W126 300SE - 6 months on ...

[Shiskine]

Had my 1990 300SE for six months now and really enjoying it.

Still suffering from an intermittent stalling problem, where it stalls in drive when I pull up at give ways or when making slow 90° turns. Tends to be worse when warm.

Took it to my local independent who gave it the once over. He cleaned the rotary idle valve, re(set) clearance and cleaned the throttle body, but this didn't improve things. Apparently the distributor cap and rotor are in poor nick and need replaced. He's also recommended replacing the rotary idle valve, but has quoted me £196 for this part.

1. Does £196 for the rotary idle valve sound right?
2. I seldom get better than 19 mpg, although my journeys are all short hops; does this seem low?
3. He also spotted a broken NSF road spring - can't believe I didn't notice/feel this - and this will cost between £80 - £150 to replace; apparently they're colour coded but mine is so corroded it's hard to identify. Again does this price sound reasonable?
4. Does anyone have any ideas what may be behind the stalling problem?

 

[adam1977]

Had my 1990 300SE for six months now and really enjoying it.

Still suffering from an intermittent stalling problem, where it stalls in drive when I pull up at give ways or when making slow 90° turns. Tends to be worse when warm.

Took it to my local independent who gave it the once over. He cleaned the rotary idle valve, re(set) clearance and cleaned the throttle body, but this didn't improve things. Apparently the distributor cap and rotor are in poor nick and need replaced. He's also recommended replacing the rotary idle valve, but has quoted me £196 for this part.

1. Does £196 for the rotary idle valve sound right?
2. I seldom get better than 19 mpg, although my journeys are all short hops; does this seem low?
3. He also spotted a broken NSF road spring - can't believe I didn't notice/feel this - and this will cost between £80 - £150 to replace; apparently they're colour coded but mine is so corroded it's hard to identify. Again does this price sound reasonable?
4. Does anyone have any ideas what may be behind the stalling problem?

Nice looking W126, I considered one of those before buying my W140.

With regard to your stalling problem; it sounds like an idle control valve.... I have no idea where that would be on your car though

 

[allias]

Your mpg sound normal for that engine and your trips. I would say... do proper service with filters and others and you might gain 1-3 mpg.

On spring I would recomend to change in pairs. Less risk in getting wrong one as well as car sitting lower on other side.

PS Beatiful car. Congrats man.

 

[Sorry Pete]

Yep, 19mpg sounds about right for your use profile, and the winter won't have helped with the figures either. I managed low to mid 20's seeing a best of 27mpg on a long run, and I typically only did long journeys. Get it to an independent with experience of setting-up the KE-jetronic fuel injection used on these cars. I'm sure there's info on this site if you use the search button. A member uploaded a whole bunch of info specific to 80's Bosch fuel injection.

I had a broken front spring and only found out about it at MOT time, so yes , they can go under the radar. They should be changed in pairs, and they're colour coded with paint flashes relating to their different spring rates. They change with the weight of the car eg. I6's vs v8's, cars with more equipment, a/c etc... It works on a points system, and your merc dealer should give you a part number if you give them your VIN. They could be competitive with a price, or you could get the part number from the EPC and self-source.

Can't help with the stalling, but at a guess, the idle control valve/module(?) sounds about right.

It's a beautiful looking car, I still want one but I think I'm a w124 diesel convert...

PS. If you haven't done so, I'd invest in some rust preservation of the under sides of the bumper chromes. You don't want to know what they cost at the dealers...

 

[Shiskine]

Yep, 19mpg sounds about right for your use profile, and the winter won't have helped with the figures either.

That makes sense. It dropped to 15 during the really cold snap (-10°) we had up here.

Thanks everyone for the comments and the advice about replacing a pair of springs.

 

[ianrandom]

Very attractive car. I hate burgundy normally but thats lovely.
You could try a breaker for the idle control valve. Has to be known good though obviously.