Ok first off I have a 96 Park Avenue 3.8 V6 with around 135K miles on it. It had started a few months back taking a while to start. It would turn over a while and then I'd stop and again and stop and usually the third time itd fire up. Well today when coming home it started making an odd clunking type sound and seemed like it was losing power. Then it began to act like it was firing on all cylinders or something and sounded like it was spark knocking and finally it just cut off in the road. I got it pulled over and tried again but to no avail, it will not start. It turns over but won't crank. I have heard it may be the crankshaft pos sensor, but I have no idea. It almost seemed like it had jumped time. I am a mostly novice when it comes to major repair work though. Please help, I am without a car/ride to work until I can figure this out. Thank you.

Make that wasn't firing on all cylinders* sorry

The car needs 3 things, properly timed, to run. Fuel, air/compression, and spark. Figure out what you dont have and we can go from there. Also, was the service engine soon light on? Have you scanned for codes? Sometimes you may get lucky and find the failure set a code, pointing to a place to start.

I'm pretty sure you have fuel and spark because it almost seemed like it was going to start back a couple times but I didn't continue to try. Also the car had been running excellent 10 mins prior (know that doesn't always mean anything, but still lol) and yes the light was on beforehand. I do not have a way to check codes right now but may soon when I take to a friends. Everyone I know is telling me the crankshaft or camshaft sensor is probably the issue especially since the car had been running perfectly and it is a common thing with this motor they say. It was doing great but after I had driven about 15-20 mins things got a little rough and then slowly deteriorated from there.

Cam sensor usually will not cause it to die. Crank sensors typically show themselves by not starting after being shut off, but typically just fail, killing the engine. When the crank sensor goes, you usually lose spark and injector pulse. Stumbling is more often fuel or ignition, but usually favors fuel. I would start checking the vitals before you start throwing parts at it. Is it throwing spark across all 3 coils? How much fuel pressure is at the rail? Are the injectors pulsing?

Sounds like the crank sensor to me.
If you want info on testing the crank sensor I could get you some info, you'd have to get a multimeter, and make a little LED test light, you'd want to test it when it is failing.

Check vitals like rjolly suggested, then if you determine it needs replacing, and you want to replace the part yourself, then here is a thread that will help.
https://www.gmforum.com/mechanical-1...sensor-279066/




A off topic tip for the future, if your Dad has never had the lower intake manifold gasket changed, I recommend planning to have the LIM Gasket replaced with the aluminum framed Fel-PRO LIL Gaskets.
The nylon LIM Gaskets are known to fail, and can lead to a hydra-locked motor, and possibly a destroyed motor.
https://www.gmforum.com/mechanical-1...ts-l36-297702/

If it'* cranking over and trying to start I would unplug the mass air flow sensor and see if it will start. I have seen the MAF cause what your discribing more than once.