95 Maxima won't start screws up POS count

I have a 95 Maxima that will not start. Cranks over and occasionally will back fire in cylinder head. My mechanic tells me that the POS count should be 180 but it is all over the place when cranking over. His Tech line told him he had a bad ground between the engine and tranny so he pulled back tranny and cleaned between engine and tranny with no change resulting. He has only one code for evap purge or something that seems to be unrelated.

Car is a standard and if we roll it then it jumps starts perfect. Problem is I am going to need to engage the starter to drive it around. As soon as you engage starter it screws up the crank sensor.

I saw on a website corrosion of cooling sensor can cause no start but would that effect the crank sensor? Please help 3 weeks no car? Thanks

The only thing that hlps in this matter is another mech. Must have been Apr1 - when loosing gnd between tranny and engine... bad joke.

Read/check issues mentioned on link below and then start cleanin all connectors.

If your car is actually backfireing the timing may be to far advanced or, as you said, something may be wrong with the crank sensor. There are two on your car, ref ( under crank pully) and POS, along the backside of the bell housing. If i recall the POS sensor mesures the speed of your engine, and the REF determines TDC ( Top dead center ) and work with the cam senor to determine fuel and spark pulse width etc. Inotice when i changed my starter it crank quicker and fired sudsiquently faster. I think there mat be a threshold level between how fast the motor turns , via the POS sensor, and if and when fuel/spark are activated. Just something to consider. As for grounding. I cleaned the heck out of my Neg. battery cable where it connects under the air box, and to the Engine. It was very corroded. How much value that added i cannot say for sure, but i feel it helped. I suspect a bad ground may also cause the volatges that the ECU receives to be lower then normal and hence may also contribute to starting problems as the ECU may not be able to turn these low, or erratic voltage signals into usable information ( hence hard starting). Defniely clean the cable grounds now that you know the tranny ground is good.