I'm trying to acquaint myself with the ins and outs of throttle adjustments...am looking at FSM 30-1010 and 30-3402. My 95 E300D is in the shop right now getting its weak acceleration and black smoke diagnosed. I suspect a clogged cat or maybe stuck-open EGR. BUT a nagging question I have has do with how the throttle is adjusted.

When I got the car, instead of a proper throttle guide it had a makeshift piece of metal screwed into the part in which the throttle guide should sit. So I removed that and replaced with the guide. But when I did that the idle was too high. So I adjusted the nut on the cable to reduce the idle. But now I'm wondering if, in my fiddling around with things, I created the problems I'm experiencing. I also notice that the spring that's supposed to be in the assembly is missing. In event, my problems surfaced immediately after replacing the guide. Coincidental or causal?

So there are a number of variables. Can you guys help me get a basic understanding of the various adjustments and what the symptoms would be if particular things aren't adjusted correctly? Thanks so much.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 159k miles
06 E320 CDI "Rutherford", Black on Tan, 178k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 145k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 75k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife