Failed Emission Test...

[TRENT]

Help!
I have a 94 lt1 6 spd with 70k on it and when I went for my emission test it failed! The HC were low as were the CO% the NO ppm was over 737 and 484 is a pass. The Tech diagnosed that the EGR was operative but that there was no signal (ground) from the ECM and that the only way to repair this was to replace the entire ECM with a new GM version and then have it recalibrated. Any other ideas would be greatly appreciated!
Thanks,
Trent

 

[69MyWay]

Trent,

Was the engine to full operating temp?

If not, first warm it up at home with premium fuel and any "emissions cure" additive you can find for the tank.

Drop it in low gear and flogg it out a bit on the way to testing.

Let it stay running while waiting.

Sometimes, they are just not hot enough to really kick off the cats.

Also, check to make sure your air pump is working/running. It makes a humming noise when it is spinning like a hair dryer.

 

[WhalePirot]

I agree with getting the CATs nice and hot and running good fuel.

Resetting the computer by disconnecting the power or at least ten seconds has also allowed my car to pass after a failure; twice.

Mike

 

[TRENT]

Hello and thanks for the input!
I have done some more investigating and by tapping into the ground wire which runs from the EGR solenoid to the ECM (and closes the loop, grounding the solenoid to the ECM whenever it thinks the EGR should work) and measuring the resistance between this wire and ground during test drives. I have noticed that the resistance goes from infinite to 1 ohm during certin circumstances ie: moderate load at 2000 RPM in second gear. So I now know that the ECM is in fact closing the loop and grounding the EGR solenoid on certain occasions. Does this mean the ECM is OK and maybe I just had a bad test or do you think that the program in the ECM can be tweaked to ground the EGR solenoid under different (read lighter load) conditions? Or am I out of my tree and should I just buy 10 cents worth of vacuum hose, bypass the solenoid and let the EGR work solely on the manifold vacuum and try to pass the test again. Thanks in advance for your advice!
Trent

 

[69MyWay]

Trent,

Unless you are getting a check engine light, I would just leave the computer and EGR alone.

Try what we mentioned above on a second test and see what happens.

I have a feeling when it is good and hot with good additive in the tank (emissions cure) it will pass with flying colors.

 

[RedRagTop]

Trent; Up here we don't have no stinkin' emission testing!
Do you guys down there get randomly checked while driving for this? Wondering how that works for us guys who head south once in a while, going to Wasaga Corvette Weekend in Aug and go with a couple 60's cars.
Hope we're exempt...

 

[TRENT]

Ok,
I take your advice, remove the hypertech program get the car to run super hot, buy a can of "emission test goop" follow all the instructions and show up to have the car tested this morning and the kid running the test machine says "your car has ZR1 exhaust tips and our shops exhaust evacuation system doesn't have a large rectangular piece of hose to fit over the large rectangular tail pipe opening so I cannot test your car on the Dyno WOULD IT BE OK WITH YOU IF I DROVE THE CAR INTO THE BAY FRONTWARDS, LEFT THE BAY DOOR OPEN AND TESTED YOUR CAR AT IDLE AND AT 2500 RPM AND SKIPPED THE NOx TEST?" Apparently certain vehicles (ie: all wheel drive) cannot be run on the dyno and it is up to the Air Care technician which test he is going to run and he sets the parameters as to what will be tested.. and if he decides that this particular vehicle isn't suitable to be dyno tested then he only need test at idle and at 2500 RPM and the test under load on the dyno (which is the one that was giving me the grief with high NOx readings) need not be done.... so in at nutshell I am not sure if the car would have passed the original test or not but I got my pass certificate anyway and can forget about it for 2 more years and will hope that they still don't have the proper piece of hose to fit over my tailpipes in 2005 either.

 

[TomOB]

My 1990 blue auto with 110k miles failed the test on friday. My family is thinking the guy is a little shady as we brought it into him about 2 months ago for some intensive labor on various parts, kinda like a freshner, and the guy said it would pass inspection without a fault.
I get the emissions test back, i failed on NOx, had a 3.6 gpm or something, limit is 2. went and checked last years and the limit was 4 (the CO and HC limits are down by more than 50% too). Guy tells me I need a new cat. I said, yea, ok, i need to think about it, bud. I don't know if he entered in the wrong limits or if NY state is being a pain in my ass and lowering the limits on a 13+ yr old car so significantly. They dont require a '65 to slap on cats, why would they expect a 1990 to meet new stringent rules? Checked online, last time the limit went down by 50% was in 1977.
Guy also said i had an oil leak. Checked for spots under the car and the oil level---full. All signs are pointing to a shady, shady man. I should put some zr1 tips on my car and move to canada, i guess.
BTW, this is my toyota corolla! i figured if i mentioned that upfront no one would bother reading it.....But this car is how i can afford to get a vette, when the right one comes around!

 

[yellow_2002_germany]

What I did...

when I lived in a state that required emissions tests but did not have state run testing centers was go to a place that did testing but did not do emission repairs. I figured that way they would have no vested interest if the car passed or failed. If they offer repairs and the car fails...."we can fix that!"

 

[oldace84]

Thats one of my biggest fears out here in Southeren CA....is flunking the test.....
I run the car for at least an hour on the frwy....then leave it running while I wait to get it tested....
It really sucks.......why should I fear getting it smogged...well because if I don't pass....I can't drive my baby...
tony