<!-- from fixya rte -->Won't pass emissions text - 1998 Mercedes-Benz C-Class

Technical problem that needs manufacture.

If egr valve is stuck open can cause raunchy smell from exhaust, hense high readings. usually this causes rough idle though.

What is the reason that it wont pass? High levels of WHAT? What is the year and make and model? Are there any check engine light codes?

You & we need to know what it failed for

What Emission Gas & what are your State limits
& what did your vehicle read?

You can study exhaust gases on the internet & see
what area of the vehicle needs work based on the gas
readings

Have to educate yourself

Do not wait for someone to tell you things

You won't learn or remember if you don't
study on your own or don't start a binder &
take notes & copy web site info,punch the holes
& put in the binder

Then you take your info out to the car & make the
tests & fix things

Sometimes the emission light will come on if the gasket on the gas cap is worn or dirty, thus not sealing properly. If it doesn't look worn, then try cleaning it.

P0443 is for EVAP Purge Solenoid Circuit.
You can still drive it, but it'll cause emission related problems and you won't be able to pass emissions.
To replace it, it's under the hood, drivers side, near the rear corner and is shaped like a little cylinder. Fairly easy to go to a local parts store and replace yourself.

I’m happy to help further over the phone at https://www.6ya.com/expert/jason_00b31cc8f593773a

What fault code is being set?

You need a specific adapter to scan your trouble codes. Vehicles prior to 1996 use OBD1 scanners, which are very expensive. Your best bet is to call around a few shops in your area and ask what they would charge to diagnose the code. It sounds like you may have more than 1 problem. The emissions could be due to a bad oxygen sensor and acceleration problem may be due to bad plugs, plug wires, clogged fuel filter, rotor and distributor cap, etc. Do a tune up on it, then see where you stand. At least you won't have to pay a shop to do it if that fixes your acceleration problem.

You change oxygen sensors? thoses are now considered part of of tuneup on high mileage engines,plus if you drive highway for 30-49 miles before going gettting emissions testing you get better results.

IF DECELERATION FUEL REDUCTION SYSTEM IS NOT OPERATING, FUEL ECONOMY WILL BE REDUCED WHILE HC AND CO EMISSIONS ARE INCREASD.SEE ON MANY ENGINES WITH DECELERATION FUEL REDUCTION SYSTEMS THE PCM STOPS GROUNDING THE INJECTORS IN A SPECIFIC RPM, DURING DECELERATION.