I carried my recently purchased 90 300e for an emissions check today. Unfortunately,it didn't pass the Hydrocarbons portion of the test, with a reading of 215 vs an allowable of 137, everything else seems to be fine. The car has 111k miles. Any ideas on what might cause this type problem? Thanks in advance for your insight.

Ken Yancey

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1987 300SDL
1990 300E
1989 300E
1986 300E
1981 300D
1983 240D

What was the CO reading? I would think you could adjust some of it out, but you should have the car reallly hot to test if they don't use a dyno. IF they do use a dyno and test for the NOx, you will need the engine hot, but not overly hot, this will cause more NOx.

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Benzmac:
Donnie Drummonds
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS

Banzmac,
Thanks for your quick response. Here are the rest of the readings:

--------Result----Allowable-------
CO-% = .17 Vs .87
NO-ppm = 53 Vs 956
CO+CO2%= 14.6 Vs 6.0 min.

Also, I had drove the car for about 15 minutes before it was tested.

Ken Yancey

[Edited by bigbenzman on 12-28-2000 at 08:53 PM]

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1987 300SDL
1990 300E
1989 300E
1986 300E
1981 300D
1983 240D

High HC is a result of misfire (unburnt fuel). I would start with secondary ignition, cap, rotor, wires, plugs, coil, & OR vacuum leak in the intake area. How old is the O2 sensor?? What was the last time engine tune(secondary ign.) was checked? If new plugs are needed don't forget to check compression!

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MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

I recently had the same problem with my '86 420SEL. It was 196 on the hydrocarbons (passed everything else no problem) against an allowable 102 (Ontario Canada). They adjusted the lambda (I think that means new 02 sensor) and that brought it down to 160. Then they did a motor vac and had me drive it really hard for a few days to clean it out. It tested the third time at 101 against 102. That was good enough for me. (also had new plugs put in). I have a bit of a rough idle (not related to secondary igintion as that is all brand new) that I think is one or two cylinders running rich due to worn injector plungers. Have Benzmac's suggestions checked out. Also it is a good idea to have your engine good and hot for these tests as that usually helps. I would sayu drive it for an hour on the highway and then have it tested immediately.

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Jason Priest
1999 E430
1995 E420 - retired
1986 420SEL - retired