to set cam position retard to zero this was done with the small block Chevy hold down for the distributor and just unplug the CMP sensor so the computer can't detect misfires allowing the torque converter to lock up at highway speed so I'm not in high RPM sucking gas thank you for the help

 

Yes, technically you should re-learn it any time you disturb it, but you'd probably be fine. A bad sensor can definitely cause that code, and I believe that code can stop it from shifting into OD. What would be weird is if it just suddenly starting hitting the reluctor wheel. That would indicate some other problem.

 

Honestly I've been suspecting it hitting the reluctor wheel for quite some time probably about a year and a half but I've had 10 million other problems did the head gasket intake manifold gaskets vacuum lines spark plugs wires distributor cap rotor but through everything the misfire and not shifting to overdrive was always a problem no matter what I would change the only code I would ever get was the random misfire which it wasn't until I recently replaced the distributor with a brand new unit all aluminum and set the cam retard to zero drove it and it didn't seem too much better tried unplugging the cam position sensor and it seems to drive fine now with overdrive engaging as it should it will still occasionally cut out while driving for half a second would that also be due to the crank sensor?

 

Hard to say. But I would definitely check it and replace it if necessary. If you can get your hands on a capable scanner, the re-learn only takes a few minutes.

 

Would u happen to know the cheapest capable scanner I've been using torque pro don't think it does it? Am I hurting anything running with the cam sensor unhooked will it use more gas or anything strange or just not detect misfires? And lastly when the sensor does get hit what does that do if anything to the injector or spark going to the cylinders will it cut the spark and injector to whatever cylinder it thinks it should be getting those things sorry if that's confusing

 

To be honest, I don't really know the answers to those questions. Hopefully the smart folks will be along soon, lol.

The Tech2 clones you can get on Amazon or eBay are pretty decent from what I've heard, but not super cheap. I borrowed a Snap-on scanner to do mine.

 

Well thank u for the reply it seems to run fine without that cam plug hooked up just don't know if it affects anything else in a poor way like gas mileage. to me it seems like the crank sensor is getting hit or got shifted from being hit and gives a false misfire when it talks to the cam sensor when it's plugged in but Im not sure a false misfire is even a thing that can happen or if I'm confusing myself lol I haven't bought a new sensor yet or tried to shim it because I don't want to spend more money on it to have it still not really change anything. Is that what the relearn is for to correct false misfire readings?

 

It basically "times" the sensor to the crank but, yes, random misfires are a symptom of it being out of whack. So, when it's working correctly, you shouldn't have that problem.