1999 GMC Jimmy misfiring, replaced engine....PLEASE help.?

Question

This is a 1999 GMC Jimmy. The engine was just replaced and it's still not running on all 6 cylinders. Here are the details:

P300 random multiple misfire code, seems to smooth out above 1000 rpms, but at idle runs rough and kicks back, when scan tool is on the timiing vaires from 9-22 degrees at idle, everything electronic and fuel related has been replaced, seems to kick back when starting, just replaced motor because it kicked back violently enough to break the nose cone and 3 starters and shear the bolts off, now has a big starter in it so it cant do that, it even eventually crushed the bearings in the original motor. It starts right up but obviously isn't running on all 6 cylinders, tries to kick back but cant with the large starter. It seems like every possible solution has been tried, this truck is eating up so much money. ANY suggestions will be greatly appreciated. Thanks in advance.

Answer 1

bad distributor

Answer 2

Sounds like your initial timing is too far advanced.

Try setting it at 0 at idle.

Answer 3

Sounds like a huge fairy tale to me. Starter can't 'kick back" as the design of the starter disengages it if engine tries to turn backwards. How do you "crush the bearings"? There is no 'large starter" or"big starter" as you would have to completely alter the mounting of the starter and the bolt hole design. I say it's all in fun for some of the "mekaniks" on here to answer. Oh, and what is the "nose cone" that broke ?