can sporatic tach cause engine to stumble?
First post: My 2004 trailblazer 4.2 has started to have some issues. The Cam actuator and sensor have been replaced, but ever so often the tach will stay at zero when motor is running. The idle seems to be good (most of the time) even if tach remains at zero. As you accelerate the tach does rise, but stays 700 to 1000 rpm's less. Problem is this started and then transmission went out, replaced transmission and everything seemed fine for a week. Then tach starts this intermediate problem. It appears that if not driven a few days it works fine for a week or so then it happens again. Any way this tach issue can cause the motor to stumble or miss? only does this at 40mph+, and only if tach is having these issues. I have read most of the threads and it seems that everyone says replace stepper motor, which I plan on doing, just want to make sure I don't have more problems! Thanks in advance for your help