this happens about once or twice a day. so i want to find whats the problem with it.

1984 300SD

changed 2 month ago, primary and secondary fuel filter, ran a can of diesel purge. oil, oil filter, air filter.

maybe like once or twice a day i would come to a stop light and my idle drops down to around 500 RPM. as the light turns green i would put the pedal to the metal and the engine would go up to about 900-1000RPM and stay there. for like 4-5 seconds. so my car doesn't really want to go at all. after a couple of seconds (when it reaches ~2000RPM). it would go fine.

if i notice the drop when the light is red i pop it in neutral and rev it a couple times. i notice the engine will shake a lot. some times after a couple of revs it will clear this problem and it will take off fine.

just wondering what could be the problem. i always thought maybe the injectors are clogged? i ordered some dielsel purged yesterday. thanks for any advices.

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198? 300D ???K - Future DD
1989 300TE 285K - traded in '12
1984 300SD 186K - Sold in 08
1978 300SD 330K - Died in 05