have they check the timing on it. sometimes when timing is off by a few degrees it would cause both rough idle and backfiring. also check for a dead cylinder.
Exhaust leaks close to the engine.
when my dodge stratus started to do that it was because I needed transmission fluid.
It would be very rare for a P1684 code to turn the light on.
Could be a number of things CONSULT with with your Dealer and have it looked at.
It might be that your pcv valve is plugged or the egr valve is sticking.
Loose belt - will sound like a screeching noise.
Failed fan motor, relay, wiring, fuse, computer.
If if starts bubbling even if the engine is cold, most likely blown head gasket. If only when engine warm, stuck thermostat.
Well a lot of them have the same engines & transmissions; but if you have a lot of people you'll be driving around, you'd want the grand caravan...The only difference is the length. I would go with the standard size, it'll probably get better gas mileage and cause less wear on the transmission & engine.
Low trans fluid, or internal trans failure.
Noises are impossible to correctly diagnoise unless you hear them. TAke it to a good diagnoistition.
parking brake on.
Failed radiator transmission cooler.
After reading the codes, with a scanner. You repair cause of code, and then can reset code with the scanner.
There are several complications that can cause a 1999 Dodge Caravan to shut off while driving. Most common issues include ignition problems or fuel delivery problem.
check the motor mounts
Fix the cause, or keep adding fluid.
Bad Throttle Position Sensor
There are pages and pages of things that can cause a check engine light. You need to have it checked with a scantool. Then the code can be diagnosed and repaired.
Fix the cause, use a scan tool, or unhook the battery.
A bad cam or crank sensor can cause a no start, but the engine will still crank or turn over.
The most likely cause would be low fluid level.