99 bravada sputter & backfire

99 bravada with 148,000 miles on it. The guy i bought it from was a mechanic and says the motor and tranny have bout 90,000 on them. On to the problem. It has trouble starting and when it does it idles rough. When i floor it in park it hesitates sputters backfires and at times dies. It is not even driveable to move up and down the driveway. It was trowing the code for crank position sensor. I changed it. Ran good for bout 4 hours and started again. I'd take it out and wipe it off. Then it would run ok. For a little while then start again. Now i can't drive it at all. I took the sensor back and they replaced it but no help. Any ideas??:banghead:

Start with fuel pressure. Ignition in RUN position, engine off, fuel pump running, pressure must be 60 to 66psi. Pressure must remain above 55psi for 3 to 5 minutes after the fuel pump shuts off. Post your results.

sometimes you can turn on ign three or four diffirent tikes until you hear fuel pump then shut ing off and do same thing 3 or 4 times before trieing to all the way ingaging on switch..did you do a full tune up on this yet? to me sounds like its timing may have jumped or plugs wires crossed or coils

try this see if fuel pump is bad turn key off and on three or four times until you hear that click when fuel pumps all the way up. then turn ing to start and see if it starts.i dono sounds like it may have jumped timing.

well there is black smoke coming out my tail pipes it straight piped with a z28 cat. So there is a lot of black smoke

Are all the O2 sensors still in place?

yeah

If the fuel pressure regulator or fuel lines in the plenum are leaking, you'll get black smoke, guaranteed! Have you checked fuel pressure and leakdown rate yet? Those two tests will tell you in a heartbeat if the problem is fuel delivery related.

Here's where you check the fuel pressure with a fuel pressure check kit available at most chain type auto parts stores,

http://i131.photobucket.com/albums/p288/Clunk_/Image026.jpg