[1990TS]

It would really help you would mention the year model and engine. Engine code (8th digit of the VIN number) would be even better. But anyway, I guessing your working on a 86-87 vintage 3.8 , most likely a VIN code "B" and you replaced the factory plastic/aluminum cam gear with a steel aftermarket gear. These aftermarket steel gears don't work in these engines the magnet for the cam sensor isn't isolated enough from the steel gear and the cam sensor doesn't get the proper interuption. Solution: Install a OEM GM cam gear like the car came with and your problem will be solved. The only other thing that may have happened is if the original timing chain and or tensioner broke before your replaced it, you may have bent the valves and now there is no compression. The old 3.8's (86-87) before the 3800 series vin c engines came out in 1988 were good for breaking the chain at 90K miles and bending the valves.