I think I am finally giving up trying to solve the NOx emissions problem with NJ inspections. Between frequent out-of-town business trips, I'll send it to the shop to have it fixed.

But first I need to fix the speedometer. I replaced the capacitor behind the gage with one from Radioshack. No dice. This afternoon I removed the speedometer pickup on the differential. Is there a way to test it? I don't want to spend a hundred bucks getting a new one from the dealer and then find out I guessed wrong.

Oh by the way, what fluid do I use to top up the differential housing? When I removed the speedometer pickup, differential fluid started dripping out.

Did you ever figure out the culprit causing your NOx emissions problem. I have
a 1990 240 wagon and it failed the NJ NOx test today with a reading of 3501 vs.
an acceptable level of 1273.

Any insight into how you (or your pro mechanic) solve your problem would
be appreciated.

Regards,

Joe Walsh

My 93 940 wagon was due for NJ State inspection 10/2002. First I forgot about it, thinking it was due 10/2003. When a police office reminded me by issuing a ticket, it was, oh, May, 2003 IIRC. After a year long struggle with one single persistent item, NOx, it passed two days ago. During that time I got another ticket (daughter was driving to Newark airport to pick us up), spent about $700 to $800. As I said I was going to give in and bring it to a garage. It was a miracle no less when it passed.

The list of what I did in roughly chronological order:

1. Replaced spark plugs after first inspections with high NOx. No good, NOx was still high.
2. Replaced complete exhaust from the header down and the original O2 sensor with a Walker O2 sensor. No good. The exhaust was nearly due in any case so it not a complete loss.
3. Cleaned the Air Mass Meter, throttle body and the crank case. No good.
4. Replaced the Walker O2 sensor with an oem O2 sensor. Passed.

The above does not include several interim inspection trips to buy time. Each trip buys me 45 days. And I did everything myself.

I don't know your situation. The lesson learned for me is to use the oem O2 sensor. I spliced the wires of the Walker O2 sensor. It may have been the wrong sensor or I may have spliced the wrong wires or both. For the $60 difference in price, it is really not worth it. The oem sensor comes with connectors ready to plug in.

If your HC and CO numbers are good, I'd say the cat is okay. Try replacing the O2 sensor. Mine doesn't have EGR, BTW. Oh, check vacuum leaks before replacing the sensor. It may be as simple as a vacuum leak somewhere.