I have a 89 camaro rs that runs fine at idle but going down the road you here a slite ping like when you run cheep low grade gas then the cheak engine light comes on then you lose power to about 1/2 but as long as the engine light is on there is no ping.I have spent 500 dollars on sensors not yet fixed problem can any one help???

did you do the knock sensor???

yes i did replace the knock sensor and the throdle pos sensor and oxygen s. i was wondering what it would act like with a partially clogg cat?

What is the ignition timing?

a clogged cat will make it ping as it will increase internal cylinder temp because of not letting the exhaust out...can you get it scanned???that would be helpful in the diagnosis...

EGR valve will do that too.

thanks for the help guys i will try cheaking the egr valve or see if cat is cloged if that dose not fix it i'll post it thanks again....