I have a 1990 ef, dpfi, new cat a few months ago, wires to temp sensor are shot and broke off. I am going to replace those wires and put new plugs. Car runs great no noticeable problems. I was wondering if another new cat and an o2 sensor would be necessary. I failed due to high nox but i dont know if the temp sensor issue would be my problem, also if the o2 sensor was bad wouldnt it throw a code?

 

http://www.nichols.nu/tip766.htm

run higher octane gas such as 93 or higher. check for vac leaks, change out your plugs just before your test. Check ignition timing.. possible bad cat or not HOT enough prior to test. Change 02, as our one wires tend not to throw a code if they go bad.

 

Why the hell does everyone say to run higher octane fuel? The lower the octane, the better it burns.

 

nox, emissions are from cylinder temps being to HOT.. basically a LEAN condition. Running higher octane is slower to burn and helps cool down the cylinder temps. better burning is equal to the running condition of the engine, as too hot of a burn on too low of an octane fuel creates chemical reactions that releases certain gases and in this case, higher NOX emissions. too hot of a burn and you get engine knock.

 

I smog atleast 1 or 2 cars every month, so i think i can help. For sure check your ignition timing, first connect the temp and wait for the car to conduct the warm up period once it idles back down then do the timing. Another thing i learn was the closer the cat is to the headers the better your emissions will be. I would for sure get another CAT probably from a different location, those numbers are to high for it to be just timing. I say because you mention your car runs good chance is it might just be a degree or two off but not enought for those numbers. I hate to tell you but if your car is runing fairly good you may have an ECU issue as rare as it may be. I have had that happen also if you can barrow or get one at the junk it would not be a bad idea. Another thing you have to make sure, is to have a good O2 sensor. Since you failed on NOX it will lean more towards to the cat side of things. Don't be afraid once you fix your car to see water spitting out the exaust in the morning. That is what the cat does convert the NOX fumes in to water vapor. All disconnected sensor effect the fuel map one way or another so make sure everything is connected properly. hope this helps.
try and find a center that does not charge if you do not pass. not the centers that just give you 1 free retest.

 

NOX is a cat not doing it's job...

Ok, I found my smog papers from 09-09. This is with a JDM B16, S2 IM, AEM CAI, DC header, S2 cat back, 00 Si cat, and a P30-A00 ECU. I used 87 octane, and timing set at 17 BTDC.

 

These were the results the day before:







All I did was swap out the cat to get the results in my previous post...