how do you fix if nitrogen oxide is high on smog check

[ryunosuke]

so just and got my smog check done today for my 1992 toyota mr2 2.2L , and did not pass because it says that my nitrogen oxide is high being that at 15 mph the max is 807 and i got 1338 and then at 25 mph the max is 746 and i got 1728, wat type of problem does that suggest is going on with my car the smog tech said it is prob something to do with my air fule mix but how do i fix that please help

[tHa kNiGHt FaLL]

unless your car runs very lean which i doubt... only two things control NOX and thats your EGR system and catalytic converter. take your smog results to mieneke and pay 50.00 for a failed smog diagnosis.

too many variable and its very hard to check your cat and very hard to explain how to test your egr

[Doctor J]

What are the HC/O2 readings?

[ryunosuke]

my HC is at 15mph the MAX is 121 , the AVE is 31 , my MEAS is 15
20mph the MAX is 96 , the AVE is 20, my MEAS is 13

O2 is MEAS 0.1 at 15mph at 1896RPM, and MEAS 0.1 at 20mph at 2091RPM

CO2 is MEAS 14.5 at 15mph at 1896RPM, and MEAS 14.5 at 20 mph at 2091RPM

my CO 15mph the MAX is 0.76 , the AVE is 0.10 , my MEAS is 0.03
20mph the MAX is 0.65 , the AVE is 0.09 , my MEAS is 0.02

my NO 15mhp the MAX is 807 , the AVE is 237 , my MEAS is 1338 FAIL
20mph the MAX is 746 , the AVE is 199 , my MEAS is 1728 FAIL

everything else pass

i did have a non name brand short ram intake on when i took the test thought also does this help at all?

[toyomoho]

Anything that increases combustion temps will increase N0 levels. A lean engine will produce more N0. Issues to check:

Coolant system problems that raise coolant temps, leaky intake manifold gasket or vacuum hose leaks, defective 02 sensor, defective EGR system resulting in less exhaust gases being recycled into the engine intake; improper spark advance, initial timing incorrect; knock retard system not working correctly, carbon deposits on valves.

[Doctor J]

Based on low HC and low O2 readings could say that:

• the engine is running on its top combustion efficiency and there is no misfire
• the catalyst is good

You just need to inspect the EGR system:

• • make sure that EGR backpressure signal hose is connected to EGR valve and vacuum modulator
  • check signal vacuum ports at throttle body to make sure they are not plugged up
  • check the BVCV that it opens when engine at normal temperature
  • check the vacuum modulator for ruptured diaphragm
  • clean EGR valve,tube and transfer port at intake plenum

[ShawnM]

Most Nox issues are due to EGR system problems. Though anything is a guess untill its actually checked out.

[ryunosuke]

^_^ thank you very much I will give that a try

[tHa kNiGHt FaLL]

i had perfect readings and failed on NOX only... and my catalyst was the problem.


and toyomoho more than half your reasons are caught during a California Smog Inspection.

If there are engine codes they won't run they test, timing off more than 2 degrees they won't run the test. All monitors and readiness codes need to be set, and a vacuum leak will cause you run rich. which is hi CO levels... and it obvious that your car is overheating.

like i said... only two things fundamentally control NOX... and thats the EGR and the CAT.

apply vacuum to the negative back pressure transducer type EGR and the engine should stumble. release and it should return to idle.

if not... you have a CAT issue

[Doctor J]

Not working cat most likely gives around 700ppm NO, 0.5%CO, 140ppm HC.

[4bunny]

I have a 1996 4Runner and I failed smog due to elevated NO as well. I took it to the dealer and I was told that I had a leaky head gasket and some water & coolant was leaking into cylinder #6 and that was cuasing a misfire. Apparently, my car was getting too hot and caused the head gasket to crack and potentially warped the heads (amzingly enough, I never overheated so I never would have known there was a problem).

I am looking to sell it and I will not pay a huge sum to fix it at this point. Now I am wondering what shortcuts I can take to smog the vehicle.

Radiator stop leak? (will it stop coolant from blowing into the cylinder)
Motor Honey?

Any ideas?

[GTSTWINCAM]

I have a 91 Celica GT-S and I too, failed the smog.


Smog results:

15mph
HC Max 121 Avg 31 Meas 38 PASS
CO .76 avg .10 meas .44 PASS
NO Max 807 avg 237 meas 1834 FAIL

25mph
HC Max 96 avg 20 meas 32 PASS
CO Max .65 avg 0.09 meas .51 PASS
NO Max 746 avg 199 meas 1458 FAIL


Check Engine light Code 71.

I dont feel any vacuum from Port R of the throttle body.

Is that normal? I cleaned all the ports with a compressor.

[hmong337]

I had the same problems as you have now... however, you want to pass like how i did?

What to do:

-buy a timing light (if you don't have one already)
-get a paperclip
-fill up on the highest octane fuel you can find at your local pump
-set the paperclip in TE1 and E1 terminals in your diagnosis port.
-loosen the distributor cap screws to retard the timing
-set the timing with the timing light to around 3' TDC
-GO TEST AND PASS

-Once passed, set the timing back to 10' TDC and you're smooth sailin'

[GTSTWINCAM]

Originally Posted by hmong337

I had the same problems as you have now... however, you want to pass like how i did?

What to do:

-buy a timing light (if you don't have one already)
-get a paperclip
-fill up on the highest octane fuel you can find at your local pump
-set the paperclip in TE1 and E1 terminals in your diagnosis port.
-loosen the distributor cap screws to retard the timing
-set the timing with the timing light to around 3' TDC
-GO TEST AND PASS

-Once passed, set the timing back to 10' TDC and you're smooth sailin'

Cant do that in California. You will fail for incorrect ignition timing..

[MR2Jedi]

Originally Posted by GTSTWINCAM

Cant do that in California. You will fail for incorrect ignition timing..

They check engine timing in Cali. ?
Wow, didn't know that....