I have a 2000 Dodge stratus that won't change

if now it won`t start it could be a spark(ignition)problem, check for spark at the plug. you should check for a code in the pcm this may help, not all codes set the check engine light. could also be a bad fuel pressure problem.

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Make sure it's getting fuel. Try using some ether or starting fluid. If it rumbles to life but doesn't stay running then there's a problem with the fuel delivery system. i.e.... Fuel pump, clogged filter, pressure regulator.... If the ether doesn't change the results you are getting now then it's a fire or sensor problem. Ignition coil, relays, sensors not signaling, PCM... I wish you luck. Let us know how it turns out

engine won't crank, or won't start ??

probably out of freon have it checked for leaks

Must not have been much of a mechanic. If the engine runs and sounds fine sometimes and other times it doesn't then it does not sound like a mechanical problem with the engine. Sounds more like a issue with either the ignition system or fuel system.

Sound like a short, bad connection to the tach. Check that wiring before you do anything else. Had this problem on a chevy

sounds like to me the catalatic converter is plugged up, usually if you cant get an engine to rev anything over 2000 2500 rpms it has a breathing problem... its a real good possiblity its the converter causing your problem, especially if you had problems with another engine at any time, with like antifreeze issues, or fuel issues.. it goes strait to the exhaust and out the tail pipe.
hope this helps

Just check the transmission oil levels first, if they are low this will stop it from engaging into gear.

When was last fluid & filter change?