93 190E 2.6 fail smog, EGR problems
 

went to smog the 190 today, and failed smog due to high nox emissions and high hc. took the car home and examined the EGR valve and i found the rubber vacuum hose to be completely ripped up. second, i applied vacuum directly on the EGR valve and the diaphragm did not hold the vacuum at all.

so it looks like I will need to replace the EGR valve itself and the vacuum lines that go with it. my question is, how do I ensure that the EGR is working when supposed to? in order words, when does the EGR valve get vacuum to open up? at partial throttle? full throttle? certain rpms?

thanks in advanced.

You can do an EGR Flow test with a hand vacuum pump.

You attach it to the egr port and pull at least 12" of vac with engine at idle and coolant at normal temp. The car should attemp to stall/run rough with egr open. If not , then you have egr tube blockage .
You also want to hear the egr Snap shut when you release the vac supply.
EGR never gets vac @ idle or full throttle.

mmk, thank you, that was the exact response i was looking for. I'll give that a try when i install the new egr valve.

here are the results of my smog test, maybe i am missing other things you guys can catch for me:

15mph @ 1474rpm:
%CO2: 14.6
%02: 0.0
HC (PPM): Max: 86, Ave: 21, Meas: 160
CO (%): Max: 0.50, Ave: 0.06, Meas: 0.16
NO (PPM): Max: 697, Ave: 150, Meas: 903

25mph @ 1423rpm:
%CO2: 14.5
%02: 0.1
HC (PPM): Max: 51, Ave: 13, Meas: 64
CO (%): Max: 0.48, Ave: 0.05, Meas: 0.04
NO (PPM): Max: 724, Ave: 136, Meas: 237

Bold results are fail

Does it make sense that my nox emissions for 25mph pass but fail at 15mph?

alright, got the new EGR valve installed. i wasnt sure if i was applying 12'' of pressure, but i opened the EGR entirely and the car ran slightly rougher. It wasnt enough to make the engine stall or anything. i also heard a PSSSSSS noise, which i assume is the exhaust gasses running through the EGR and into the intake manifold.

another little test I did after i connected all the vacuum lines back up was to open the throttle body manually and watch the EGR valve. i did see the valve open up when i pulled the linkages and drop back down when i let it idle. So i think it is working :)

hope this works out for me when i smog it again.

took the car in for smog today, and it passed!

here are the new readings

15mph @ 1460rpm:
%CO2: 12.9
%02: 1.4
HC (PPM): Max: 86, Ave: 21, Meas: 85
CO (%): Max: 0.50, Ave: 0.06, Meas: 0.0.03
NO (PPM): Max: 697, Ave: 150, Meas: 168

25mph @ 1412rpm:
%CO2: 12.7
%02: 1.8
HC (PPM): Max: 51, Ave: 13, Meas: 47
CO (%): Max: 0.48, Ave: 0.05, Meas: 0.01
NO (PPM): Max: 724, Ave: 136, Meas: 144