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Discussion Starter · #1 · (Edited)
90 Celica, high HC + NOx emissions - result graphs included!! - test your knowledge

For my third time failing in a row, I have finally solved my high NOx problem but my HCs are just a tad over the allowable amount (240 / 194).

I have new cap, rotor, wires, and plugs. I will change the oil...

Can anybody recommend additional step or two to fix this problem? I use regular gasoline, will a higher octane help or make it worse? o2 sensor may be old, I cannot remember if I replaced it recently. catalytic converter is only 2 years old and should be fine. anything else? how about a fuel system cleaner? Will it help to / can I clean the injectors?

I have a 1.6L 4AFE, stock in the 1990 Celica. 224k miles.

thanks

(Please see my new post below, this was last year's initial posting).
 

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I am not familiar with emissions regulations in your state, but several steps may help to lower HC:
-find and fix vacuum leaks
-clean the PCV hose and passage;
- retard the ignition timing;
- put 20w50 "low ash" motor oil (you could drain it later and put the grade you normally use for the season;
if all of the above fails, the least expensive cat will make car to pass; then put yours original back and save rthe eplacement one for another test.
 

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Discussion Starter · #3 · (Edited)
High HC + NOx, see graphs for HC, CO, NOx, and CO2

Hi,

90 celica ST, 236K miles

Any comments on my NEW emissions results would be great. I have high HC (again) when engine is idle or low RPM, and this gets better with more load/higher RPM (see graphs below). I bought a new catalytic converter a year ago (for last inspection) and barely passed after that (it didn't change readings much). I believe my EGR is working fine, I've checked. My timing is, if anything, a little retarded. New Positive Crankcase Ventilation (PCV) valve. Plugs, wires, and cap will be replaced, but I had similar readings with all new ones last year. <-- same with air filter.

Should I replace O2 sensor? If I throw on a new cat it would probably help me pass again, but if I'm running lean or rich, I'd rather fix it and improve my mileage or performance.

Attached: I have scanned the readings graphs in case they can help you diagnose.

My readings (also on image):
HC - 2.0998 (1.4 GPM is limit)
CO - 13.0696 (30 is limit)
NOx - 2.5355 (2.5 is limit)

^Maryland limits



http://s301.photobucket.com/albums/nn56/baf00n/?action=view&current=Emissions.jpg

Any comments will be appreciated and will help me waste less money!

Thanks


Additional Info - for some reason my cooling fan is always running. I changed the Coolant Temp Sensor and that didn't help. My car also has a hard start when its been sitting for a while (it's worse if cooler outside). --just in case it's relevant
 

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Pull your O2 sensor and inspect and test it.

The fan is reverse-wired, so if something in the circuit fails, it will stay ON all the time to prevent overheating.
If it's not the temp sensor, then check the relays, fuses or anything else in the circuit.
 

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Discussion Starter · #5 ·
Thanks Rick,

I've been thinking about what you posted and realized that I may have been overlooking the electrical aspect of my car. I currently have 3 problems that could be electric-related:

1) Fan always running
2) Hard start (cold start injector recently replaced with no improvement)
3) EGR VSV doesn't seem to be operating

I'll have to look into the electrical aspect and check the fuses and all.

Thanks
 

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Discussion Starter · #6 ·
Which Fuse

I have a manual and can't seem to find this particular information:

Anybody know which fuse is for the EGR-VSV? How about the Coolant Temp Sensor? How about the Cold Start Injector?
 

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CRC sells a product called Guaranteed To Pass Emissions Test Formula which might help.

http://www.crcindustries.com/auto/content/prod_detail.aspx?PN=05063&S=N

I believe you are supposed to use a fuel injector cleaner every 1000 miles and fuel system cleaner every 3000 miles, but they do just want you to buy the product. At least CRC will refund the money if you don't pass.
 
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