Nox rate failed smog

[Darkcloud]

Went to to do a smog test failed smog on the NO(PPM)

I passed everything but the NO (ppm)

The numbers are

Max/ave/mea
15 MPH 559/298/789 Fail
25 MPH 516/234/508

I only passed on evertthing tho with fyling colors

1 week prior I did a full tune up and seafoamed the car. I run 89 in the tank maybe I'll start running 91. Change 02 sensor

What could cause such a high no reading

[Bravo-man]

Clean your egr ports. The best way is removing the intake man.

[Darkcloud]

I'll be doing that anything else I can do

[PhatAccord]

Yeah cleaning the ports should help. If I remember correctly; you can actually drill the intake runners close to the head, clean out the build up and then plug up the holes with caps. (which Honda sells)

[408cb7]

i had the same issues with my accord, passed everything but the NO part, i cleaned the egr ports, changed my sparkplugs and made sure that timing was set correctly using a light gun. my car was of by a couple degrees , after that it passed with flying colors all across.

[wed3k]

91 octane and retard timing to 13 degrees. (you are allowed up to 3 unless specified)

california fucking sucks. 500ppm nox for an early 90's car? they must be high.

['93CB7Ex]

Yea retard the timing and it should drop down.

[ferenza]

Since you seafoamed the car pull the sparks out,clean them off and regap them.if you havent replace them since buying the car,replace.clean out your egr and retard the timing a bit.

[Darkcloud]

Seafoamed before tune up.

Could a bad cat cause high nox

[90blackcoupe]

91 octane and retard timing to 13 degrees. (you are allowed up to 3 unless specified)

california fucking sucks. 500ppm nox for an early 90's car? they must be high.

Our limit on the 25/25 for nox is ontario on a cb is 467, and most cb's that come in blow around 200range the ones that come in an pass that is lol, heck my cb blew 91ppm out of 467ppm, so 500 is pretty leniant for cali, yes I know the temp is different in cali then ontario but still.

[wed3k]

wowzers thats amaxing. ive seen a lot of 5th gens and preludes fail for nox.

[ferenza]

Seafoamed before tune up.

Could a bad cat cause high nox

It can but if your passing the high speed test i think the cat is working. high nox means you are running really lean.Does your cb have a slight stumble when its idling?

[10thAnnivCB7]

i 5 gas tested my car at school and my nox failed at idle due to a vacuum leak but it got better as i increased the speed

[90blackcoupe]

yea most 4th gens and 5th gens do fail had a few ludes fail but that's the owners fault for lack of maintenance, most vtec engines pass compare to non vtec

[wed3k]

unfortunately egr port cleaning isn't a scheduled maintainence.