So I've been calling around a bit on this rather annoying issue I have. Engine (W108 M130.980) won't idle properly when cold, has trouble keeping up its pace when cold, etc. Then when it hits 80 degrees Celsius, its operating temp, it will dive to way too low RPM's for like 10-30 seconds (you gotta keep it alive with the pedal). Then it idles totally fine afterwards. If you fire it up 4 hours later, it'll take a good 5-8 seconds of cranking until it fires. It idles a lot cleaner but it misfires on random cylinders.
Now I've been told some different stuff, but you gotta start somewhere. First thing is, the battery in my car is currently a 420 CCA (55 AH) battery. Apparently, the recommended is 680 CCA. The starter does crank over slow(er) than when it's hot by a good shot, but would it lead me to have idle issues when cold?
Option two would be the check valve (pressure holders) on top of the MFI leaking, causing it to not have any pressure when left over night. However I'm not really sure if this is the case, as it just fires randomly on cylinders when cold, no pattern as far as I can see. It also fires up quicker cold than partly hot (say sitting for 4 hours after being driven). So I'm pretty sure it's not a problem there.
What's most likely the case is the WRD sticking / blocked filter. I've been talking with a person who owns a 280 SL, and he says he can clearly hear the MFI / WRD sucking in air under cold starts. I don't hear this at all, no air seems to be going in anywhere near the MFI pump. I tried calling up a Mercedes classic specialist who told me "it's most likely the WRD and not pump related".
I'm thinking of just driving the 180 km there to get it fixed, considering I am terrified of messing with anything that has to do with the MFI. Pal gave me a great site (The SL113 site) which has some info on the WRD - I'd just like to hear if there's a way to test if it's the WRD and not the pressure holders.
I'm not touching the pedal in the first clip, however the hopping up and down in the revs seems to have seized after the CSV got a new seal, so it'd stop leaking petrol.
You can clearly hear the engine misfiring between 0:17 and 0:20. That's the first startup after 2-3 hours of sitting.