1994 Jaguar XJS 120k

I failed smog a couple years ago (high NO) and replaced the EGR valve, air filter, plugs, wires, rotor... it did not pass until I replaced the rear cat.

Fast forward to now, after 6k miles and I failed again. Here are the results:

............co2....o2.......................hc.......................co.........no(pass)
15mph 14.8.... 0 .........80 (max) -88 .......32(max) -.38 .... .. 477 -78
25mph 14.7.... 0 .........45(max) -97 ........30(max) -.56 .... ..481 -174


I failed HC and CO on both 15mpg and 25mph. Its not too far off. Do I need to replace my precats? Will changing the oil help? Air filter looks very clean. I have a new IACV, new fuel pump, new EGR... I really do not want to change everything out again unless necessary. Has anyone else been through this in CA?

 

Controversial I know. But Google "TCW3 added to gasoline" If nothing else makes a good read.

 

Things I learn by reading forums!
Forums and Google make me look a lot smarter than I really am.
(';')

 

Thank God Florida doesn't have smog tests. As Henry Ford is quoted as saying " the wind will blow it away...).

 

Need to check:
oxygen sensor.
Air flow sensor, maybe dirty.
Air pipes for leaking.

 

A oil change is never a bad idea before a smog test. Also cleaning the items xjsv12 mentioned can't hurt. Good luck with CARB rules I doubt they even consider the affects of the reformulated fuel.

 

Now THAT is a very good point!
The standards for emissions was set for the fuel at the time. Now you have me thinking!

 

ahmen!

 

The fact that I have higher HC and CO at higher rpm indicates there is an ignition problem. At least from what I read. does anyone know more about this?

 

What oil have you been using

It was reformulated in 1992 it remove things that reduce wear on your engine that would kill a converter...

If you are using oil designed for diesel or older pre cat engines that will cause cat converter failure...

 

Also ensure you have good grounds engine to chassis and exhaust to chassis. Slight voltage offsets mess with the O2 readings.

 

Well, Henry ford never went to the greater Los Angeles basin. The early Spanish explorers named it "La Bahia de Los Fuegos" translated to "Bay of Smokes"!!
and, the advent of the populace, freeways and that stuff exacerbated it horribly.
No winds to scour the basin. And a temperature inversion kept the junk down, rather than allowing it to float upwards.


We are having bad air days as dictated by a local bureuracracy. No wood burning in the fire place unless it is the only heat source. Smoke police can cite one for a violation.


I don't think t is the fuel formula. Lots of commonality even if done by different refineries. Tis the additives that are different amongst brands.


Way back when Ethyl was banned. Cars got fillers that only allowed non leaded fuels.
lead will cook a cat, wham bang. Rich or misfiring cylinders will kill a cat. don't ask.


But, although cats live long lives, it is a finite life.


And, now, zinc is suspect and modern oils have less of it if any at all. OK, in most modern engines, but not so much in older engines. The issue is valve lifter designs.
Flat tappet vs roller tappets.


And, it is almost if not so, that the cats be good and hot at test time. My local shop preaches it. I usually take a good freeway run sans OD to get them good and hot, then into the SMOG shop. So far, so good.


Carl