Okay first post on this forum and hope it’s the right place. Have an 02 blazer just finished replacing all the sensors new dist cap and rotor and full tube up. New fuel pump, filter, and new upgraded spider. Recently replaced all gaskets from heads up. Its miss fire was happening before all of the new parts and gaskets. The misfire is bad and my light flashes at idle. It’s also throwing the P0101 code as well but I clean the MAF sensor. The only sensors I didn’t replace include the MAF, MAP, TPS, IAT. I’ve heard about the crank sensor relearn but it was doing it prior to the new one. Not sure what could be causing this. Compression was good on all cylinders at 135 and above. Still scratching my head as to what’s causing this

 

Aha, the parts cannon didn't work!!

1. Always start with lowest numbered code, since the early ones can cause the later ones to appear. This means fix the P0101 before anything else is done - They don't get any lower! We can definitely test it using the factory diagnostic charts. But you need to be committed to doing this right and following instructions. Otherwise I will leave it to someone else to help you. Please answer the following.

2. Can you feel a severe misfire, or is it just a flashing light and a P030x code? Is it a steady misfire?

If you replace or even disturb a crankshaft sensor, the sensor waveform stored in the PCM used for misfire detection is suspect. The detection is very sensitive and the PCM calls anything out of ordinary a misfire. Really doubt you could get a crank sensor relearn to initiate when there is a misfire, and you wouldn't want to record a misfire as normal (even if you could). I really believe the PCM expects to see some degree of increase in rotational velocity for each cylinder, and if the increase isn't there it refuses to initiate the test to record the waveform. However, know that an inappropriate crank sensor waveform WILL NOT cause a felt misfire - it will only report a misfire.

3. Do you have a capable scanner that will at least read cam sensor retard? Please advise brand and type.

 

You can definitely feel the misfire at idle as the whole blazer rocks like it has a dead miss. But once you take off it’s like it disappears. Can visibly see the miss while looking at the engine also. Well what I purchased it once of the crank sensor wires was cut and it wouldn’t start. After I fixed that it started. I just have the basic scanner that shows the basic stuff. I probably need to invest in a better one.

 

Ok first lets see how far we can get with what you have. First clear all codes and make sure p0101 sets again. Report please all codes that are set again after clearing.

If you just repaired a wire and didnt remove the crank sensor, then you didnt change anything. Is this the case?

 

If you want to go ahead and get a proper scanner coming, I have 2 choices for you. But you can wait and see how what you have works out, if you want. Dont know how much of a hurry you are in to fix it.

1. Car Diagnostic Pro app on Android - with BAFX bluetooth OBD2 adapter from Amazon. About $30 total. Good set of GM enhanced Powertrain PIDs for live data including cam sensor retard. Reads/clears codes for different modules like powertrain, abs, sir, hvac, etc. I have it.

2. Vident I-link 400 (GM firmware option). This is a handheld wired scanner. Does bidirectional functions like crank sensor relearn and also pids/functions for powertrain, abs, sir, hvac, tccm, etc modules. About $150. Does a lot. I have one. Various sources including Amazon.

 

This thing has set for many years. When I got it I tried to start it but I didn’t know one of the wires to the crank sensor was cut. So it had no spark. Fixed that issue but then also I replaced the crank sensor. I just done a compression test and hopefully I don’t have to pull the head again…. Here are the results with all the plugs pulled and throttle wide open.

6 - 175 5 - 1844 - 145 3 - 150

2- 182 1 - 180

 

It’s been throwing a code p0303 for cylinder 3 but then I’ll clear it and will throw a p0300 it’s only noticeable at idle so I’m still scratching my head…

 

No P0101 anymore? Please report fuel trims at idle and at 2000 rpm (all four fuel trims)

 

It still throws the p101 but only when driving. Okay when i get off work I’ll check those.

 

Does the compression check out good?