I notice that my work horse Camry 1999 is starting to shudder whenever I come to a stop and keep my foot on the brake while in drive. It feels like it will shut down but when I drive off everything is fine. Any suggestion of what might cause that symptom?
Check your brake power booster assist for a vacuum leak. It’s likely leaking.
I’m assuming you can reproduce this in your driveway. If so, then unplug the vacuum line from the booster and plug it (with your thumb or similar). Then have someone step on the brake. If there is no shudder, then that confirms it’s a leak in the booster unit.
Do you have any fault codes?
If not, start with the basics. Sparkplugs, ignition wires, rotor, distributor cap, that stuff (if this is a distributor-based ignition system). Go from there to testing the compression and, with a vacuum gage, checking for vacuum leaks. A vacuum gage will also tell you if the valves are creating unstable vacuum due to wear, tired springs, or whatever. You can also try cleaning the throttle body.
There are a host of problems that can cause uneven idle in an 18 year old engine. Most result from normal wear.
By the way, how many miles does it have? I-4 or V6?
Is the idle speed dropping too low at a stop with the foot on the brake? The idle speed should remain the same at idle no matter whether the transmission is in neutral or DRIVE.
I’m assuming the engine is about to die? Maybe an IAC valve issue as a possibility.
I assumed, maybe incorrectly, that the shutter you’re experiencing at a stop only occurs when your foot is on the brake pedal. If it also occurs when your foot is off the brake pedal, then I’d consider the above additional suggestions before mine, especially a dirty IAC.
It sounds like it is misfiring for some reason. As a start, when this problem is happening, check the battery voltage with the engine running, it should be at least 13 volts, and no more than 15.5 volts. If it’s not that you have some kind of problem w/the ignition system, low engine compression, or the air/fuel mixture is incorrect. You just have to go through those one by one until you find the problem. Most often this would be an ignition system problem of some kind; faulty ignition module, coil, or high voltage wire.
here is an $8 product that lets you monitor the battery voltage while driving. Great!
Try cleaning the throttle body mechanism.