I have a '95 SL500 with less than 53,000 miles. As you can guess, it does not see much use. Taking it out yesterday (sunny, temps in the low 40s), it began to run roughly at idle in Drive and shook a lot when starting off from a stop. Warm idle was running an indicated 500 rpm.

I got where I was going with the engine running roughly. When I returned to start the car again fifteen minutes later, it would not start. I cranked it twice for five seconds each time. I walked away, returned twenty minutes later, and it fired right up. The roughness at and off idle was still there.

I drove it for a while, and after about fifteen more minutes the roughness was gone. At no point through this did I get any warning lights on the dash, oil pres and water temp were fine.

The car usually requires a bit of cranking (say, three seconds) to start normally.

One other area of concern is oil pressure at warm idle in Drive. I have 5w30 Amsoil in the crankcase, and at a 500 rpm warm idle, my oil pressure is just over 1 bar. I do not hear any ticking from the engine, so I am not sure about going in to change the oil guides in the heads. Pressure goes right up to 3 bar as soon as the rpms go up a bit.

So, without throwing parts at it, was this just a fluke? A shot of bad gas? A bit of sulking on the part of the car because I don't use it enough?

Thanks!
Robert

i don't like answering questions like this but what the heck.
your oil is just to thin in my opinion. thats my thought and no science to back it up. need to get into the heavier stuff like mobil 1 15/50.
now as to the running, no idea. would see if it comes back and then worry.
you could get someone to test for codes. has to be a machine that can read pending stuff also.

george

Sometimes the "non-scientific" answer is the best one.

I too own one like yours, and my wife rarely drives anyway, so I try to take it out once in a while. I don't have the three-second start issue like yours, but the valve ticking does occasionally occur and then it goes away after 10 or so minutes of driving. The car sitting for long periods does attribute to this in a way. Different oil viscocities can improve it somewhat, but it will still happen from time to time.

I think the three-second start may be a different issue, like some sort of slight fuel pressure leakage from sitting for long periods of time. So on startup, it takes a little time for the system to develop pressure. The accumulator on my W124 performs this function, but I can't comment on the R129...after all, it has proven to be so reliable, that I haven't had to root around the engine compartment at all!

Try to take the car out a bit more (weather permitting). These cars are meant to be driven, and sitting for long periods of time will eventually get to the miniscule seals and such throughout the vehicle. A woman I know well has had her second coolant pump replaced on her 93 R129, and the car only has 8K miles!

Also, "real" issues that require attention may take several months to manifest on a rarely-driven vehicle, versus immediately on a daily driver...

__________________
2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car