1986 244 M46 stick w/ ~ 190K miles (1-owner car with history of regular service). Started and ran well. Only running problem it had was a stumble sometimes - almost as if it was cutting out via a loose wire.

Cleaned throttle body, flame trap and breather box as part of normal service. When restarted idle was ~ 2000 RPM. Sensors under manifold still hooked up (checked via advice here). Removed throttle body & MAS again. Found holes in air-intake hose between MAS and engine and replaced the hose. I could have damaged it the service but holes look old so I think it's been like that - and ran fine.

Throttle plate seems to be closing correctly. No missing or broken vacuum hoses.

Now when it starts the idle goes up to ~ 1500 RPM but returns slowly to normal. Mild throttle pressure causes idle to go up and return slowly. A tap to the pedal causes the idle to return right back to normal. This seems top indicate a problem in the throttle body/ linkage (rather than a sensor or broken wire causing a high idle).

The new thing is that it is hard to start: Cold or warm it takes 3 5-second tries before it fires. Cap/ rotor/ wires are good. Spark is strong. While checking I did find a lot of white powder covering the spark plug ends and inside the wires.

I swapped the throttle body with a known good one from another 86. No change.

Since the hard starting and high idle began after the throttle body cleaning I believe they are related.

I think that either the TPS or the throttle linkage rod is out of adjustment. I was reluctant to adjust them until I explored other possibilities. I do get the click from the TPS on slight movement but it feels like it may be coming a little too soon.

High idle and hard starting could be a throttle plate not closing. Although it's odd that when the throttle body was swapped from car A to car B, car A still wouldn't start or idle well while car B is unchanged - still starts and idles fine.

There are several threads here about high-idle after throttle body service and most seem to be resolved after a TPS adjustment so I'll try that this morning.
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a few 1985-92 240s & 245s - parts cars & drivers