The tach runs off of the CMP signal, not the CKP signal.

The EGR valve can be cleaned quite easily. If there aren't any codes, a good cleaning an reinstall with the upgraded, screened gasket should be all that is necessary to eliminate that from the possible causes.

A compression check will tell you if you have any imbalance in the motor.

When you replaced the distributor, did you set CMP retard to zero and then run a CASE relearn? Both are required for the PCM to know precisely where the rotor is in relation to the crankshaft. Both of these procedures require a full feature scan tool to complete.

The P0300 code listing in the OBD2 section has a link to a thread that has a rather exhaustive listing of potential causes for a multiple misfire.

 

I will check that thread out, thank you.

Also, I have not done anything as far as setting the cmp retard, I do not have access to that tool and don't have the money ti keep taking it in to a shop to try things. My biggest worry was the timing cover as I have read quite a few reviews saying the autozone pioneer timing covers lead to this problem. I'm about at wits end with this because in getting to things I cannot do without the computer at the shop. Are there any scanners that can be purchased at Walmart/autozone etc? That are a semireasonable price? Then I can atleast have it to be used on other vehicles

I will plan on trying a compression test later this week

 

Unless the timing cover was machined improperly it seems unlikely that the replacement timing cover would cause such terrible misfiring issues. Did you line up your crank and cam properly when you did the timing chain? I replaced my timing cover, timing chain, etc when I swapped in a new motor, but I reused my original distributor, reluctor ring, and crankshaft position sensor. Apparently I should have done a relearn but everything's worked perfectly the past few months and I think I'll save my money. I would look for ignition problems (improperly installed distributor, bad wires, unplugged distributor/ crank sensors, bad cap or rotor) prior to taking the car to the dealer for the relearn. I would also do a fuel pressure test and leak down test to rule out your injector lines and fuel pump. I would do the compression check last because it's the hardest test to accomplish.

 

Help please? New motor 4.3 Cranks but no start/spark?? - S-10 Forum

That is the only thread I can find right now about the timing cover, however I know I have at least one other on my computer.

It seems as though the sensor is up high enough vertically (1/32 of an inch or so from sensor to reluctor ring), just unsure if it needs to be moved laterally.

Also, is there a way to test this sensor specifically?

Distributor has been installed by me and a mechanic multiple times, and had no bearing on motor running better/worse. The distributor is new, however cap and rotor are the ones on there when I bought it. I cleaned them both up, and they do not look very old at all.

Tested the fuel pressure, and seems right on par with where it needs to be. The mechanic pulled the injectors out and put pressure in the system with the pump, then sprayed the injectors to check the spray pattern, and look for leaks, all of that checked out as well.

 

THIS THREAD might be what you're thinking of. I'll post back up if I find the CKP test procedure. I'm sure I've posted it in the past, but I don't have a lot of time to search.

 

Yes sir, that is the one. I will try and do some research to find it, and start reading up on the thread in OBDII section and post back. thanks guys

Also, I should add. This misfire seems to not be detected while under a decent load. It is extrememly prominent while I am decelerating and decently prominent when under a light load (like leaving a stop light/stop sign)

Also, how much timing is commanded at idle/light load? I was seeing 30s-40s as far as how many degrees the computer was asking for. I can try to get a scan if that would help, although I dont know how much data it will pull. (I am using the Torque app for Android with a bluetooth OBDII since my cars tuning software DHP PowrTunr doesnt seem to support the 4.3)

Ok, Im doing a lot of research here at work, and getting slightly confused. This is saying that the CKP is used to help the PCM decide whether or not there is a misfire by a difference in the pulse speed between two seperate intervals. If this is the case, then this CKP (and timing cover) have nothing to do with my misfire? I can tell that there is quite obvioiusly a misfire, and the PCM is not confused. The thing barely idles when its cold and then dies as it warms up.

Also, I have access to an old AutoTap scantool, is anyone aware of this being able to perform the relearns that I need it to?

 

Got GM timing cover in. Going out tonight to tty and measure some differences. I'd it possible ti drop oil pan if the front axle is pulled out?

 

Bump for a late night crew

 

Two videos. They are one right after another but my phone separated them midway through. This is with me not giving it any gas at all, just the blazer keeping itself going.


The pioneer timing cover does seem to be holding the sensor a little bit further away laterally that the GM cover would, however I cant be sure because the Pioneer one is on the bloock and hard to get a measurement on. The distance away fromt he sensor to the reluctor ring should be, by my best measuring abilities, .030 inches, I would think that is enough to get a clear signal. Although, again, I am not exactly sure if this sensor is necessary to be working until I get it running right, I never got an answer to that. Does the engine need to CKP to idle correctly? Or is this just used to help identify when and where the misfires are occuring? Also, would this sensor being bad trigger a SES light?

 

The radial distance between the reluctor ring & the sensor is what matters. The axial position of the sensor doesn't matter to a point... The sensor should be close to center of the reluctor ring.

A good CKP signal is required for proper spark & injector timing. If the signal was inconsistent due to too much of a gap, it could certainly cause a misfire.