Failed emission test on 87 MB 190E 8V! Help please!
 

hi! everyone! I failed the emission test on the 87 MB 190E 8V.

The result is on driving test (40km/h)

HC (ppm) Max allowable: 212 My car: 174 Ave Reading: 83 Pass

CO (%) Max allowable: 1.50 My car: 0.14 Ave Reading: 0.13 Pass

NOx (ppm) Max allowbable: 2186 My car: 223 Ave Reading: 544.50 Pass

The driving test is all passed on my car

Idle test:

HC (ppm) Max allowable: 310 My car:628 Ave Reading: 48 Fail

CO (%) Max allowable: 3.63 My car: 1.71 Ave Reading 0.07 Pass

Now, I have a question that is how do I lower down the HC in idle test.

My car's idle is little rough in the cold engine (about 700rpm to 850 rpm moving). After warm up, no problem on the idle.

I don't think so that my car has heavy vaccum leaking. Please help

Either the fuel mixture is TOO rich or the engine wasn't warm enough when the test was done.

the engine temp should be fully hot. I drove over 20 mins to test center and wait over 15 min there. The temp gauge is over 100 degree.

How can I adjust fuel mixture?

Do I need any new oxygen sensor, fuel injectors or anything?????

One more thing, I put the new OVP, idle control valve and fuel pressure regulator about 4 months ago due to stall idle problem.

Thanks

I wouldn't think a rich mixture would result in a pass in CO, but could be from leaky valve stem seals or worn guides?

Steve

I changed valve stem seals about 4 months ago as well.

Your engine appears to be running rich at idle, but okay under load. You need to check the EHA duty cycle using a DVM with a duty cycle function, and adjust it if it's not in the acceptable range. A scope can also be used to look at the O2 sensor output. Look at:

www.landiss.com/mixture.htm

Duke

reset your fuel mixture. just did mine last week.
do the mix first, if it does not stay , then go on and check your o2 sensor.
my mixture was just like yours, only had to turn the adjuster bout one eighth counter clock wise
you should have the smog shop reset the mixture to get it right. if you lean it a little to much and your nox will fail.
i work as a smog tech so i do have some experiance on this
good luck
rich, from quebec