I have an '85 300TD with 140k miles. Car used to run very well but now idles very rough and knocks on initial acceleration for about 15 minutes when I start up each morning. Recently had the a/c compressor replaced and mechanic said he installed new relay (which I believe cuts out compressor upon accel), but I don't know if that has anything to do with my issue. (It runs rough with or without a/c on).

I have read a bit about running Redline DFC through and replacing fuel filters. Haven't done DFC but did filters about year ago. Fuel in my area is usually "fresh," if that is of queston.

New user here and appreciate replies.

The filters should be changed every year at least. Start there.

Fuel can look crystal clear but it still contains dirt and other XX micron sized particles that get filtered out.

If it smooths out after it warms up, you could probably use a valve adjustment too. It may be coincidental that the symptoms started after the work you had done.

__________________
Chad
2006 Nissan Pathfinder LE
1998 Acura 3.0 CL
OBK#44
"Pleasure in the job puts perfection in the work." - Aristotle (384-322 B.C.)

SOLD
1985 300TD - Red Dragon
1986 300SDL - Coda
1991 - 300TE
1995 - E320
1985 300CD - Gladys

It is unlikely that the a/c work is related to the rough cold idle unless the mechanic knocked something loose. The '85 does have some unique components related to vacuum, EGR, tachometer, and a/c function.

Is this a TD (station wagon or "T-sedan") or a DT (sedan/coupe)?

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

All the more reason why sedans are "D's" and wagons "TD's". Just don't need all the DT and TDT crappage.

Back to our regularly scheduled forum programming........

__________________
Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

nice use of word "crappage", btw.

__________________
1982 240 D, 308,000 - 321,127 miles (sold)
1982 300 TD,166,500 - 226,000 miles
1998 E 320, 120,000 - 144,000 miles
2005 C 230 K, 26,000 - 77,000 miles (sold)