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You need to properly re-adjust the throttle body, linkages and TPS switch. Here's a recent post with the proper adjustment procedures. Very simple to do and you'll learn a lot about your throttle body in the process so you can clean it yourself the next time (it should be done routinely, like every 2nd or 3rd oil change).
Your mechanic is obviously not overly familiar with LH-Jetronic systems. The ECU alone controls idle speed using the idle air control (IAC) valve. The ECU will try to maintain idle whenever the TPS switch indicates the throttle plate is closed. Once the throttle body is properly adjusted (like at the factory) there should be no need to touch it other than for cleaning. Tinkering with adjustment screws and linkages is just masking the basic problem and as a by-product will typically disable the TPS idle function completely. If the TPS switch is readjusted in an attempt to compensate then idle will be maintained, but the ECU will have a tougher time controlling the IAC over a smaller range and/or the valve will need to operate beyond its physical limits.
As almost everyone else has mentioned, the root cause of your rough idle is likely a dirty/sticky/worn IAC valve. So definitely attempt to clean it -there should be notes in the FAQ on how to do a good job.
For a poor idle, you're also looking for any source of unmetered intake air. You checked the injector seals as good, but if pressing down on them changes the idle then maybe the seals are starting to get stiff and in need of replacement. Carefully check for disconnected/split vacuum hoses and leaks at the brake booster vacuum fitting. Although there is a check valve, it's a good idea to try plugging off the vacuum lines for the cabin air control system in case there's a leak there. Remove the main air intake tube, carefully flex it and inspect all around for any splits in the bellows. Finally, make sure your ignition system is in reasonable shape, especially check that the plugs aren't fouled.
If everything else is in order and your idle problems continue then a replacement IAC valve may be in order -they don't last forever.
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Dave -940's, prev 740/240/140/120 Never overestimate what little I know.
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