got a problem with my '84 280E, euro m110 engine w123, auto tranny.

i'm having power loss while driving at normal speeds under normal conditions. pedal will just start acting like it no longer has an effect on the engine. no electrical issues or dimming but i will be driving along and all of a sudden the car will no longer respond to the pedal. it won't die out or stall, just no more power. take my foot off the gas and press it down again and i get a response, less than a second later. driving normally, something happens and i'm coasting for a second, put my foot back on the pedal, and i'm good to go again.

and, not sure if related, but i'm having serious stalling out issues while at stop lights or driving very slowly, like when i went to parallel park the other day. stalls out, put it in park, turn the key, and sometimes she'll start right back up again with no issues. the other day however, i sat in traffic for a full two minutes trying to crank her up to go and she wouldn't. a full two minutes later and she starts right back up and drives home like nothing happened. when restarting, she'll crank and try to get going, stumble a bit, then die. definitely not the starter or battery.

she's been in storage for a few months waiting for good weather. in that time i have replaced the plugs, wires, dist. cap, and rotor. valve adjust, new oil & filter, and air filter. re-did central locking system until working again, plus "new" vacuum brake booster and new vacuum line to the booster from the intake. all the fuses were replaced too, and she's got a fresh tank of premium gas.

yesterday i changed the fuel filter as i had one around. drove pretty well but still stalled when i pulled into a parking space. people have suggested a failing fuel pump and/or fuel pump relay. they have also suggested some kind of massive vacuum leak either involving the brake booster or a leak somewhere else. thing is, previous owner alluded to this issue when i bought it, though he said it happened much less often than this. either something is getting worse, or he stretched that info a little when selling. he thought it might be related to the brake booster, which was leaking and hissing when i bought it, hence the replacement.

anyone have any ideas? she's supposed to be my summer daily driver and i'm questioning her reliability at this point. need help quick! thanks!

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1985 300D - 1984 Euro 280E AMG Clone (SOLD) - 1978 280CE (SOLD) - 1983 300D (SOLD) - 1981 300D (SOLD)