About Last Week My Rpm Started Not Working And Then When I Try And Fire It Up The Car Backfires And Struggles To Turn On It Takes A While But It Fires Up The Car Has The Same Power. I Already Replaced Cam Sensor, Crank Sensor, And Still Has The Same Problem All Fuses Look Good Checked All The Grounds And Were Good I'am Thinking It Could Be A Coil That's Messing Up Or A Ignition Problem Has Anybody Had A Problem Like This Any Help Is Appreciated I Just Want To Get Rid Of This Problem.it's A 99 Ls1 Auto.

 

did you install an aftermarket tach or shift light? If so check all your connections. Also, check your ribbon where the harness connects to your dash panel.

 

Did you check the grounds on the back of the driver's side head? They are easy to miss.

 

Does the engine make any knocking sounds? This happened to me, and the cause was the cam bolts backing out and the cam backing up far enough that the cam position sensor couldn't see it. It all added up to a rebuild when the cam bearings were hosed along with the cam, the lifters, and tons of metal shavings in the oil pan.

If it's not that, the cam position sensor might just be hosed.

 

No Aftermarket Tach Already Checked The Ground And Wires Back Of The Driver Head Everything Is Good There. It Has No Knocking Noise When The Car Is Cold The Car Struggles To Fire Up And Backfires Sometimes But When The Car Is Hot The Car Starts Right Away It's Just Weird How It's Happening.

 

If the tach's not workin', then I'd check both the cam position sensor and the crank position sensor. Either could cause what you're seeing, I believe.

 

make 100% sure that the ground going from your alternater to the driver side frame rail is ok and not broken or rusted or the bolts are loose... 99% of the time this is the cause of the problem you are having.