srosie

Check engine light went on b/c of a faulty vacuum hose clamp. Solution: replaced hose clamp. Tip upshift malfunction was suposedly fixed by replacing the gear shifter cover - something to do with a magnet underneath? I'll let you know.

srosie

The other possibility is a vacuum leak. All air entering the engine must be measured. See my article on The Air Intake System Any unmeasured air entering the engine will cause a lean fuel mixture and will result in a rough idle. Check all the vacuum lines and hoses and make sure they are supple and have no cracks. Also make sure they are connected tightly. If the hoses are stiff or have little cracks in them, replace them. Also be sure that the lines are connected to the proper devices. There might be a Vaccum Hose Routing Diagram under the hood that will help you make sure the hoses are connected propery. As a Scottish Chief Engineer once said: "The more they overtake the plumbing, the easier it is to stop up the drain."

srosie

How can we tell if the engine is running lean? There's a simple way to check, get a can of carb cleaner with a straw attached to the nozzle. Start the engine and unplug one of the small vacuum lines on top of the intake. Stick the straw into the fitting on the manifold and squirt some of the carb cleaner into the manifold. Not a lot, just a quick squirt. If the engine smooths out and the RPM's go up. it's running lean.

Some other causes could be a bad oxygen sensor, bad Air Flow Meter and a bad Throttle position sensor. All of these should throw a code in the computer lighting up the Malfunction Indicator Light (MIL)