Looking for classic M-B oppos (I know you're out there!) *High Idle Hell*

"66671 - 200 [METRIC] my dash" (66671) 11/19/2018 at 22:02 • Filed to: None

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Currently looking at this 1989 420SEL for $3,000 cdn, been talking to the owner, and it suffers from “high idle hell”, which is apparently a common theme among these types of cars. He says it will idle at 2k rpm for a few minutes:

“Starts after couple of pushings of gas pedal and requires to hold it at around 2000 rpm for few minutes as they are fluctuating looks like idle control valve/solenoid”

He also says the RPM is not affected by weather.

Should I just stay the hell away? Haven’t seen the car yet and the owner says that’s the only major issue (also seat belt SRS sensor periodically but I’m not too worried, just want the car to drive ok). It has almost 300,000 km, but I saw it online and the colour has me in a trance!

I might go for a test drive this weekend, and I’ll see where I stand until then, but hopefully anyone can help me with this one thing.

Thanks!

Nibby > 66671 - 200 [METRIC] my dash 11/19/2018 at 22:19

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if you see it in person, regardless of if you buy it or not, pls take pics

fintail > 66671 - 200 [METRIC] my dash 11/19/2018 at 22:28

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That could be the issue, I recall these cars also have a “fuel distributor” that can cause issues, and that if you smell fuel, that’s likely the problem. I once had a W126, but it was an I6 model.

These cars have both amazing build quality and amazing expense potential . Fortunately, they don’t seem to be too hard to work on, just gotta buy the parts.

Spamfeller Loves Nazi Clicks > 66671 - 200 [METRIC] my dash 11/19/2018 at 22:41

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His initial diagnosis is actually my initial diagnosis as well; high idle is almost always the idle air control valve. Not being affected by weather does indicate it may be something more complex, but not necessarily . Different IAC systems behave differently. (e.g. Ford IACV fault will idle higher when colder, Chrysler IACV fault will stumble when cold or ignore completely, etc.)

I would find a local M-B indy with experience and get a quick opinion from them. Or better still, a PPI if the buyer’s willing. (Especially since if they do the PPI they’ll probably give you a bit of a break on the repair.) 

66671 - 200 [METRIC] my dash > Spamfeller Loves Nazi Clicks 11/20/2018 at 04:21

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Yeah, I’ve looked at forums so if I plan to go forward I’d know who to go to for a PPI. Still have to contact them but it’s early right now so I’ll have to do that.

I’ve read about the IACV/ICV and I’m assuming they’re the same thing? I’ve read a few guys have soaked/ cleaned them with brake cleaner , and it solved their  problem. Just hoping a good cleaning will do because the part can be expensive if new, but maybe I could find a used one for cheap? Hoping it wouldn’t have to come to that if cleaning is all that’s required. For now it’s just speculation anyways.

66671 - 200 [METRIC] my dash > fintail 11/20/2018 at 04:27

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Yeah, the build quality reputation drew me to some of these older Mercs.

For now, until I get any further I am contemplating if I want to risk my financial dedication to this/a car. I live pretty close to work but I want to be able to take the car out and enjoy it. I’ll have to see what the PPI has in store for me, and until then I can’t really do much else.

fintail > 66671 - 200 [METRIC] my dash 11/20/2018 at 09:23

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The expert analysis will be key, that, and if the owner has records to show it has been treated properly. These cars can soldier on for a long time with neglect, but when they go, they go big.

I’d save up and buy the nicest one I can afford, but sometimes the right project comes along that is too cheap to resist.  As long as the engine and transmission are sound, and it isn’t rusty, most other ailments can probably be cured with DIY time, assuming you want to wrench on it yourself.

66671 - 200 [METRIC] my dash > fintail 11/20/2018 at 12:09

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Well this would be my first car owned by me, and I’m thinking maybe wouldn’t be the worst car to start and learn some basic wrenching on? If the car has to sit I can still get to work so that’s a non issue for me, but I do want to drive it, maybe just not as often during the winter.

A for th e current owner, he says the engine and trans are solid, i'l l see what the PPI might bring, but he doesn't have records :( I'm curious as to belt/chain and tensioner condition as well.

fintail > 66671 - 200 [METRIC] my dash 11/20/2018 at 14:17

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I think this isn’t bad in terms of repairing electrical system quirks or even minor mechanical issues - n othing should be too buried, and it isn’t too computerized. It is very simple compared to a 21st century car, even simple compared to a W140.

It is at the mileage where timing chain and related parts can have wear. Definitely a good idea for the PPI, even on a car this cheap. One powertrain component failing would render it a parts car or long term off-the-road project. Also, if it isn’t a local car, look for rust, it is at that age, and these can go in harsh climates.

66671 - 200 [METRIC] my dash > fintail 11/29/2018 at 20:53

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I saw the car, and tbh kind of made up my mind when I saw some primer spots covering the rust on the body. The underside looked clean but I was hoping the exterior would have looked a bit better. Going to hold off buying a car until closer towards the end of the winter. Thanks for the help!

fintail > 66671 - 200 [METRIC] my dash 11/29/2018 at 21:29

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Good decision. As you probably know, rust can be a neverending battle, especially if a car isn’t kept dry.  It’ll be cheaper in the long run to buy a car with fewer needs.

Rustiest W126 I have seen came from eastern Canada.