The car is my '94 E320 wagon with 231,000 miles and lately, intermitently, it surges at idle to about 1,200 rpm when warm and sometimes feels like it cuts out on the highway for a brief instant then everything is fine. Typical things have been replaced on it one time or another like HFM harness and I had a tune up recently. I have a CE light that is code 26, 2-3 upshift delay which is the only known error message at this time. Can anybody throw some suggestions out? This is my daily driver with the kids so I would rather not get stuck somewhere.

__________________
dtf
1994 E320 Wagon (Died @ 308,669 miles)
1995 E300 Diesel (228,000)
1999 E300 Turbodiesel ( died @ 255,000)
2006 Toyota Tundra SR5 AC 4X4 (115,000 miles) rusted frame - sold to chop shop
2011 Audi A4 Avant (165,000 miles) Seized engine - donated to Salvation Army
BMW 330 xi 6 speed manual (175,034 miles)
2014 E350 4Matic Wagon 128,000 miles
2018 Dodge Ram 21,000 miles