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Since 2008 of May I have had a persistent check engine light come ON then OFF only after the problem was thought to have been fixed by the Chevy dealer. Light would stay OFF for weeks or months with no engine light when car codes have been diagnosed and components replaced, only for the light to reappear again. This has stumped this Chevrolet dealership service dept. in Acton, MA. for the last 1 1/2 years with my 1998 Camaro Z28 5.7L with 150,000 miles but running good 20/21 mpg 50/50 city/highway on average. In the last 1 1/2 years I have replaced the left side cats twice, aftermarket cats by Custom Exhausts in Reading, and went thru 6 O2 new GM sensors, 2 new GM air pumps, and still my engine light remains on (not blinking), this after 3 complete diagnostic scans by dealer with valid codes worked on by dealer too. Unrelated back in 1998-1999 under the mfr. warranty, I've had 2 fuel pumps in tank replaced along with a bad Map Sensor, and did not have an engine light come on until recently in 2008. I recently tried going back to 93 Octane after 10 years of using 87 Octane with no luck in turning off this persistent engine light that currently remains on. After 2 tanks of 93 and no success with it turning light off, I went back to 87. I get no Knocking with any octane. Dealer says to just keep chasing down the codes until it's finally fixed but this car is nickel and diming me to bankruptcy. Massachusetts has very strict annual car inspections. It's a shame a simple engine light can do in a great car that goes thru regular routine maintainence. In self-diagnostic road tests recently I notice all the time now that when I accelerate hard the transmission stumbles as if the air pump has gone faulty again. The automatic transmission runs great and normal around town but seems it can't get into high gear and stumbles and hesitates and is not smooth on hard acceleration only from 0 - 100, but the transmission will behave normally smooth when accelerating easily 0 - 100 mph. All fluids are up to level. Tranny fluids were replenished at 60,000. All 150,000 miles have seen only easy driving. With normal driving both city and highway the car runs great all around but with an engine light on. The general engine scans codes point back to the cat. If this is so, why did I run with no light for 7 months on this replaced cat. How can a cat be so out of spec that it plays havoc on the O2 sensors? New O2 sensors are also giving codes of low voltage too. If I replace the Cat with a G.M. replacement it will be a costly mistake if the engine light remains on and I've learned that GM does not make cats for this car anymore, so is there a way to bypass the cat or o2 sensors on diagnostic scans? some say I may have destroyed the knock sensors by using 87 octane since 1998. I do not hear any knocking noise. Can a pin hole leak in the Y pipe be welded closed too?
