So I have a project that I have been basically restoring. Long story short, it wasn't running when I bought it and I have torn the engine down to ensure there weren't any issues.

I get a p0300 code displayed. I plugged in my scan tool and found that the misfires are coming from cyl 6 & 2. It can't really feel the misfire due to an issue with the exhaust that I'll explain below. I went ahead and raised the rpms to around 1,000-1,200 and found that cyl 6 & 2 no longer misfire at all but cyl 1 shows to be misfiring ticking up to 150 misfires before each reset while 6 & 2 only get to about 30-50 misfires per reset at idle.

I have replaced just quite a bit because either it wasn't in the bin of parts I was given or I didn't trust it. So, bottom end was good and I didn't mess with it. I had the head professionally torn down, cleaned, tested, and reassembled. I didn't get the manifolds with the vehicle so I purchased headers. The headers exit are wider than stock so I cut the y-pipe and I am going to have it welded to fit once I can drive the vehicle. Only the upstream O2 sensors are installed at this time. The ignition module, coil, distributor cap, spark plugs, and wires are new. The fuel injection spider and injectors are new from GM. The fuel pressure is good and doesn't leak down. I've also replaced the throttle position sensor. Compression was good when I checked it before I put the headers on. The scan tool is showing that I am running lean and that I am advanced at 16 degrees steady. I do not remember what the voltages were for the O2 sensors however. I am wondering if maybe the cam sensor is starting to malfunction but not showing yet. If that is the case, I'll probably just replace the hold distributor since it came with the vehicle (I thought about doing it before but against my better judgement I didn't). If anyone has the program to inspect data logs from a snapon scan tool, I would be willing to record and send them to you. I'm sure I am forgetting some information, so feel free to ask me questions and I will reply as fast as possible. Thank you.

 

Hey, another Florida Blazer!
my rig was a similar situation what with it being torn to the gills (not to the heads but frontend and topside) and left to sit for a few years Check distributor lash by hand, and if anything put a new gear on it, its just a rollpin and it comes right off, cheaper then replacing the whole distributor and unless its super old the bushings should be in good shape.

Assuming the top end is sealed up, no vacuum leaks, intake manifold (lower and upper) air leaks and the intake tubing is tight, Make sure that the distributor Cam Retard value is with +-2 degrees of 0, the distributor is aligned correctly and not warped, ignition components are good, connections clean, plug wires fully seated and routed correctly, not loosing spark due to bad wires, etc.
If all that checks out, then you can start checking more on sensors before moving on to a different part of the sequence of suck squeeze bang blow.

 

I double checked all of my vacuum lines and haven't found anything visually. I tried using brake cleaner to spray across the lines and nothing happened so those are good. I will double check the cam retard value. I checked the lash on the distributor when I originally installed it but I had installed it a couple teeth out and had a GM tech to help get the timing correct so it wouldn't surprise me if I had messed something up there. I was thinking about replacing the whole distributor as a precaution. That way the distributor and cam sensor are all new. I replaced the cap with an autozone one before I got the vehicle running so there is a possibility there. I'm going to be replacing the fuel filter tomorrow. Not because I expect that it is bad but I don't know the last time it was replaced and the fuel that was in the tank smelled horrid. I drained the tank and put good fuel in it so I know the fuel going into the engine is good. I'll let you know what I find on the all of the other values. Thanks for the help so far.

 

These trucks are picky with their ignition parts, mine outright refused to run until i put a GM Cap/Rotor on it. with the other issues present i would highly doubt this is an issue but once the cam retard is set and the timing advance is figured out and it keeps having problems look into it (im not sure what a normal range is, the computer should be changing it over time as it warms up and under load)

 

I got to look at it today after doing to some repairs to fix some fluid seepage. I noticed that the guy who messed with it for me a little bit ago over-tightened the screw that held the cap on in the front near 2 & 6. I put an oversize screw in it and it is holding tight but the misfire is just as bad. I checked the data and found that the system is advancing the spark but the cam retard is at -9 and holding still. It doesn't change no matter what I do. The knock retard is showing 0 and is holding steady there. I was looking into doing just the sensor for it but I think that I am going to just get a whole new distributor for the simple fact that I don't know the history of the part and I don't want it to just randomly go out on me later on. I'll have to order it so I'll let you know any updates after I get it in there. If that solves my problems, then I'm off to get an exhaust made for it.

 

fix that exhaust leak first, then get back to this.

after thats done, if the distributor is damaged then replace it, as far as the cam sensor retard values you change that by rotating the distributor body with the holddown clamp screw very slightly loosened and setting it to 0 or within +-2 degrees.

 

To fix the exhaust I would have to get it to a running and driving condition as I need to take it to an exhaust shop. I will getting a new exhaust here soon. I may have to tow it to the shop if need be. The distributor is a fixed position one. So I can't twist it without actually removing it. If it were out of time, wouldn't I have misfires on more than those two cylinders? I've always had a misfires randomly on all cylinders when the distributor was out of wack. This vehicle was done a lot of things that it shouldn't though so maybe that's just how the vehicle is.

 

My mechanic drilled out the piece on the distributor enough to adjust it. Was at a +9 when then engine was swapped, then got it to a +2 after expansion.

 

I've got the new distributor and cam position sensor installed. I installed it using the same location as the original. I now do not have any misfires but I am showing P1345 CRK/CAM Correlation Incorrect. They vehicle runs much better and doesn't try to stall out when the pedal is rapidly pushed. I am however seeing that there is -35 degrees on the camshaft position sensor. I would say that I installed the distributor incorrectly but since I don't have any misfires what so ever. I would assume that it is correct and that it couldn't be off that much. I was thinking that maybe there was something that I needed to do but it doesn't look like there is any relearns that I can do. I am unsure of how I would go about checking the crankshaft position sensor. Any ideas?

 

Distributor gear is off 1 tooth.