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