bad fuel economy

You need to pull the codes from the computer. It is OBD-I so it is very easy, but on a motor that old these problems could be caused by several things each. I have no way of knowing what is actually going on from your motor from where I'm sitting or how well you take care of it, so I'll mention just a few probable causes.

High Idle: I believe your motor is throttle body fuel injected, so it is most likely an Idle Air Control valve not seating fully (dirty or broken), a cracked base gasket on the throttle body letting air in, or a bad coolant temperature sensor.

Shaking at Idle: Either a bad or disconnected knock sensor, bad plug(s) and/or wire(s), bad ignition module, cap, rotor, etc.

Bad Fuel Economy: Take your pick, everything from any one of a dozen routine maintenance items to something more serious - I have absolutley no way of knowing.

You are going to need much more help diagnosing these issues by someone in person than you will ever get over the internet.

Cheers - Jonathan

The car is multi port fuel injection. I take good care off it. Have used synthetic oil and have always changed the oil before 3000 miles. People give me a hard time because i take extra good care of it always. It does not use a dirtibutor (distributorless ignition system). The car has 100,000 miles.

Thanks for your reply, it might be time for another tuneup. It's been three years since the last one. But i did buy the expensive wires and sparkplugs the last time.

Thank you for your reply!

Myc1972