Failed Emission Test TX
 

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.

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.

A Quick Update:
 

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