According to the records available, my XJ-S has never failed a smog check...until now. Even with the original O2 sensors which resulted in terrible gas mileage, the car passed. Now it's achieved Gross Polluter status.

The smog check guy seems pretty sure the O2 sensors aren't working but they're less than 5k miles old. I recently had 88 degree Celsius thermostats installed. Could they be somehow keeping the car in a cold start state? It was driven all day and running continuously for about 90 minutes prior to the test so it was as warm as could be.

Any other suspects I should be considering?

Thanks in advance,
Rhett

 

Maybe the cats?
Mine this year passed, with nowhere near those numbers and over heated and blew a hose at the same time!! thats nuts.
and your car runs great too.... hmmmm

 

The stats take all of 1min to get warm at idle on my 85 HE so that is unlikely to be your problem. O2 sensor would be my guess, just the kind of thing that is likely to fail prematurely without warning imo.

 

I asked my mechanic to look at them. Right now he seems to think it's the 82°C thermostats I had him install to replace what I believed were failing original 'stats causing the car to not get quite hot enough to tell the ECU that it's no longer in cold start and no longer needs to run rich. He's going to swap out the 82°C units for some 88° units and see if the car still fails.

The car is not misfiring or running poorly in his estimation.

 

Sounds like your mechanic is right on, CA cars need higher temps. the 88o stats are a good start. Best, JW.

 

They should be testing on a dyno in "D", but remember that the ECU will be in open loop mode (running off the internal fueling map, not using the O2 sensors) in park or neutral. You can pull the shooting loop out of the connector in the trunk to force closed loop in P and N. Shouldn't be an issue but thought it was worth throwing out as something to consider.

 

They were testing it in Drive but that's good to know.
The new 88/190 thermostats helped but not enough to pass. This time, they checked both banks and they fail the same so whatever is wrong is either upstream from the exhaust or common to both (two failed cats, two failed 02 sensors, etc.). The good news is that even with 88/190 'stats, the car isn't overheating at idle so it looks like that problem was (a) bad thermostat(s).

Also, he says he's 100% confident that the engine is in good shape.

Next he'll check the cats, the o2 sensors, the ECU, the manifold absolute pressure sensor and...

 

I'll bet it's over fueling, then. Check the air and coolant temp sensors - the electric ones used by the ECU (ATS & CTS). Might be the TPS (throttle position sensor), that might be just an adjustment. I had a bad intake manifold leak - the PO tried to seal it up with gasket maker... from the outside, without disassembling it. Might have worked, sort of, for a while. That was one of the issues on mine.

 

Just talked with my mechanic. He's checked all the sensors and the cats. The cats are, in his opinion, borderline. Because replacing them is costly, he's going to swap out the ECU in the boot with one he knows is working. If that works, we'll buy a replacement (or two). If not, then it's down to the cats, I guess.

 

Man, I thought things were bad in New York State. Luckily we don't have that test... yet.

I'm curious how that works for older cars - is there a cut off, where cars made before a certain date don't have to do this test? If your car is over a certain age, is there anything about that? I just can't imagine a barley driven 26 year old car being the cause of global warming. What do people with older cars do in CA. Sell them or move?

 

The cut off is fixed - 1976 model year and older are exempt. California is trying to get as many old cars off the road as possible. Makes it tricky to own older cars. But... the Jag burns pretty clean when its running right and can pass handily when behaving.

Rhett - Magnaflow makes a universal cat that is CARB approved that will weld on. It'll take a single cat per side - they're rated for something like 3.2 liters displacement each. If you can't find them let me know and I'll dig up the part number. I saw somewhere that they'll fit where the cats by the transmission go. They're roughly $130 each, probably be another hundred to get them welded up? Definately cheaper than replacing with stock.

 

Oh, yes, please! We've eliminated pretty much everything else. My mechanic replaced the passenger side fuel pressure regulator which was allowing too much fuel into the injectors so that might be it but he said the CATs are marginal as well. I'm really hoping for a single smoking gun as it were but I have a feeling this is more of a combination off issues.

As to the laws here in California, any car prior to 1975 is exempt but everything built after that must pass a modern emissions standards.

 

different temperature thermostats DO NOT affect the operating temperature of the engine. They only affect how it warms up. While yes a 100 degree thermostat wouldn't open as early as a 82 degree and increase engine temp we are talking about 2 thermostats BOTH opening before the desired operating temperature so either way if the car runs at 200 degrees it runs at 200 degrees.

if you had to replace the o2s the id wager the cats are damaged ( they are also very old). replace them

 

'75, yeah, that's what I meant. Lost again in the endless maze of state regulations.

There are several listed but I think this is it:
MagnaFlow Catalytic Converters - 49-STATE & CANADA Catalytic Converters For Trucks, Suv's, American Muscle, Diesel, & Sport Compact Vehicles

Scroll down and it lists your model year. What I'm not certain of ids whether you can just put one per side on or if they want you to keep four. They list a front and a back:
MagnaFlow Catalytic Converters - 49-STATE & CANADA Catalytic Converters For Trucks, Suv's, American Muscle, Diesel, & Sport Compact Vehicles

Ones $121 and the other $123 on Amazon... Even doing all four should be "only" around 500 bucks.. About half what I've seen for the least expensive bolt up solutions I've found.

I'll likely have to do the same. One thing to make sure of ... Apparently the upper headers have some kind of "honeycomb" structure inside that serves no (?) useful purpose but to restrict exhaust flow. I intend to check and make sure that if I've got it that it is removed.

 

What about a bottle of that stuff at the auto so "guaranteed to pass". Not sure what it does our if it works.
If it is rich then it means UN metered air is getting in. O2 sensor then increases fuel.

 

Passenger side being right side, yes?

I'm afraid the RH (inlet) regulator can't cause too much fuel into the injectors. It could allow too little, but not too much. Truth is, he could have removed and bypassed it, and thrown it in the trash, and the engine wouldn't be any the wiser :-)

It's the LH (outlet) regulator that controls fuel pressure. Only a fuel pressure test will tell if it is regulating properly.

But, yes, excessive pressure will cause rich running.

Cheers
DD

 

On top of everything else....it sounds like he's covering all the bases....make sure he checks the two "load enrichment' switches. One electric, (right side of throttle capstain) one vacuum (bolted to the RH inlet manifold, well towards the rear). If either of these are faulty (that is, operating when they shouldn't be) you'll get about 13% enrichment!

Cheers
DD

 

Yes, but the FI system on this model doesn't rely on air metering for mixture control. Instead, it uses a baro sensor.

If there's an air leak of some kind the fuel injection system doesn't know where it's coming from. The baro sensor "sees " the leak simply as a throttle that is opened a bit wider (and, in fact, with an air leak the engine speed will increase) and responds to the extra incoming air by increasing the injector pulse width, thus keeping the mixture in balance.



Cheers
DD

 

Wouldn't a smoke machine find this?

 

Sure, I don't see why not.

Cheers
DD