The car is old, I know, but it only recently started doing that... When it's in park, and the engine is on, there is a non-noticeable shake, but when it's in drive, and I'm stopped at a light the car shakes like crazy. It's so noticeable that people beside me stare at the car. My question is: What is causing the car to shake? and why does it only happen when it's stopped in gear?
If it is the 5E engine, they don't have a MAF. they use a Manifold Absolute Pressure sensor (MAP). SOME of them actually came with a 7A engine which did use a Mass Airflow Sensor (MAF). You can do a little research on it, but you'll find that Wikipedia won't tell you that.
Shaking is most likely motor mounts. The rubber in Toyota mounts is known to go bad very quickly (Nothing against Toyota). The easiest test to determine this is to put the car in drive and hold the brake. Lightly tap the gas. The engine should rotate toward the firewall. If it actually makes contact with the firewall or moves more than two inches, the mounts are bad. You also didn't state if it was an automatic or manual. From personal experience, they tend to shake A LOT at idle when the mounts are bad.
If your distributor is off by a little it can cause a misfire. You can rotate the distributor a little bit to adjust timing. This will cause shaking as well. You need to take some time test the compression, timing, and make sure you have no vacuum leaks.
If you hear loud ticking and knocking, you may have a piston ring or piston rod issue. Ticking only, would insinuate you have an upper end issue. A bent valve or collapsed/ clogged lifter would create that noise. You also need to use a feeler gauge to test clearances on that motor. They have hydraulic lifters, so you need to make sure they are within specification.
Lastly! Believe it or not on those cars bad springs or shocks can cause the car to shake quite a bit. I'm not sure of why this happens, but I'm a Toyota enthusiast and many of my friends agree. When the struts start to decay it can cause that extremely annoying shaking at stop lights. My 91' Corolla started shaking at idle. My buddy told me to check out the struts since my motor mounts looked good. He was spot on, my struts were well overdue for change. He simply told me it was just an old Toyota problem. "The way they design the chassis".
I hope this helps you!
I hope this helps.