My 2002 chevy s10 zr2 rmp ga

[Samuel Sanner]

I need help with my 2002 zr2 s10 the rpm gauge jumps p and down about 1000rpm. Even if im at a stop. The check engine light also flashes if the water temp goes above 215°f.

[Niners 365]

 This can be a few different issues. Like I always tell everyone, start simple and look at fuses first and make sure you don't have a bad fuse to the cluster guage. I had one that my voltage meter kept pegging, replaced alternator and same results. Tested alternator, came to find out it was a bad fuse. One of the poles in it burnt and was hard to see. The guages are all a cluster guage, right now I have my digital milage display going in and out, but all the rest are fine. 2003 zr2 4.3 s10.  Check the cable that leads to guage cluster from end to end and make sure it is not loose or corroded Also if your temp is heating up, have you noticed overheating? Bubbling coming out radiator cap? These caps can wear after alot of miles. Sometimes it's as simple as replacing the cap. However, after 100,000 miles, the thermostat tends to go out, mine went out at 120,000. So did my head gasket and I had water going out tail pipe.