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1997 993 rough engine idle


Vehicle Information: Year: 1997; Body Type: Convertible; Total Mileage: 16200;

My car runs great at every speed except idle. It has a rough idle or maybe it's a misfire. You can feel the misfire by putting your hand over the right side exhaust tip. Turn on the A/C and the rought idle and miss clears up. I have changed the fuel filter, spark plugs, oxygen sensors (before cat), checked all vacuum hoses, cleaned Isv valve,new K&N air filter, two seperate mechanics have done bosch hammer tests with no error codes revealed. The car idles at 800 and 840 with A/C on. I've read all the previous posts and searched the archives here and on rennlist and spent several months and dollars trying to solve this problem with no success. None of the above has made any difference in the performance of the car. The car starts easily and after warmed up and rpm drops to 800 the miss shows up. This car uses a quart of oil every 2K. Should these cars idle smooth? Am I trying to hard for perfection? What would you suggest next?

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