W124 94 E280 Idle problem

[ALC]

Hi @ all,
I'd be very grateful for any suggestions or help with a problem on a 94 w124 E280 i just bought. ( it had this problem on purchase, but there is a reason why i still bought it )
It has intermittent idle "hunting" .
All the usual stuff is ok, tried a replacement maff which actually made it worse.
Air intake is clean, no air leaks in hoses.
On my 3rd visit to a garage to run diagnostics however, its comes up with the message
035 025 CTRL SYS richstop/mix too lean - which means nothing to me either.
According to the manual, that fault code is actually an "Air Pump Relay" fault.

So. can anyone tell me where the airpump is, where the relay is for it, (if its not attatched)
I do have what looks like an airpump in the car, and did notice that one has a pipe connected to the manifold and the other side of this pump has be pipe cut and blocked with a bolt. So im hoping that is it.

If anyone can shed any light on this, or give me some other suggestions of what to check, i'd be very grateful, its my only car and used a lot.
my 1st post of many "help me" ones to come i imagine lol
merry xmas to all,
AL

 

[grober]

Looks as if someone's fiddled with the air injection pump and maybe the EGR lines also. There are a couple of solenoid valves associated with this system which are also powered from that same relay K17 which you will find in the main relay box behind the main fuse box. It should be marked which is which but looking from the front of the car its the small relay nearest the front on the left. There's a lot of plumbing associated with the emission system and as its been modified I wouldn't know where to start??

 

[ALC]

ok grober, thats a start actually thanks.
so now i know what that part is, my next question sir would be...
where is the pipe on the left from the air pump ( left in pic or the side nearest the glovebox ) actually connect to ?, as it is that side that has been cut'n'plugged.
Thanks
Al

 

[grober]

Have a look at the following pages here:- http://www.detali.ru/cat/oem_mb1.as...942&GA=722.433&GM=717.440&CT=M&Cat=520&SID=14

try to identify which valve you are talking about BY CLICKING ON:-
EXHAUST GAS RECIRCULATION
or
AIR PUMP
or
VACUUM SYSTEM 124

 

[kth286]

ALC

The picture you show seems like the purge valve.

Is it on the offside inner wing?

If so, it should be pulsed about once every second by the ECU once car is up to temperature (you can hear it click and also feel it by putting your hand on it).

The hose from this unit goes one way to inlet manifold and one way back to charcoal filter in the offside front wing cavity.

It is the petrol tank evaporative loss emissions system, and the fuel cap should be a sealed type.

You may not even have an EGR system or an air pump system - I do not on my car which also has the same 104 engine but with 3.2 litre capacity.

The air pump would be driven by the belt and is on the exhaust side of the engine - do you have the pump there?

The EGR is on the exhaust system - do you have that?

Let us know and someone will help you further.

The method of reading fault codes is very simplistic on these engines and I fear you may have used an inappropriate method leading to false conclusions.

Was it done by a Mercedes specialist familiar with that generation of car?

If not it needs to be.

 

[ALC]

great guys thx, nice to finally join a forum that has active and knowledgeable member. i do understand that its only advice and tinker at my own risk
so please feel free to drop any ideas info still, thanks

and no, it was looked at by 2 independant garages, who are not merc specialists...now i'm scared lol, i dont want a bill worth more than the car

 

[Howard]

Hi ALC,

Where abouts in the UK are you , perhaps someone can recommend a good Indy near you to have a peek at it .

 

[Dieselman]

It's probably worth checking the coil loom insulation hasn't degraded allowing it to short out.
If it's just hunting as opposed to missing suspect either sticky throttle flap or an air leak into the manifold. Clean the throttle and check all vacuum pipes.

 

[ALC]

hi again, 1st thanks for all the replies.
i'm down in Bournemouth, dorset.
the throttle sticking was one of the first things i checked.
i have done my best to look for air leaks including, spraying a bit of carb cleaner around where i couldnt reach, to see if it coughs...not a thing.
New leads, new coil packs, new main loom, new plugs, spare new maf.
thing thats pretty much what i have covered so far.
Im gonna take a look at car in the light tomorrow and see if i can spot any of your suggestions,
thx
AL

 

[Smiley]

Is the new MAF genuine MB or a cheap one?

 

[Druk]

kth286 is correct in saying the pic shows the purge valve. It might be on the N/S inner wing on a 280 just below the suspension turret top. I would investigate this further cos it shouldn't be blocked with a bolt.
The airpump on these engines is that large belt driven lump down by the alternator. It's job is to pump air into the exhaust when the engine is cold to assist the cat to reach running temp quicker. You should hear it running from a cold start then it should cut out after a few minutes idling.

Just a stab in the dark here but there is a fuel pressure reg on the end of the injector pressure rail. The diaphram in there can give idling trouble.

 

[Dieselman]

Connect a vacuum gauge to a direct manifold takeoff and see what you get. Various issues can be checked with a Vac gauge, in particular any leakage.

 

[ALC]

hi guys
hope your all having a good christmas..
does anyone happen to know anywhere in the south i can go to for a proper diagnostics at all plz ? i dont mind a bit of a drive.
Other than the last couple of replies, that i have to take a peek at, i cant yet play with anything cos it will be just my luck to kill it, and i cant chance that till after xmas period.
So the post is still open, i just wanted to be polite and make it look like i wasnt using this, since im not able to do much atm.

Enjoy the rest of the break , and again thanks for the suggestion and info.

AL

Refresher :
Intermittent hunting, sometimes light, sometimes really heavy to the point of stall.
general engine runs really well, but a very slight lumpyness to tickover can be noticed.

 

[Ian B Walker]

Ollie (Blackc55) in Portsmouth is not that far away from you (says im from ooop narth). Might be worth your while to give him a call.

 

[ALC]

hi again,
just a long shot, but is anyone aware if a thermostat is faulty it could contribute to intermittent hunting or tickover issues ?
Only reason im asking is i noticed yesterday that with my heater settings on as low as possible, just before the click to cold, hot air was intermittently being chucked through, and i also had ticker over problems for the 1st time yesterday in a few days.
Any idea guys ?