LS1W

iTrader: (89)

hi - heres what i have going on - i just built and installed a new 5.3 for my 2000 GMC Sierra truck. - the old motor was obviously a steel block 5.3 with the knock sensors under the valley pan and the cam pick up sensor in the back of the block by the oil pressure switch hole ( typical ls1 set up )

-i used a late model aluminum ssr block for the build along with the later model cam gear/front cover pickup assembly - ( typical ls2 set up )
i still used a 24 tooth reluctor wheel

-i purchased the adapter harnesses from katech for the knock sensors and the cam pickup sensor / everything plugged in just fine - but truck will not run at all / it fires ( barely ) and wants to spit and cough through the air cleaner like the timing is way off or the cam was installed wrong

( i have had this engine running on my stand with a DIFFERENT MEFI-IV stand alone harness using the katech adapters for the knock sensor and cam sensor and it runs just fine ! fired right up, exc oil pressure, no issues at all

i put it in the truck and hooked the factory harness back up and now it does not want to run / has anyone used these adapter harness before ? does the computer need to be tuned using this ?

i am completely confused - if i hadnt fired this up myself and heard it run i would be pulling off the cam cover at this point -

any ideas ??? and no, as much as it wont run, it is NOT throwing codes, i have checked continuity in the adapter harnesses and i have good connections, i also have proper voltage from the trucks harness with key on to the cam pickup sensor plug end in the factory harness

thanks - shane