I have a 1993 XJR-S which has failed the smog test- any suggestions on what to do? the car runs hot- but still has a lot of power. not sure my options. it is #40 out of 100.

 

The emissions test has several elements/measurements so a bit of detail as to which aspect of the test resulted in a 'fail' would be helpful.

Over-rich mixture/over-fueling is a common cause of a 'fail' result. You might want to scroll down a view some recent postings.....there are a couple of recent threads on rich mixture and emissions testing.

How hot is 'the car runs hot' ?

Cheers
DD

 

All good Q's from Doug I would be interested in the answers as well.
It was my experience when I was dealing with CA smog testing, that a fresh oil change was always a good investment. You would be surprised how many snog problems are solved with fresh oil.

 

So when they do the smog test, do they test both banks as the exhausts have no crossover or could one side be good and one side be bad and they would never know?

 

They should do both banks seperately (they do over here).
On the earlier XJRS you could apparantly adjust the CO2 level at the ECU (no idea how, perhaps someone could chip in?).
My recent purchase (1989 XJRS) shows several failures in the past, all cleared by the addition of injector cleaner and an Italian tune up.

 

There is also a link in the engine bay that can be removed I believe to lean out the ecu. I think I read that in Kirby's book. I see a yellow loop on my 95 on the left hand side I presume is it. Any one confirm?

 

Just wanted to thank you guys for your input and sorry i haven't had a chance to respond.
my father bought this car - used in 2006- after a 5 way cardiac bypass- it had 30, 000 miles on it at the time- He passed away four years ago- I shipped it down to California and did an extreme tune up on it- new plugs, new filters, about 4k worth of work. two years ago it failed the smog test- multiple times. the mechanic was stumped- of course after 2k plus more work- still failed.
i took it to another neighbor'HOOD' shop- he welled on two new converts ( i think) and it miraculously passed- I only drove it 200 miles since then and it failed a few months ago

HC- 128 and 137
NO- 1169 and 1240
not sure what to do- i am hanging on to it cuz of my dad- it is number 40 out of 100. any ideas?

 

**Snake Oil Alert - Don't say I didn't warn you. **

If you've only driven the car 200 miles in 2 years, that could be a big part of the problem. Modern gas (especially ethanol) goes bad after a few months and will leave a residue all through the fuel system.

If your CO2/CO are within range, your cats are probably working well enough. But you probably have old gas that needs flushed out. It is likely weak (lower octane) and isn't burning clean due to the gas breaking down. If you've ever started a mower with last years gas you will probably notice that it tends to smoke a lot more than after it's been run a few passes over the yard.

So first: I'd run two full tanks of 93 octane Shell or Exxon (Ethanol Free Marine Grade if you can find it) and go for a drive.

Now here is where the Snake Oil comes in: I would run two cans of Seafoam or Chevron fuel system cleaner with it. I'm not saying that you need more than a can a year after that (if you only ran Shell 93, you probably wouldn't need any) but if you run the car that little I'd at least keep fuel stabilizer in it regularly.

All of these chemicals are basically detergents of some type or another and for them to work requires a) mixing with what's left of the bad gas to get it to burn and b) soaking the parts of the fuel system to get the varnish out. This can also help "clean" the spark plugs (which can also foul from a lack of use). This ends the snake oil segment. (I use Seafoam once a year in my cars and in my mower in the spring. I use Stabil in anything that I think may sit for more than a few months.)

And this drive needs to be where you will be accelerating the engine some, not just a leisurely cruise on the freeway, but not stop and go traffic either. The engine needs to rev up and down. I'm not saying redline it, but get it up above 3000 a few times after its warmed up. (google the "Italian Tune Up" SteveM mentioned).

So after you've "cleaned" the fuel system, make sure your plugs and ignition are good: if an ignition part is 5+ years old it needs replaced or at least tested. The slightest miss lets fuel by that burns in the Cat instead of exploding in the Cyl and will ruin a emissions test.

Lastly, you need to take the test when the engine has been running for a bit. An engine runs at peak efficiency when it's warm and (typically) somewhere around the top of the torque curve.

YMMV. Good luck.

 

Sparky has pretty much nailed it these cars need to be driven. As for the snake oil I have been using Berrymans B12 it works very well here in the Mountains of Nevada. Its in the XJS and the Towncar and most everything else here at the ranch.