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I have read one of your answers on your website where you diagnosed a running problem. Their problem was the engine would “buck” around 2000 RPMs. You suggested replacing the oxygen sensor and that repaired his problem. I thought that would repair my problem, I have replaced all 3 of my oxygen sensors. Yet, I still the same problem with bucking at Highway speeds. I have a 2000 Chevy Blazer, 4.3L. It runs great except at 2000 RPMs were the engine “bucks! I checked for codes and it is giving me a PO300 (random misfire). I also checked the fuel pressure at the rail, and it is fine. Is there any chance that it might be the air flow sensor? Is there any way to check it without buying a new one and replacing it?

I wish I could answer your question with one or two words! All I can do is guess what your problem is. I do know on this vehicle the injectors will become somewhat restricted and MAY cause the random miss-fire code you are describing. This may be the "Miss" or "Buck" at highway speeds you are describing in your letter. I really think you need to seek a professional independent shop to help in determining what your problem(s) may be. The shop you choose with the right equipment is going to look in the following areas. 1) They will look at the long term and short term fuel trim to determine if the vehicle is running "rich or lean" 2) They will confirm this condition by sampling the exhaust gases coming out of the tailpipe 3) They will know the fuel pressure, volume, static, and wave pattern signature of the fuel pump. 4) They will research the internet to see if there is a "Computer re-flash" or "Computer up-date" needed from the manufacturer to take care of this problem. 5) They will verify with their equipment which cylinders are missing, causing your “bucking” So find a shop that has the right training and equipment to repair your vehicle "right the first time!" To find a professional independent repair shop in your area look for ASE Master Auto Technician Emblem. Check with the local BBB and the Chamber of Commerce. Ask them if the business you are inquiring about has customer complaints that have not been taken care of? Do they offer a 12 month nationwide warranty or just a local warranty? Once you have done your homework then go by and visit them for a test drive to verify your problem. Make sure they take the time to listen and understand your problem that you are having. Look around and see if the shop is clean and organized. If the shop dirty and cluttered they may treat your vehicle the same way they take care of their shop. Goods automotive repair shops aren't expensive, they are priceless!


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