Mitsubishi Repair: car wont stay idleing, throttle position sensor, sensor tps

Question
1990 eclipse 2.0L, GS, manual,turbo,  broke down & won't stay ideling, will only stay running with accelerator held down. Can hear a pinging noise, maybe coming from the top of the engine, souds like possible valve failure. Smoke coming out of tailpipe on take-off and when slowing down and then accelerating again. Took trip up to the mountains when this all happened. (Engine was rebuilt a few months ago!) Any ideas would be greatly appreciated!

Answer
Gregg,
Since you have a rebuilt engine, I'll assume it's not leaking oil from the valve guides or stems.  If the smoke you're seeing upon acceleration is blueish, then that could be oil coming from the intake manifold or even the intercooler.  Over time, oil will accumulate in the intercooler from the breather hose that connects from your valve cover to your turbo intake tube.  When enough oil builds up in there, it can get sucked into the intake, burn up, and cause you to see blueish smoke.  Another source of oil is from your PCV valve.  That is connected via a short rubber hose directly to your intake manifold.  Oily air being sucked in from there can cause noticable smoke.  If the smoke is dark grey or black in color, than that means you're burning fuel.  That's usually evident of a bad oxygen sensor or bad catalytic converter.  

Your poor idling may be do to a failing Idle Speed Control (ISC) motor; sometime called an Idle Air Control (IAC) motor.  When that fails, you'll definitely have a bad time idling.  in just about all cars on the road, it's just a matter of time before those go bad.  Some ISC motors can last 20+ years and other might last 5 years.  But it's easy to test if you have a service manual and a voltmeter.  Another item to check is your Throttle Position sensor (TPS).  That is easily testable as well with a service manual and a voltmeter.

If your engine is pinging, be sure you are using the highest octane available at the gas station.  Also, use a bottle of fuel system cleaner after the next 2 or 3 fill ups.  

If all else fails to give you evidence of your car's problems, check your car's computer.  Read this article for further information:
http://90gsx.com/eclipse/cap/caps.htm

If your ECU is failing you will start to notice starting and idling problems.  It's a good idea to check your ECU because eventually the capacitors on it will fail.
Good luck!