L
lsimpala03
Guest
2003 chevy impala LS. When going up a big hill on the highway car will down shift and RPMs will raise to about 4500 and jump back and forth around that area. Then if I don't hit the break (to turn off the cruise) the service engine light will flash then turn off. I have replaced spark plugs, wires, coils, and fuel filter. My worry is that I did have a missfire and being stupid I ignored it for awhile and kept driving, now I am wondering if that missfire didn't clog my cat. conv. That is my next guess as to what is wrong...any ideas??? THANKS