99 grand Cherokee 4.0 engine swap timing trouble????

Asked by Aug 20, 2016 at 09:53 AM about the 1999 Jeep Grand Cherokee Laredo 4WD

Question type: Maintenance & Repair

Motor blew in my 99 grand Cherokee 4.0 I bought a
2000 GC with a recently rebuilt motor but the
transmission was bad but the motor ran really good
less than 30,000 on it anyway I swapped motors
and got everything hooked up but when I went to
start it it's acting like its firing at the wrong time
back firing out the intake and so forth I've checked
pretty much everything in getting spark at the plugs
the only thing is that after I tried to start it I noticed
that I forgot the crankshaft position sensor bolt so I
put it in then I realized it didn't have the spacer on it
could this cause this problem also the vehicle set
since January so I'm sure the gas is bad could bad
gas cause it not to start and backfire out the
intake?? It's my daughters jeep and she starts her
freshman year of college this week so she really
needs this car so any input would be a godsend so
please help!   Thanks everyone for your time on this
never ending post.

1 Answer


The spacer is there to make sure the air gap is correct from the sensor and trigger pawl, check the end of the sensor and make sure it was not damaged during cranking, also bad fuel will cause pop back, shelf life of today's fuel just sitting in a fuel tank is at best 60 days without any additives.

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