I recently bought a 1983 245 B23F manual 4 speed and I've been having ignition issues, runs great mostly but then stumbles, misfires, surges. It doesn't stall or fail to start, it just runs ruff at times. Hot or cold. Checked the main wire harness and found it has the new harness PK 3515397 PO. Checked the Ignition harness, removed it from car and removed all the harness wrap. Inspected every inch of every wire and found no problems. Re wrapped harness with scotch 88 high temp/thick tape. Found that a previous owner had installed rebuilt ICU pn 8111226. Volvo says it should be pn 8111229. Don't know what the difference between these two ICUs is or if this could be causing the problems. I think that 8111226 is for an auto transmission and 8111229 is for a manual transmission. Can anyone shed some light on this?
Jay

 

Found 3 problems that each contributed to the mystery intermittent lousy running issue.
First, discovered that previous owner had replaced ignition coil and it was the wrong coil. It would over heat and fail intermittently. Replaced it with proper Bosch coil. Things improved. Noticed that now it would run better on top half of tank.
Second, the in-tank fuel transfer pump had died and the two inch long fuel line just above the pump had rotted out and was full of holes. When tank was below half full this caused fuel to have bubbles and then starvation. Replaced transfer pump and 2" long hose in tank. Things worked better but still would have horrible bouts of no power and terrible backfiring. Replaced ICU with ProgRama rebuilt. BINGO. Runs like a SINGER sewing machine.
Also, whoever designed the electrical connector for the ICU should have been shot! Those ribbed condoms (pin contact sleeves) that go between each of the male pins and female connectors are a pain in the ashtray. Replaced the harness plug with one off a '90s Chrysler, superior design, no "pin contact sleeves". Be advised that if you try this you will need to modify plug a bit, pin outs are different. Feel like ROCKY at the end of #2...Yo Adrean...I did it!
Jay

 

More info on ICU. The failing ICU that I replaced was a programa 8111226 which is readily available and is supposed to be for cars with automatic transmissions only. My car has M46 manual 4 speed with OD. Volvo and Programa said my car with manual transmission needs 8111229 which is UNavailible. No one could tell me what the difference between the two ICUs was and basically said that my intermittent problem was probably due to having the wrong ICU installed. Well the right ICU (8111229) was unavailable so I took a chance and tried a rebuilt 8111226. It works fine. Looks like I won't need to take a language course at the community college. I've become quite fluent in Swedish curse words. I tip my hat to the writers of countless entries in this forum and to Mr. Dave Barton for the insight that eventually led to the resolution of this puzzle. I would also thank God for answered prayer but that's probably not politically correct. This car has been a real challenge but I love it. Like Dave says, Volvo owners aren't quitters.