Failed emissions test

[sw2765j30]

My 1995 J30 failed the emissions test this year because of the NOx ppm levels were too high. The check engine light is not on so I don't think there is an error code to be read. I would like help in knowing a possible source for the problem and ideas on trouble shooting this issue. Thanks in advance for your ideas.

[driverdriver]

Welcome to NICO!!!

First order of business is to check your ECU for codes. If you don't know how to do it, there is a "sticky" at the top of the forum. Click the one that falls within your model year.

Is your vehicle well maintained? Do you only run premium gas through the tank( a requirement for the J and not an option)? Are oil changes regular? Is the vehicle tuned up?

Let us know.

[Ebbtide]

I would think your egr system is the culprit. Probably clogged tubes, pretty common problem.

[elan]

Mine failed it too I cleaned the EGR tubes ($200 at Nissan dealership) and the readings has reduced twice - passedalso check if the EGR valve is not stuck you can reach it at the back of the engine and try to press on the valve from the bottom - if it moves it's likely ok just try to clean the tubes

if you have never done it - it's time to do.

[sw2765j30]

The car has 194,000 miles and is in good condition. I change the oil every 3,000 miles. It is getting close to needing a tune up but it runs very well. Only run premium gas. My son is driving it to school now so i don't drive anymore but it is one of my favorite cars. I checked the ecu codes and found 32 and 54. When I went to check it additional times it only would give a 55 code which is not on the list of codes. I am guessing that means I would need to drive it so it can reset?

I located the egr valve but am not sure which tubes need cleaned. I will look for a picture to help me determine what needs cleaned. The valve can be pushed up and down from below. Any advice on the cleaning process will be appreciated.

Thanks again for the quick and helpful replys.

Steve

[sw2765j30]

I read in a another thread that Yodawill2000 had directions for cleaning the egr tubes. If yodawill2000 reads this and you still have them please send to me. Thanks. How do I contact a member of this board through email?

[yodawill2000]

On either side of the plenum you will see a pipe coming from the rear of the engine then turning up into the Intake manifold. They are held in by two small bolts. Don't recall the size.Remove those and the pipe will pull down out of the manifold. The holes that were clogged on mine face the rear of the car. Carefully remove the carbon making sure alot doesn't fall back into the tube. Then push the tubes back up into the manifold and secure the bolts. You will have to remove the dipstick brace on the passenger side.But all in all its pretty simple.

[sw2765j30]

Thanks for the quick response and the details on cleaning the tubes. I will have time on Monday to tackle this. I'll post the results. Thanks again.

[sw2765j30]

Update. Thanks for all the advice. I cleaned the tubes last Monday and the car passed inspection! I only dropped the tubes in the front and used carberator cleaner and pipe cleaners to remove the carbon that I could. They both were clogged approx 3-4 inches back in tube. The NOx readings went from 900 ppm to 62ppm. The advice from the forum was very helpful. I located a pdf file service manual online and it offered pictures etc but not specific directions on this job. There is a support screw at the rear of the engine on each side which I had to remove in order to get enough movement in the tube to reinstall. Discovering this slowed the job but it is doable for the occasional mechanic/troubleshooter. Thanks again for the help.

[GerryO]

Update. Thanks for all the advice. I cleaned the tubes last Monday and the car passed inspection! I only dropped the tubes in the front and used carberator cleaner and pipe cleaners to remove the carbon that I could. They both were clogged approx 3-4 inches back in tube. The NOx readings went from 900 ppm to 62ppm. The advice from the forum was very helpful. I located a pdf file service manual online and it offered pictures etc but not specific directions on this job. There is a support screw at the rear of the engine on each side which I had to remove in order to get enough movement in the tube to reinstall. Discovering this slowed the job but it is doable for the occasional mechanic/troubleshooter. Thanks again for the help.

Nice work and it's great to hear the details and about the final out-come/end-results, especially when it is so good!

[Q45tech]

Important to understand the function of EGR in all engines for the past 25 years to reduce Nox at cruise and to improve highway MPG by at least 1 MPG sometimes 2.

Perfect EGR [as brand new] is necessary to reduce transistional rpm knock.Sudden throttle opening before transmission down shifts to lower gear for acceleration.

Untrained wait until an emission failure and have lost money [MPG] as it progressively clogged up for years.

On my Q I have cleaned EGR every 2 years or 30k for past 318,000 miles.

Probably saved 400 gallons over 18 years.............probably a breakeven laborwise but sure improves transistional knock. Probably should have stretched the cleaning to 4 years 60k in the first 8 years before blowby even started.

Don't forget PCV cleaning or replacement.