RPM GAUGE STAYS AT ZERO AND IDLES ROUGH AND JUMPS AND SHAKES WHILE IM DRIVING
Check your connections at the alternater. Sometimes the tach (RPM Gauge) is hooked up there. HTH. -Jim
I've experienced that with my cobalt's air intake, may not be your specific problem, but I took it apart and put it back together and it stooped jumping.
Search Chevrolet Cobalt Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Chevrolet Cobalt Experts