Brought my car to get it inspected 3 weeks ago for inspection and the dipshit inspector could hardly drive stick (revving the living **** outta the car just to pull it onto the dyno) and also had the car turned off for about 15-20 minutes before he conducted the test... In any case he had the car boosting through most of the acceleration part of the dyno test. Of course the car failed:

Emission Reading Limit
HC grams per mile 02.71 1.20
CO grams per mile 030.20 020.00
NOx grams per mile 02.18 02.50

But it didn't fail by much, so I figure I'd do a couple of quick things to try to get emissions down a tad. I replaced the O2 Sensor (has been reading, through an A/F meter, leaner and the car's been backfiring more often recently, A/F meter reads richer now), spark plugs, changed the oil/filter, cleaned the K&N air filter, and drove the car pretty hard to the inspection station today (multiple runs up to redline). Unfortunately, I had to bring the car to the same shop as to not spend an extra $39 (same inspector again couldn't drive stick, let the car sit turned off for between 10-15 minutes prior to the test, and had the car boosting through the acceleration part of the test) and it failed again:

Emission Reading Limit
HC grams per mile 01.97 1.20
CO grams per mile 026.14 020.00
NOx grams per mile 01.55 02.50

I'm pretty sure that part of the problem is that the inspector had the car sit turned off prior to the test and the fact that he had the car boosting through the test, but there was one thing that kinda didn't completely jive, and I woulda missed it if I hadn't walked into the testing bay (which is supposed to be a no-no) right after the test was done. Right after the test, the testing "computer" said that the exhaust probe had "overheated" on the screen. I checked the car and the exhaust overheat light was not on in the car.

So my question is, is there a possibility that the cat in my car is either bad or going bad? I know that FD's cat is supposed to get pretty hot in order to work properly. Could it be that the cat is not getting hot enough to work properly and therefore letting the bad emissions (and very hot exhaust) through to the tailpipe therefore overheating the probe? I know the cat is not clogged because I don't have any boost problems, but has anyone had a cat gone "bad" otherwise where it just wouldn't clean up the exhaust?

Thanks!

 

Search on passing emmsions Ive heard of throwing alcohol to xylene, and yes boosting is a no no , makes the maps throw gas in like crazy.

 

Shutting the car off is also not a good thing. In Ohio you thoroughly warm it up and they keep it running until after the test is finished. If the cats are not hot, it's difficult to pass.

 

So is the high exhaust temps coming out the tailpipe OK???

Thanks!

 

The cats, themselves, generate a lot of heat oxidizing the rich (normal) fuel mixture, so the answer is yes.

 

Check your water temp sensor.. My was phucked up and made me fail.

 

How did the water temp sensor make you fail. I think mine is OK, I've also got an Autometer water temp gauge (w/sensor tapped) which is reading within range (180-210F in normal driving, read 220F after the test)...

My main concern is that the exhaust got hot enough through the catback that it caused the emissions probe they were using to "overheat". I know that the cat is supposed to get really hot, in order to filter out the "bad" emissions, but what I was wondering is the hot exhaust coming out of the tailpipe mean that the cat was not getting hot enough letting more emissions get through?

 

A bad sensor could cause the fuel mixture to be too rich. Hotter temps at the tailpipe might also indicate that the mixture is too rich. This rich mixture will go into the cats, causing them to oxidize more HC's, generate more heat, and raising the cat and tailpipe temps further than normal. Apparently, not all of the HC's are being oxidized in the cats.

Another thing that will cause excess HC's, etc., is a lack of air injection to the cat due to a bad air pump, etc., but this should make the tailpipe exhaust temperatures lower, not higher, since less stuff is getting burned.

Bad (coated, not necessarily clogged or collapsed) cats will cause excess HC's, etc., but should also result in lower tailpipe temps.

 

OK, I figured the cat was over 10 years old so it probably shoud be replaced at some point, so I went ahead and picked a low mileage (6k) stock one from a local guy whose setup his FD for racing only. Probably a good thing I did replace the cat as lots of cat innards fell out from the DP side after I removed the old one.

Went in for a "challenge" re-test, set up by the Registry here at one of their "preferred" inspection stations, where they absolutely guaranteed that the tester would know how to drive a standard. Unfortunately the testers again had to do the safety test before the emissions test, so the car sat for 15 minutes off before the test. And during the test, the tester shifted the car into 4th gear (at 30mph)?!?!?!

So while the new cat helped a bunch, I still failed with the following number:

On the graphs, there appears to be a huge jump in CO when the car was shifted into 4th gear probably at about 20 or so mph, obviously putting more load on the engine than if he left it in 3rd.

WTF? Where in the world can I find an inspection station here in MA where they actually know how to drive? Feel like taking a baseball bat with me the next time I get tested so I can smash the computer after I fail again!

 

you should turn your boost down and try adding a gallon of denatured alcohol to about 10 gallons of 93/92 octane gas. that should help get your CO down just enough to get you to pass, and as soon as the test is over, go fill up your tank with 93/92 octane gas, but don't drive hard until you empty that tank and need to fill up again. but be sure you turn the boost down.