Suspect low oil pressure for the light turning on. Have the actual pressure checked with a mechanical gauge.
The shaking is due to a misfire. It is common for engines to stall at idle from running too slowly. The last thing you want to do is ignore the Check Engine light, for two reasons. The Engine Computer detected a problem that is often very minor, but can turn expensive quickly. It will set a diagnostic fault code in memory that will indicate the circuit or system that needs further diagnosis. That is the single most important information that is needed to find the cause of the problem. That code will erase when the battery is disconnected, as many people do who incorrectly think they're going to "reset" something, and it will erase after a specific period of time or number of engine starts, if the problem doesn't get detected again. You lose that very valuable information when the code gets erased.
The Engine Computer runs a lot of self-tests on many circuits while you're driving. It compares many things to determine when something is wrong. When it detects a problem and sets a fault code, it knows it can't rely on that circuit to use as a reference for other tests, so it may not run them. There can be problems, such as you're having now, that will not result in setting a fault code. That means your mechanic may have to determine the cause of one problem, and give you an estimate based on what he knows, then wait for the next problem to be detected, and start all over with the diagnosis, and come up with a new estimate for more repairs. That's why they often get blamed unfairly for not fixing the problem the first time.
Friday, March 8th, 2013 AT 9:17 PM