1989 190E 2.6L Gas/Auto Trans.

Failed Emission Test:

Low Speed Test Failures:

1)Hydrocarbons HC (ppm) 185 my car (162 limit)
2)Nox (ppm) 2139 my car (1227 limit)

High Speed Failures:

1)Nox (ppm) 1664 my car (1121 limit)

The vehicle has 195K on it, the engine was just dropped in from an 84K car, it has splendid compression at 180-190psi per cylinder.
I am almost sure that Nox failure is indicative of EGR problem. I dont know anything about Mercedes EGR system. What could cause HC to fail, only at low speed? The HC passed by 10 ppm on the high speed test.

Any ideas? I am selling this car and the interested buyer wont buy unless it passes. The emission tech said the idle was too high, about 1500 rpms. Is this adjustable? How?

Prevost3000

I would scan for similar posts here that contain feedback by a member named Duke2.6.

His findings indicate that 103 motors have a tendency to produce high numbers, but they are manageable. From what I've read here, your NOx reading might be traced by to the EGR system. That's certainly worth looking at.

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Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

The cats are extremely important on the M103s. Some times the tech doesn't heat them up enough. You also have a problem in the Idle Air Management System causing the 1500 rpm idle.

__________________
Auto Zentral Ltd.

I am checking the O2 sensor now. It is at 100C, its about 80 ambient. I get a fluxuation from 0.01 to 0.7. The flux is pretty rapid, my meter almost cant keep up. I shaved some insulation off the sensor side of the black/green connector and hooked my neg lead to batt ground. Is this normal? I dont know. another site said .2 to .8.

I get 9.5 volts roughly when checking at pins 2 & 3 of the round diagnostic connector X11. If i unplug the O2 it drops to around 6 VDC. Is this normal?

I am failing HC at idle. I have new H9DC plugs and my compression is 180-190psi.

I found out that the M103 engine doesnt have an EGR, its all Cats. I dont think it was hot enough at the first smog test. I heard a site say 50mph for 7 minutes. I put a whole tank of 91 octane and a bottle of RXP in the tank and I will try it when the tank is nearly empty, i will rev the engine in gear while waiting for the test.

Does anyone have any experience with adjusting the hex screw on the air cleaner? Please indulge. I am listening.

Last minute edit: The idle is around 1500-2000. I unplugged the IAC (idle air controller) and it went down to 700. I have 12.97 volts at the 2 pin plug at the IAC. The a/c is off or on, the volts do not vary. The car is up to 100C.
Any clues?

Prevost3000