I have a '99 4.3L V6 Blazer that started having issues a year ago...long story short replaced spider, FPR, and Fuel pump...then had major issues the crankshaft bearing was going out...parked blazer with intention to replace motor ..my husband had a 99 Silverado 1500 V6 that was rear ended by someone and totaled...so we took the engine and transmission from Silverado and replaced motor in blazer...since replacing it was running ok sometimes would have to plug/unplug MAF sensor wires when it would run rough but after that it would run fine...until today...we replaced the intake and MAF sensor from Silverado with one from parts blazer that was same as mine and it ran great...but since swapping motor when switching from P, the other gears except form R, won't indicate in anyway that was selected...my right signal indicator stays illuminated on dash however signals theirself are functioning just fine...it evens blinks fast as if it was out but works normally...this morning on way to school, it drove perfectly fine halfway there until I got to stop sign and it just suddenly died...put in N cranked back up, sputtered but died again...so put in N, cranked it sputtered and drove on to drop son at school...it drove fine for me to drop him off and start return home...then it started sputtering and backfiring, and died...so did the N, crank, and gas routine again...it would sputter and slow and backfire and die...pulled off road and it backfired and died ...called my husband...he told me to start it again then unplug sensor wires and back then see if it would run normal...I cranked it, and it was as if throttle was stuck open...my foot wasn't even in the gas...and it wouldn't let off..when I did press the gas it would die ...when I unplugged sensor instead of fixing like it had done, it died...so like most other wives, I sat and waited on husband to come get me off side of the road..when he gets there I crank it up, and it was idling a bit high but nowhere near like had been...the pcv hose ( I may be calling it wrong name), was magically off he put back on and we started back home...once again ran normal half of the trip home, but once again it started doing the same thing...it drives normal and then out of blue it'll die, once it dies it'll do it more and more but it will start back up so far....it almost acts like it either builds up fuel and burns it off, or as if it gets starved for fuel and dies..when we got to road we live on he had to push blazer all way to house and it wouldn't start until coming up driveway...that time I shut it off...while we were standing there with hood up looking at each other completely lost and dumbfounded with it running, it just suddenly died...now the fuel pump that is in was fuel pump that was in Silverado since husband broke the new one for blazer before it was even installed...so anyone ever ran into issues such as these? Any and all information and help is received with the sincerest appreciation...and also, I'm not in anyway a mechanically inclined person...only info I know is what I've read, I have no sense to applying that knowledge and honest can't tell you much about any engine so I have no hands on knowledge at all...in short I am honestly and engine dummy...lol

 

I've never replaced a motor but I have seen a fair number of posts where people who have had had problems with bad grounds. Hopefully someone else can give better advice.

 

Thanks for your assistance !

 

I would start by borrowing a fuel pressure gauge from the local parts store and watching the fuel pressure when the problem occurs.

 

It does it while in operation

 

Might get the hose on a fuel pressure gauge shut under the back of the hood so you can still see the pressure while driving. Depends on the gauge and the length of the hose. Fuel pressure gauges for these vehicles simply screw onto a Schrader Valve fitting on the top rear of the engine at the side of the distributor.

 

You said "when we got to road we live on he had to push blazer all way to house and it wouldn't start until coming up driveway". Nevertheless you might get the hose on a fuel pressure gauge shut under the back of the hood so you can still see the pressure while driving. Depends on the gauge and the length of the hose.