2002 Chevrolet Blazer 4.3L P0300

Vehicle came from another shop, has new distributor, AC delco plugs and wires, New spider injection, Bank 2 Sensor 1 oxygen sensor is New. The truck develops a slight, random miss at idle, can hardly feel it, when looking at misfire data, it has misfires on cyclinders 1-4, and ive never seen or 5 or 6 misfire, MAF at idle reads about : 4.7. Map Sensor Reads 10 to 11 at an idle. 02 sensors seem to be switching well, however when looking at fuel trim, after idling for periods of time short term fuel trim will be -7 and continiously take fuel away. I can add propane and misfires completely go away, Im stumped why it would constantly be taking fuel away, when fuel is added it runs correctly.

Compression test results
1: 160 2: 155
3: 155 4: 165
5: 155 6: 155

Next thing im going to do is scope the cam and crank sensors, and see whats going on at an idle.

Am i missing something? anybody have any ideas or suggestions? Thanks in advance.....

Vehicle only has 126k on the truck.

anyone have a pic of good can crank 2002 4.3

any thoughts ...... my head hurts. thanks ED

Was the pressure regulator in the intake manifold checked to see if it is leaking? If its not leaking i would be leaning towards the 02 or a bad new injector.

regulator is new, not leaking and hold fuel pressure, Thanks ed

I have run into this. You should be able to do a cam crank relearn thur the scan tool to take care of this. It is often overlooked

i already did a relearn. but thanks ....