Civic emission issue

[HotHordas7]

I got a '90 civic D15b1 that failed emission test:( . It failed on the NOx ppm reading 1831 out of 1440 allowed on the 25/25 test; and 2085 out of 1577 allowed. The guy that did the emission said it is not burning the fuel as it should in order to pass oh and also I forgot the other guy that worked there timing should be adjusted (he guess). Any helpful tips, suggestions or if anyone had a similar problem sharing it with me would be appreciated.:D

[81911SC]

EGR?

[baby50]

checked the ECU for any codes? Also check the TW(tempature water) sensor near the thermostat and make sure it has a good connection. On EF's this can through your N0x reading off. If it burning fuel issue then you have a list of things that could cause that. Spark plugs, fuel injectors, fuel pressure regulator so that is why i say check the ECU first.

[toxxxic]

mine failed for the same reason.

i retarded the timing & it passed.

[thepolecat]

cant that sometimes be a cat converter problem- I think it was on mine one time.

[toxxxic]

^ yeah if its clogged / old

[HotHordas7]

This engine does not have an EGR. I retarded the timing and I failed to mention the cat on the car is newly installed, at least it looks like it. The car FAILED AGAIN today and now the numbers went throught the roof. On NOx under 25/25 test it read 2865 (vs. 1831 last time) out of 1440 allowed; and on the 50/15 test it read 2783 (vs. 2085 last time) out of 1577 allowed. Also HC went up on 50/15 test barely passing by 1 point @ 202.

[HotHordas7]

Oh and I also checked the ECU and it just flashed once and that's it and the check engine light is not on.

[Tensa_Zanget]

usually high NOx is because of bad cat, O2 sensor. Try driving for a good 30 mins then immediately head to the emission place so then ur cat can warm up. goodluck