Engine idle when at operating temp

the car('04)was recently tuned by an authorized dealer— the car immediately idled rough at about 500rpm in Drive. I brought the car back several times and the problem persists, when the car is up to temp and in Drive.

500 rpm is too low.

Why did it go in to get “tuned”? Was there an operational problem? Can you elaborate?

the onboard computer noted we had a leak in the gas cap “service engine” light came on. we took the garage managers reccommendations to replace plugs, wires, brakes, etc. 150,000 miles on odometer. I kept bringing the car back to fix the rough idle – my smooth running car is no longer smooth running and the dealer doesn’t seem to be able to restore the car, at least to the condtion at which it arrived at the shop.

What, specifically, was done in response to the “service engine” light? And did it work? I.e. is the engine light now off?

The engine light is now off. The gas cap was replaced and the engine light went off. Because nothing was done to car for 150,000 miles except batteries and tires, maintenance work was recommended so replaced all belts, brakes, plugs, wires,etc. Replaced distributor cap on the third visit which seemed to work the first day but then problem reoccurred.

does the rough idle go away if you put it in neutral or park? Find out if they had to remove the intake plenum when they did the tune-up. if they didn’t replace the seals for the intake or had one fold up when re-installing you will have a “lean” condition that will cause a rough idle under load (in drive) and will worsen with temperature due to the plastic and rubber expanding and allowing more air into the mixture. Have them check your o2 sensor values and this should give them some idea of whats going on. if not have them give you the values and i Could let you know whats going on most likely.

the problem does go away when we shift inti Neutral or go to Park, and your advice sounds logical.

Than you for the help, I’ll forward your comments to the shop.