w124uk

Hi guys.
I'm still having problams with my w124 103 engine (2.6) 1991 80K miles
The engine doesn't tick over nicely - it's uneaven and it shakes at idle. I've replaced the following:
- spark plugs
- spark (HT) leads
- distributor cap
- rotor arm
- OVP relay
- fuel filter
- air filter
- temperature sensor (the one that feeds the ECU)
- lambda (oxygen) sensor

and I've checked the following:
- engine mounts
- air leaks at the injector seals
- air leaks on the inlet manifold gasket
- vacuum hoses near the inlet manifold

Today once again I've tried to check the emissions...had to try and adjust it using the screw in the throttle body since the reading was way above the limits. Now I managed to get the CO emissions to 0.000 (limit 0.300 for a car with a cat) but the HC is way over the limit (about 1.000 instead of 0.200) so looks like there's plenty of unburnt fuel...is that correct?

All the Mercedes specialists give up as soon as I describe the problem...they're scared to death of those old mercs...

So what should I do next? Do you think it's a faulty fuel metering head or faulty ECU? I'm just about to give up and buy both hoping it'll cure the problem

HELP!!!!

YNVDIZW124

You can have more than one problem if it's not idling right....Also remember when you lean out the mixture your Hydro carbons can go up...

Re-adjust the mixture on the idle screw till it's around .150 if you can

I would check or replace the EHA valve next to the fuel distributor and clean the idle control valve...

w124uk

I've not checked the mixture after I've replaced the temperature sensor - I want to do it Sunday morning before work. I've noticed that the car no longer takes ages to start - it used to take about 7s of cranking.

I've cleaned the ICV a while ago and it works fine.
And what's an EHA valve? Do you mean the air mass meter?

My other guess is it might be a very slight air leak on the joint between the air mass meter and the fuel distributor (I used a couple of cans of brake cleaner and the revvs did go up a bit when I sprayed it around that joint. I need to order that rubber seal and check it out...

Do you think I shound replace the injectors as well?

YNVDIZW124

Injectors should be fine but if the rubber seals on top are hard then they might leak. The EHA is on the side of the fuel distributor and controls the fuel mixture also replace the O ring under the fuel distributor and check the rubber hoses that go to and from the ICV. Also i would let the car warm up until the aux fans turn on and give it a couple good revs to blow the junk out the cat.

My car passes 2 years ago this way and i have to do the smog test on monday so i'll keep you posted. I also changed the O2 sensor before i did the smog with a cheap one from a 1990 mustang.

w124uk

I'm not bothered about the smog test - since my car is from 1991 it only passes a non-cat smog test here so the results are in norm for the non-cat cars. The thing that annoys me is the uneven tickover...
I've checked the injector seals - no matter how much brake cleaner I spray around the injector seals, the revvs stay the same. They raise a bit only when I spray it near the fuel metering head / air mass meter joint.

I bought a brand new NGK lambda sond - couldn't be bothered to look for a generic one and play with wires. It wasn't expensive neither - only about $100 or so.

So what does EHA stand for? Is that the black thing in the pic?

shdoug

EHA- Electrohydraulic Actuator; yes that's it in the pic.

w124uk

I've resealed the connection between the air mass meter and the fuel distributor. Just checked the emissions again. The car still shakes at idle but the emissions are perfect. Ill list them below, limits in bracket for cars registered after 1994 = the most restrictive:

fast idle (2500-3000rpm)
CO % vol 0.025 (0.300)
HC ppm vol 14 (200)
lambda 1.012 (0.970-1. 030)
CO2 % vol 14.76 (not required for test)
O2 %vol 0.27 (not required for test)

normal idle (450-1500rpm)
CO % vol 0.017 (0.500)
HC ppm vol 14 (not required for test)
lambda 1.007 (not required for test)
CO2 % vol 14.77 (not required for test)
O2 %vol 0.27 (not required for test)


So now I'm even more confused.... Any ideas guys???

shdoug

How did you check the engine mounts? Mine looked fine but the car felt like a jackhammer at a stoplight. The one by the exhaust manifold gets broken down by the heat. If it's original, I would bet anything it's shot.

w124uk

Just tried the good old method - revved the engine very hard when it was ticking over. With all cars I came across that had damaged engine mounts, the engine felt like it wanted to drop off the car ;-) not on this w124. It just revved hard (5-6K rpm) but it felt OK.

So are the mounts very particular on the w124? How should I check them? When the engine ticks over it just shakes, there is no regular missfire or anything... I just want to fix it!

w124uk

Looks like it might be the EHA - I've just checked and when I disconnected the EHA wire there was no difference at all...
what do you think?