Help: 88 190e 2.3 failed emissions
 

196k mi

Passed 25/25 test, failed 50/15 test

NOx ppm was 2756 (allow 1323)

Oil change was done 25mi prior to test. Car has new coil, plugs, wires, rotor, cap, and O2 sensor.

Thanks in advance for any advice you guys can provide :)

Hopefully its something minor, but as a result of poor maintenance by previous owners, my 88 300E failed the idle speed emmisions test but still passed the high speed test. Mechanic determined that engine management computer was running in open loop mode (not managing engine), he fixed that but it still wouldn't pass. Service tech then pulled the valve cover and discovered badly worn cam lobes which was causing engine to emit too much bad stuff at idle speed. Result, major bills. I have heard that if a car fails the high speed test then the catalytic converters could be a potential source of the problem.
My suggestion unless you are a good benz mechanic yourself, take it to a pro for a diagnostic. A friend of mine has an 02 WRX also, sweet car.

http://www.peachparts.com/shopforum/showthread.php?threadid=46038&highlight=test

http://www.peachparts.com/shopforum/showthread.php?threadid=17187&highlight=test

http://www.peachparts.com/shopforum/showthread.php?threadid=8652&highlight=test

http://www.peachparts.com/shopforum/showthread.php?threadid=6988&highlight=test

http://www.peachparts.com/shopforum/showthread.php?threadid=16119&highlight=emission

Lots of ideas in these threads. Many point to a worn out cat.

One simple trick that might help is to first drive the car on the open road a fair distance - get it good and hot, then take it straight in to the testing facility. Try to be the first one in line.
Fully warmed up engines supposedly run a little cleaner.

This is very good advice... Many people get up in the a.m. and drive down to the local gas station to have their car inspected, The only problem here is that your cat never gets a chance to fully warm up. Cats don't begin to fully function properly until they reach around 800 - 900 degrees. Take her out for stroll to stretch her legs before hand, and call ahead to the service station, some allow appointments..... :)

Hope everything goes well......