What is good to be done before the Emission Test?
Does it help to change oil before the Test? Any treatment solutions?
Does 260E have the water/fuel separator?
Thanks.
Andrew.

http://www.ebop.govt.nz/Air/Quality/Vehicles/Reducing-Vehicle-Emissions.asp
Petrol Vehicle Maintenance Tips
Excessive exhaust smoke can indicate engine problems. Here are some useful tips to keep your vehicle well maintained:
Change the engine oil at least as often as recommended by the vehicle manufacturer. Dirty engine oil becomes very thick and will cause excessive engine and turbocharger wear leading to increased smoke emissions.
Maintain the engine’s fuel system, as recommended by the manufacturer. This includes:
following recommended fuel filter change intervals
regularly draining the water/fuel separator
having injectors or carburettor checked and cleaned to prevent plugging and replacing them when worn
having the fuel injection pump maintained as needed.
Maintain the engine (including pistons and rings) to prevent the engine burning oil.
An exhaust emission test is an easy way of checking whether your car is meeting recommended exhaust emission standards. A qualified mechanic can advise you how emissions from your vehicle can be reduced.

I always thought a clean air filter was very important. If you can, check the egr valve and pcv valve to make sure they're not acting funny. 10% ethanol gas may help. Make sure the check engine light works and is not lit after starting the car.

Make sure the car is completely warmed up before testing. Don't let the inspector make you wait in line for any length of time, since the engine can cool off during that time.

__________________
95 E320 Cabriolet, 159K

Thanks Kestas,
How to check the egr valve and pcv valve to make sure they're not acting funny?
Which gas has 10% ethanol ?

They say a pcv valve should have a nice metallic "clink" sound, though I've also heard it can still work otherwise. My engine doesn't have a pcv valve, so your's may not either.

There is a simple egr check where you apply vacuum to the diapragm and check for valve shaft movement to make sure it opens. A valve that doesn't close properly may give idle problems. A thorough check is more involved.

You don't state where you're from, but in some regions exclusively use 10% ethanol gas. By law, in Michigan it must be stated on the pump when 10% ethanol gas is dispensed instead of pure gasoline. We have both kinds where I live.

__________________
95 E320 Cabriolet, 159K

Or you can forget all that stuff and buy a $5.00 can of "Guaranteed to Pass".

Deanyel,

1990 300E

This $ 5.o additive you mentioned, do you think it may cause starting problem? I am not sure, but after adding this liquid and using 1/4 tank, today I can't start the car. I was thinking to take my car this weekend for the test

if your state checks for nox, then use the highest octane fuel you can find. maybe even an octane booster.
cooling system should be full.
not sure if this works but getting your car done at the coolest part of the day seems to get better numbers.
on those super hot days, maybe wait till the next morning.
also have your gas cap checked a second time if it fails the test.
clean oil does help and so does luck. car must be warmed up by driving at freeway speeds and drop it down a gear to spin the motor a little faster
good luck
rich

__________________
88 300E White, sold 9-04
88 190E Black 2.3 sold
90 300CE White, Grey sold 12-24-04
92 400E White,Grey Sold 5-06
90 300CE 91K Signal Red,Black Sold 2007
1989 300CE Smoke silver,Tan Sold 1-08
1993 300E 3.2 M104 motor
1991 300CE White,Grey
1994 E420 beautiful car,gone to new home
1994 E320 Smoke an Parchment.Beautiful car

As others have said, getting the cat fully warmed is key.

In my experience, the O2 sensor has been a top culprit for bad scores on injected cars.

I have also found significantly different results from one testing station to the next, FWIW.

Once got a bad score when I KNEW the motor was in top shape. I had recently done a substantial rebuild, and gone over everything. Went up the street, and got an excellent score.
The state recently launched an investigation into the accuracy of the tests.

__________________
1986 300E 5-Speed 240k mi.

M103s do not have a valve as part of the PCV system.

If the engine is well maintained and appears and feels to be in good working order, there are no specific actions that you need to take before the test.

These engines are very sensitive to temperature. CA has tagged them as "high emitter profile." Long periods of idle cause the converter to cool off and lose oxidation efficiency, which can cause excess HC.

In most of CA we have a two speed loaded dynomometer test called "acceleration simulation mode" or ASM. My suggestion to all is to thoroughly warm up the engine with at least 20 minutes of driving, preferably with a freeway jaunt. Go to a drivethrough place with a short line, and keep the engine at 2000-2500 until the tech is ready to take the car.

As part of the CA procedure there is a "tire dry procedure" that is used on wet days. The tech runs the engine at about 2000 on the rollers with no load for about a minute, and this will heat up the converter, so testing on a rainy day and requesting that the tech run the tire dry test will usually keep HC below the limit, though rainy days are rare for most of the year.

If you have a failure, post the type of test and all the measured gas quantities including O2 and we'll help you diagnose the problem.

Duke

I would strongly disagree about adding anything to the gas tank, octane booster will increase HC (duh) especially if the vehicle is not performing correctly, and if 'repairs' are done FIRST, then a car fails, how does one know that the ' repairs' didnt make the problem worst so now, he/she has to go and undo what they did.

I suggest only haveing the cat good and hot, meaning car at op. temp. and 1/2 tank of regular.

This is what I do, QA emissions testing and equipment.

PS. My 87 300E passed very, very clean, so dont believe folks who say " certain cars wont pass the test" its all about maintenance.

What type of test and what are the most recent numbers? What, if any, "conditioning" was applied prior to running the test?

The California Bureau of Automotive Repair, the state agency that oversees emission testing, has tagged the M103 as a "high emitter profile", and indeed, most of the test results I've seen on these engines show high HC on the first ASM test, which is run at 15 MPH under relatively high load. The second test, 25 MPH at relatively lower load usually shows signficantly lower HC and lower O2 content, indicating greater oxidation efficiency in catalyst.

My theory is that the catalyst bed cools down and I have used an IR gun to measure the surface temperature of the catalyst inlet after five to ten minutes of idling, and it drops to as little as 300F.

I maintain my car rigorously - duty cycle is right on the money, O2 sensor output is nominal, new plugs, cap and rotor, and I'm still at the ragged edge if I don't take specific action to ensure that the converter is hot, such as holding higher than idle revs prior to the test or going on a rainy day and asking them to run the "tire dry test".

It just seems to be the nature of the M103 beast that the emissions are high unless specific steps are taken to keep the catalyst as hot as possible. It's too bad the initial timing cannot be adjusted on these engines as retarding it five or so degrees from the set nine degrees would probably increase the EGT enough to keep the converter sufficienctly hot to oxidize efficiently for the entire duration of the test, which would yield a lower HC reading at 15 MPH rather than being on the ragged edge or marginally failing.


Duke