help ... failed my e test....

[RandyBee]

40 km/h
limit reading result
HC ppm 58 6 PASS
CO % 0.32 .00 Pass
NO ppm 0435 854 Fail


every thing on curb idle passed this is a 1993 grand prix 143000km

they said could be the egr valve what should i do ? so i removed and cleaned it . it was not all that bad will try to run guaranteed to pass and try again now can i unplug the egr valve for the E-test to pass or will this make it worse. and i was also told to burn 3litres of methal hydrate then take for test yes or no

[Sonbuster]

new cat?

[ES_Revenge]

new cat?

Seems to be the cure-all for emissions failures eh? However in this case, it looks like the catalytic converter is working fine. The cat in modern cars is a "3-way catalyst" meaning he almost certainly would not have such low numbers on the other two emissions with a bad cat.

The methanol burning idea is a funny one. It works but not in all cases (though it sounds like it would for you) but careful becuase you might damage injectors or cause other problems from doing it. A few litres shouldn't hurt anything too badly and if you gas up right after (to dilute it) then you might be okay.

You cannot unplug the EGR because that will set off an emissions-related code and you'll fail automatically. The only way to do that would be to have something emulate the EGR (electrically) to the ECM so it thinks it's there, while in reality it is disconnected. However that's going to be more trouble than actually just fixing the problem correctly, lol.

Are you only failing the NO on the 40km/h test and passing everything on the idle test?

[RandyBee]

Seems to be the cure-all for emissions failures eh? However in this case, it looks like the catalytic converter is working fine. The cat in modern cars is a "3-way catalyst" meaning he almost certainly would not have such low numbers on the other two emissions with a bad cat.

The methanol burning idea is a funny one. It works but not in all cases (though it sounds like it would for you) but careful becuase you might damage injectors or cause other problems from doing it. A few litres shouldn't hurt anything too badly and if you gas up right after (to dilute it) then you might be okay.

You cannot unplug the EGR because that will set off an emissions-related code and you'll fail automatically. The only way to do that would be to have something emulate the EGR (electrically) to the ECM so it thinks it's there, while in reality it is disconnected. However that's going to be more trouble than actually just fixing the problem correctly, lol.

Are you only failing the NO on the 40km/h test and passing everything on the idle test?

yes i pass all others at curb idle i also put high octane fuel in for the e-test now they tell this is not good so im on the right track then and yes the cat is just fine the low scores prove that

[DragonZealot]

Disconnecting the EGR will cause it to close all the time and thus making more NOx due to lack of circulation.

Emission test does not check NOx at idle so the cat is still in the possibility list although it is low in the list.

EGR blockage is one possibility which can be corrected by cleaning but blockage build up gradually overtime. If NOx was very low last time and now it jumped sky high it is probably not because of blockage.

It is more important to check the correction operation of the EGR, ie, make sure it opens at part thorttle. This would confirm that the valve actually opens and there is vacumn driving the EGR valve.

[RandyBee]

Disconnecting the EGR will cause it to close all the time and thus making more NOx due to lack of circulation.

Emission test does not check NOx at idle so the cat is still in the possibility list although it is low in the list.

EGR blockage is one possibility which can be corrected by cleaning but blockage build up gradually overtime. If NOx was very low last time and now it jumped sky high it is probably not because of blockage.

It is more important to check the correction operation of the EGR, ie, make sure it opens at part thorttle. This would confirm that the valve actually opens and there is vacumn driving the EGR valve.

ok this is electric egr no vacumn so how do i check it to see if it is working
yes the results last time were low and now high so if not blockage then what

[DragonZealot]

ok this is electric egr no vacumn so how do i check it to see if it is working
yes the results last time were low and now high so if not blockage then what

For my car I can actually feel the valve moving while I apply gas.

For your car since it is a digital EGR you need a scan tool to command the EGR to open and then see if the engine runs rough/stall. All GM dealers and most larger shops should have the scan tool.

It is a delima since the car is 14 year old and probably does not worth a lot.