Uneven idle, high HC (on emissions test) Please HELP!!!
Thread Starter
Member
Joined: Jan 2007
Posts: 76
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From: UK
W124 280E and a Mini R50
Uneven idle, high HC (on emissions test) Please HELP!!!
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!!!!
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!!!!
MBWorld Fanatic!
Joined: Apr 2005
Posts: 2,849
Likes: 3
From: Long Beach, Ca
lots of cars
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...
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...
Thread Starter
Member
Joined: Jan 2007
Posts: 76
Likes: 0
From: UK
W124 280E and a Mini R50
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?
MBWorld Fanatic!
Joined: Apr 2005
Posts: 2,849
Likes: 3
From: Long Beach, Ca
lots of cars
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.
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.
Thread Starter
Member
Joined: Jan 2007
Posts: 76
Likes: 0
From: UK
W124 280E and a Mini R50
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?
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?
Last edited by w124uk; Mar 18, 2007 at 03:48 AM.
Thread Starter
Member
Joined: Jan 2007
Posts: 76
Likes: 0
From: UK
W124 280E and a Mini R50
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???
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???
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MBWorld Fanatic!
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From: Bellevue, NE
1995 E320 SE, 162,000 Miles (Sold) 2007 CLK350 Cabriolet 2014 ML550
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.
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Thread Starter
Member
Joined: Jan 2007
Posts: 76
Likes: 0
From: UK
W124 280E and a Mini R50
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!
