I've recently changed the starter, battery, positive wire, spark plugs and spark plug wires.
the truck starts fine but the rpms are constantly jumping. what could be the cause of this?
I have to ask... are there aftermarket ignition parts, sensors or wires? You can google 'tach jumping' and find that no specific thing causes this that any data has been compiled. There are 4 ways i have encountered the causes, and one , the customer was willing to pay his bill. You can research instrument pod issues and tachometer sensor issues and have it lead to clues about how yours is. But you have to know how yours is. The electronics can have redundant circuitry? or have those circuits missing that make it like OEM when it worked best.
Search Chevrolet C/K 1500 Questions
Chevrolet C/K 1500 Experts