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my car starts idles ruff for about 30 seconds to a minute then smoothes out on 1995 Chevrolet Impala SS

added a fuel additive, changed o2 sensors, cleaned mass air flow sensors, runs really smooth except at start

poss vac leak.do you have any eng codes if so post so we can adv
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3 more answers
You can try changing the fuel filter. A very dirty filter can disrupt flow and volume at start-up when they are starting to plug-up. You can also try cleaning the IAC (idle air control) to see if that helps.
I would like to check fuel pressure and maybe volume. Get the datastream as well.
Cold start morning roughness that clears up... possible leaking injector (over night or if you let it sit for a while), possible head gasket issue (coolant leaking into cylinder), possible oil leaking past valve seals (hence oil fouled plug until it clears up.

Check coolant level, has it dropped at all? Leaking fuel injector has to be tested with fuel pressure tested and some other stuff. The leaking valve seals... look at the exhaust, is there any coloration during the rough running? Black, white, blue? - Keep me in the look.

Eric Sevim - Co-Owner - ASE Master Certified Technician
http://www.aplusjapaneseautorepair.com/
San Carlos, CA 650-595-2277