Got a 99 Z28 that has been running ruff for a couple of months and I can't figure out the problem. With the HPP programed with engine tunning it will staul out for a few secound and then rev back up. but when unprogramed it will run better but it is still running ruff and I believe there is a small power loss, but the check engine light dosn't come on. I have changed the spark plugs, and borrowed a MAF from a friend to see if it would help but no improvement, I have even tryed reseting the computer. So the best clue was that it got worse with HPP programmed. I need help, any sugjestions would help.

 

o2 sensors?????

 

anyone know the part # for the pre-cat o2 sensors, and how, much they cost?

 

are they different from pre cat and the other two????

 

I'm not sure... but now that i think about it they probably are because the o2 just take the reading and the computer takes the reading and decides what to do with that reading depending on which sensor it is (if that makes sence). I can try using the o2 sims that I replaced with the sims, in place of the pre cat o2's and see iF it helps.

 

i had a very similar problem- it turned out to be a bad #3 plug wire.

jay
san francisco

 

do you have headers? I have magnecor plug wires that only have 20,000 miles, but maby the heat got to one.

 

In a day i changed my spark plugs, changed the oil, then took it to have the transmission fluid system and coolant system flushed and it made a noticeable difference.

 

no, i don't.

however, the general's diagnostic equipement should be able to spot the problem, if that is what it is. the trick is finding a dealership with a service writer that doesn't want to charge you a bunch just to hook the car up to it.

jay
san francisco

 

Will it tell you whats wrong even though there is no SES light?