OK, here in GA they test it at idle and under load. One is called the "25/25 Test" and the other one is called the "50/15 Test." Everything on the "50/15 Test" passed, however on the "25/25 Test" I failed on HC's and NO's.

HC - ppm Reading: 137 Allowable: 117

NO - ppm Reading: 1387 Allowable: 821

Now while in line, I had the A/C on full blast and got the car up to 220*, however after searching around on the boards, apparently by allowing the car to get really hot I can send my NO through the roof. . . is that true? How do I fix the rest of this?

I told the guy it was an LO3, but really I'm running an LO5 with Trick Flow heads and a mild cam and full exhaust. All smog and emissions equipment is intact. The chip was tuned a week ago on the dyno so the A/F ratio is spot on, maybe just a hair on the rich side.

 

"Slightly rich" will cause your HC problem.

Too hot can cause NOx problems. The nitrogen oxide compounds are formed in high pressure/high temperature conditions. The EGR is there to cool down the combustion temps to reduce the NOx formation.

 

Are the limits the same,since there is a difference in displacement?

 

Well I'm only 20 over on the HC's on the one test. However, I would imagine the NO's are high given the temp I let it get it seeing how it was fine under the 15 mph test.

What affect would a bad catalytic converter have?
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Well in GA, you can only switch motors to something that was offered in the car at the time (per the test guy). So I could say it was a 350 TPI but I'm not sure of any new parameters it would set. The guy said he can't tell of any correlation between engine size and amout allowed. He says sometimes little 4cyl Toyota trucks have more room than a 4.3L S-10 . . . so I really don't know.

 

So is it the idle test you failed on? I would back the timing down a bunch to get a more complete burn. I failed the idle portion of my test with the timing @ 8* (TPI) motor and no egr or air pump on the car. Backed it down to 0* and popped in a new 02 sensor and all the readings dropped by almost half!

 

Yeah, sorry I didn't explain the test lingo:

50/15 = 50 seconds @ 15 mph

25/25 = 25 seconds @ 25 mph

I went and talked to a trusted mechanic who's done alot of work on the car and he recommend first chucking the Bosch O2 sensor for an AC Delco one and to do a vacuum test on the EGR valve. He said if those two things don't fix it, then he would suggest dropping the money on a catalytic converter.

I really don't want to have to play with the tune seeing how I just got it to where I want it to be.

 

I did the same....gassed the bosch for an ac 02. If you back down the timing you won't effect the prom. Just test it and set it back where you had it! Thats all I did.....took me all of about 20 minutes!

 

Yeah, I did that last year.

 

In case you were wondering, I deleted the posts with inappropriate material.

 

But...but..but....they were so relevant to the origional question! Jeez.....

 

Thank you.

 

Well I backed the timing off from 4* to 0* and it brought everything down, but I still failed the same two categories, only by less. On HC's I was only 5 over the allowable 117. On the NO's though I didn't make much of a dent.

I've got a new heated, AC Delco O2 coming and I'll also replace the EGR as well. Maybe that will get me to where I need to be. ???? This crap sucks.

 

High HC may mean you're too rich or burning oil. It could also mean a bad cat.

High NOx is usually an EGR issue.

New cat, new O2, new EGR valve. Be sure the cat is nice and hot prior to the test. If the cat is cold, you will fail for sure.

 

Yea it looks like you could use a catylismic convertor. Try pouring some Sea Foam in the intake and crank it over a few times while the car is off and then starting it up after about an hour, I know it sounds ghetto but it really cleans all the carbon out of the system.