Took my 92 Tercel to a Test Only station and I failed to the levels of a gross polluter.

15mph:
HC:
MAX: 114 Meas: 243

NOx:
Max 273 Meas: 2563

25mph:
HC:
Max: 82 Meas: 48

NOx:
Max: 812 Meas:1498


I found out that the secondary valve for the EGR was broken. I replaced that, I also found that the back-pressure port on the EGR was clogged. I fixed these issues.
My timing was at 12 deg so I backed it down to 8deg. Normal is 10 deg.
I checked the o2 sensor voltage. it fluctuated normally and didn't stick high or low. My cat has only about 1,000 miles on it, maybe 2,000.

I brought my car to my friend's non test only smog shop and we put the car on the dyno in diagnostic mode. It passes if we get it hot.

I drove the car to hell and back nice and toasty and brought it to the Test Only guy. I was able to immediately get the car on the dyno.

I failed again:

15mph
HC:
Max: 114 Meas: 216

NOx:
Max: 873 Meas: 961

25mph
HC:
Max: 82 Meas: 81

NOx:
Max: 812 Meas: 615


So the numbers got better, but still a fail. I find it hard to believe that my cat has failed. The o2 sensor is the original and I'm not sure how accurate a voltmeter test is so I'm posting these numbers to get an idea on what to do from here.

 

Gotta love Tercels. I have a 95 for a daily beater and I had a 92 several years ago.

 

I removed the passenger seat and haul around parts with the thing.

Ok I checked the plugs, they are white so the thing is running lean.
I got a new o2 just to be on the safe side and I'm going to pick up a new fuel filter in the morning. I also dumped a bottle of sea foam in the tank to clean up the injectors.

I knew the damn thing ran lean, I was just getting a lapse of judgment because I just got used to the fact that it did, and I was hungry. I also had to run 91 octane in it just to keep it from pinging. I think if I fix this lean issue I can go back to running 87, which will work better with this low compression engine.

 

dilute the fuel down about 15% with denatured alcohol.

 

when was the last time you changed the oil?

 

the high nox also suggest to me that it has alot of internal buildup on the pistons, the injectors probably could also stand to be serviced. something is telling the ECU that the engine needs more fuel than it needs so start with the basics and check the AFM/MAF/MAP sensor and connections, check for vacuum leaks, clean the throttle body with carb cleaner, change the air filter, fuel filter and spark plugs and go from there. basic tune up crap.

 

basic tune up was handled, along with inspection and cleaning stuff. Thats the first thing I do before a smog.
Replaced the fuel filter today, mud came out of the old one. it was clogged for sure.
I also checked the voltage on the o2 sensor at idle. It flutters between .4 and .6 so that would tell me that it is running stoich at idle at least.

I took it around the block and checked the plugs again... they are showing lean still. makes me want to put my wideband in the car for testing. Next step for me is to do a real injector cleaning. Either that or do that alcohol trick and check it on my friend's dyno.

 

if the O2 sensor is accurate then it is only running rich under a load which would mean a MAF/AFM issue or a leak in the system somewhere.

 

Just referring the new members bro! I'm glad you're helping everyone out!

 

******* ROFL

 

 

Took it back to my friends dyno and it again will pass if it gets loaded up before running the test. The numbers are actually quite well within the range too. So at this point the cat just seems a bit weak. The guy that was doing my test would only hold the throttle for 2 mins and never give it a load before starting the test. Gonna just get a new cat and find a guy that will load it up first.

 

Make sure the car is warmed up too.

 

OR just junk it. that will save you lots of $$$ and headache.

 

back up

 

Thanks for clearing things up in the other thread, Alex. You can delete the other one if you want to.

Ok for those who are curious. I put in a new cat and the numbers changed drastically:
15mph:
HC: 18 NOx:10

25mph:
HC: 11 NOx:8

I assume the other cat got fried because I ran it lean for so long.

 

k no problem bro

 

i wish i had seen this thread earlier.
if your nox are high, lean yes
if your hc are high, rich yes
both at the same time? either you are having a massive lean misfire, or the cat is to be called into question.
glad to see you fixed it, get it richened up a bit though, dont want to destroy another cat
you never posted 02 and co2 readings

Lloyd