'93 220CE Idle issue / Throttle Body Part Numbers

[CreosoteChris]

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Cross-post – apologies if I’m bending the rules here – but I’m not really sure that the previous location was entirely appropriate - asking EuroCarParts for advice on sourcing a TB from one of their competitors
http://www.mbclub.co.uk/forums/2015220-post933.html
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Hello – I’ve owned my 93 220CE for a few months now - so a relative newbie - and have just hit my first properly serious problem with it. As it looks like it’ll be expensive to fix, I’m looking for some second opinions / advice…

Without warning the idle speed suddenly dropped to a level where the engine was just about staying alive, but popping it into gear (car is an auto) stalled the engine. Managed to get it around to the local mechanic who took a look, reported that:
-He’d adjusted the idle speed to make the car less likely to stall, more capable of being driven
-I needed a replacement throttle body

The car is currently useable, once it’s on the move and the engine warms up (but getting away with a cold engine takes a few mins of warm up before it becomes possible). Trawling around the forums, I see that TB failure is a pretty common thing for aged W124s, so I’m pretty confident my mechanic’s diagnosis is right, and I need to look for a replacement – do you guys agree?

Anyway, if I’m facing the prospect of getting a replacement, then I’d like to make absolutely sure I get it right. The current TB is labelled as per the attached pic, with part numbers on the label as follows:

VDO: 408.227/110/002
Mercedes: 000 141 70 25

Tried calling Dronsfields (very big Merc breaker a few miles from where I live) who advised it’s a very common failure, and they have none.

I guess I could go for a BBA Reman refurb job, currently quoting £165 (though I note they designate some units beyond repair)

My other option is this ebay listing for a new item – expensive, but not the same sort of eye-watering expensive as the other similar units listed on ebay. The compatibility details with the ad report that it’s suitable for a 93 220CE (but does not mention further details - mine is auto, no cruise control). However , the part number is listed as 408-227-111-003Z, not 408-227-111-002 as per the label on my current unit

This page appears to indicate that the two VDO part numbers are interchangeable, and equate to the same Merc part 000 141 70 25.

Does anyone have sufficient familiarity with the vagaries of Merc and VDO part numbering to advise on this? It’s about to cost be a pretty big wodge of money, so all advice appreciated.


Thanks, Chris
93 220CE, auto, red / black leather, 101k, Manchester

 

[bolide]

How did the mechanic alter the idle speed? It's set by the ECU

I'd take it to an MB specialist for diagnosis. E220s seem to suffer TB problems. The first thing to do is to remove the rubber pipe leading to the TB and clean the throttle butterfly & bore very carefully. It's hard to get it completely clean but the cleaner the better

There's a little air bleed hole by the butterfly in the closed position which I believe is the air bleed when the car is idling. This allows a certain amount of air through even with the butterfly closed. On cars with cruise control the TB has a magnetic clutch to hold the butterfly open, to set a cruise speed or to regulate idle.

How this interacts with the air bleed I don't know, but I've had a 280 with cruise with a bad TB that wouldn't idle. Replacing the TB (and the cruise ECU) cured the problem

The other typical fault is degraded wiring from the TB to the connector. It's possible to remake this if you're handy with a soldering iron

Based on the results I've had buying from Dronsfields I wouldn't buy from them again

Nick Froome

 

[CreosoteChris]

OK, I’ve made some progress here – thanks to Nick for his comments and suggestions.

Removed the TB today and sprayed it liberally with carb cleaner (STP brand, certainly shifts the accumulated deposits pretty impressively), working it over with a paintbrush, then bolted it back on. The unit seemed to be in pretty good condition, certainly no signs of cable damage or crumbly insulation.

The good news
- Car now idles immediately when started, even stone cold at zero degrees ambient, and does not stall when put into gear (even reverse which was previously a guaranteed stall with a cold engine). Start-up idle speed is 800RPM.

The bad news
- After warm-up, the idle is now consistently around 1300 revs (before it was highly variable, sometimes trying to settle at well over 2000, and requiring a blip of the throttle to bring it down to something reasonable). It’s also smoking quite a bit when on idle.

For anyone interested in this subject – there are actually lots of videos on YouTube posted by a bloke in Brooklyn, NYC, who operates a repair service. Here’s one dealing with bench-testing a ’96 C220 throttle body he’s repaired https://www.youtube.com/watch?v=Pyncnd0E2YY (many others available from the same poster, dealing with the different variants of the VDO TBs). So if you want a crash course on understanding this subject, spend a couple of hours watching a selection.

If anyone has any bright ideas about how to deal with my residual issue, then let me know - but this update is mainly as a courtesy to the community / permanent record for future ref. Will advise if I manage to get it properly sorted.

Regards Chris

 

[grober]

Throttle body

408-227-111-003Z

VDO Throttle body
Engine Code: M 111.960
Electronic, Mechanical, Article number of recommended accessories: Dichtung/Gasket: n/a, without gasket / seal, Ø: 57 mm
General Information:
Observe the specifications of the vehicle manufacturer.
Mandatory - check new part against old part (in particular O E No.)
Supersedes:
- 408-227-111-001,
- 408-227-111-002,

VDO Webcatalog

USE THE SIMPLIFIED SEARCH TO CHECK THE ABOVE

 

[CreosoteChris]

Thanks for that Graeme - at least I can now buy the eBay item with confidence - if it comes to that.

One possibility that occurred to me this morning whilst driving to work, is ECU “learning” – something I previously encountered when discussing a car I used to own (’85 Celica Supra).

On that car, the ISCV (Idle Speed Control Valve) settings were determined by the ECU every time the car was started after battery disconnection – you could actually hear it happening. When the car was started, the ECU would realise it had no saved ISCV settings, then make adjustments to the valve, and measure the engine revs until they got to the right value. Subsequent start-ups with no battery disconnect,. It just used the saved settings.

Guess I can test that aspect by disconnecting the battery and seeing what happens subsequently – but if anyone knows, please comment.

Regards Chris

 

[CreosoteChris]

How did the mechanic alter the idle speed? It's set by the ECU

Spoke to the mechanic today and he confirmed that, in order to make the car driveable after my initial problem appeared, he adjusted the linkage (metal rod that connects to the butterfly actuator, threaded with 8mm locknuts both ends). This can be lengthened to the point where the butterfly never closes fully. So I’m going to play with that when I get time / daylight, progressively reducing the length of the linkage and observing what happens. Should be within the next couple of days, weekend at the latest.

It’s now been over a month since my initial problem appeared, and my memory is fading… please can someone advise what should be the correct idle speed for a CE220 auto, with the engine fully warmed up?
- In Neutral?
- In Drive with the brake on?

Thanks, Chris
93 220CE, auto, red / black leather, 101k, Manchester

 

[grober]

IRRC should idle around 800rpm depending on load alternator air con etc but the engine ECU should be able to stabilise it thro the throttle body and injectors. Start your adjustment from a situation the engine is fully warmed up and under no load conditions.
One "off the wall" potential problem might be if your catalytic convertor had partially collapsed internally which would induce enough undue back pressure which the idle control might not cope with? Unlikely but its been known. This would also be likely affect performance and fuel consumption also so if these are OK you can probably rule it out.

 

[CreosoteChris]

Thanks Graeme

As far as I can tell, the current symptoms that I have are consistent with a combination of

(1) Fixed TB
(2) Throttle linkage length set far too long as a temporary workaround

So I’m reasonably confident that I can get back to properly-working idle by a straightforward process of trial and error. We’ll see. It’s bit hard to understand why cleaning the TB resulted in the idle control function (which seemed completely absent before) coming back, but I’m not complaining.

It’s a bit of a manic depressive business running a 22-yrear-old vehicle – seemed a few days ago like things were going wrong faster than I could get them fixed, the car was a total PITA to drive, I was beginning to wonder why I was beating myself up…

….but with the idle 80% fixed Sunday, stereo / aerial / interior lighting yesterday, I’m actually making headway. The car is now pleasant to drive, it’s a stylish classic pillarless coupe, gorgeous leather interior, superior exclusive retro-chic vehicle – I’m beginning to remember why I’m doing this.

Still need to deal with cabin heater blowing permanently hot, and an oil leak (job for the mechanic) - but things are definitely looking up.


Cheers, Chris
93 220CE, auto, red / black leather, 101k, Manchester

 

[grober]

Cabin blowing permanently hot could be a heater control fault but more likely a duo valve sticking problem. Lots of posts about this if you do a search

 

[CreosoteChris]

Yeeeessss!

The procedure was easier than I expected

- Threaded metal rod component of the linkage needs to be set just short enough so that the butterfly snaps shut completely against the stop (which kinda makes sense – it’s basically passing idle control back to the ECU and the electromechanical bits of the TB)

- I also had to slacken off the inline cable adjuster for the linkage a bit – looks like the mechanic also adjusted that for his keep-me-driving temp workaround

But back to a properly working idle setup, hot or cold, no stalls, no stupid 1500RPM idling – and no expensive replacement of the TB assembly. Total cost = £5.99 can of carb cleaner. Result!


Thanks to anyone who’s taken an interest (even those who’ve not responded, because just having the community here is a great encouragement to amateur tinkerers like me)


On to the climate control – will post in the appropriate section where necessary or informative


Cheers, Chris
93 220CE, auto, red / black leather, 101k, Manchester