I've read through the forum all I could. Confused!


Went to get my XJ6 smogged here in Calif and twice she won't pass as she's "leaving too much unburned fuel in the exhaust." Runs like a swiss watch otherwise. I'm thinking sparkplugs. Just going to throw in some new ones tomorrow but want to get the right ones. Hot/Cold, NGK/Champions, gap, etc., etc.??


A brief bit of help would be most appreciated at this point.


PS: 1987 Series III. One of the last. Does need to be taken out and run I know as most trips are short 2-3 mile stop and go. Did take it out for a 20 mile freeway run today before the last smog check. Still came back not passing smog. Threw a can of Sea Foam in each tank and filled up. New PVC valve last week hoping that was all it was but test exactly the same

 

New plugs wont hurt but if you are not detecting any misfires then make sure to also check your ignition timing too. Plugs can tell a story so check each one and google how to read a plug. Run a bottle or two of fuel injector cleaner and take it a nice hot high speed blast on an open road. Make sure your cooling system is full becuase if the level drops the coolant temp wont see water and may richen the fuel mixture. Only mess with the AFM as a last resort when everything else checks out.

 

Service manual calls for N12Y plugs.

.025 gap for pre 81 cars and .035 there after.

My opinion is any name brand copper plug should suffice.

 

Put in a set of NGK' BP5ES's set at 0.36. The old Champion RN12YC's came out really clean and even so no problem there. Took the XJ into the smog after the plug change and a very nice long 2 hour drive toward Yuma and then had it re-checked. No a bit of difference in the readings! Back to the drawing boards!! Still running rich.

 

Do not overlook the catalytic converter.
They can become filled with carbon and fail to burn unspent fuel.
Also make sure that the gas cap seals are working, well.
Try to find an inexpensive exhaust analyzer and check the exhaust before you do another smog test.

http://www.innovatemotorsports.com/products/lm2.php

 

There are 2 catalytic converter's on the car. Obviously, they operate separately. The sniffer's been up only the driver's side one. I wonder what the reading might be if they run it off the passenger's side?


Gas tank lid seals I believe are working as I hear that 'sucking' sound when they're released to fill the tank.

 

Shouldn't be a difference, as it's a single exhaust until *after* the catalytic convertors....when it then branches off into dual exhaust.





A tiny whoosh is typical if the tanks are run low. If it's quite a dramatic whoosh....that can be a bad thing, even to the point of causing tank damage as the vacuum is enough to flex the tanks. You might have a problem with the check valve at the vapor canister. Most of us disconnect it or drill it open. Jose has pics

Cheers
DD

 

This might help

XJ6 Series - EFI Rich Mixture


Cheers
DD

 

how warmed up was the engine when you took it for the smog test?

one time my '84 failed and I went straight to my mechanic. He asked me the same question. I answered, from my house to the smog station is about 15 minutes.

His answer was: take it for a long drive, at least 1 hour or better, then take it to the smog station. I did, and it passed.

 

I think the gas tank seal issue is a red herring for cars of this age. CA does have a test requirement for leaking gas caps. but, the application is limited.


And, it has nothing to do with combustion, merely the escape of vapors from the fuel tanks into the atmosphere. Mine are far from leak proof and so far passes SMOG just fine. I have the diaphrams, but far down on my todo list.


And,as a practical matter the lid type fillers on our cars probably preclude fitting nt detector by the SMOG station.


Mixture control seems to be the place to investigate.


And, yes, operating temperature is critical as to the engine itself as well as the catalyctic converters. Even my SMOG guy counsels a good run. But, loafing in OD isn't enough. And that is what a Jag's 2.88 ratio is effectively.


San Diego towards Yuma. As far as my old stomping grounds, El Centro???


Yeah, the S3 exhaust isn't a true dual pipe system. Merely dual from the last cat back. Better exhausting or merely stylish, I dunno. Perhaps a way to solve the through the cage with enough area???


Carl

 

the semi-dual system started after the MK-2; All Jaguars had it starting with the MK-10, then the S type, then the 420-G, then the 420, and all XJ Series since including the XK-40 onwards.

there must be a reason other than cosmetics, in fact all other car manufacturers started copying the Jaguar exhaust system in the early 1990's, including the triangular tail lamps.

Yes, operating temperature, get that engine hot and stabilized before taking it to the smog test. At least 20 open-close cycles of the thermostat. If nothing changes, at least you had a good long ride, that's what Jaguars are for.

 

MONEY!!!! The factory's noted Hot Rods. Dual pipes an absolute requisite by any guy claiming to be a Hot Rodder. Me too. I plumbed up a pair for my 27 T Ford four banger.


And, some factory big wigs were hot rod guys.


71 or so through 78 IHC Scout II's had true dual pipes on the 304 and 345 truck engines. sounded tough. Alas, 79, gotta have catalyctic converters. Whoah, two of 'em?? Naaah, single exhaust with an awful crimp. The awful pancake cat as well. GM sourced. I rustled up a later Ford cat. Big, but longish. Better tech as well. Then had the muffler shop make a set of duals with a pair of small turbo mufflers. Much better all the way around. A SMOG illegal conversion, yeah possibly. But, it was well done and looked right so it passed. Albeit with some effort as the IHC 304 truck engoine was inherently "dirty". Tough as nails, though.


So for sexiness at a price, the factories used one cat and one muffler with two pipes back.


I used the guts of a 94 Cadillac Fleetwood Brougham for my Jaguar. 'The SMOG guy didn't like the true dual exhaust. Other LT1 cars used the fake dual system. My Factory manual proved my install was correct.


CA's idea was that two cats were not as good as one. We do that illogic thing quite well!!


Now in the throes of vaccinate kids for measles and other stuff or not. Law says parents can exempt their kids on beliefs. Poor kids. Not only theirs but others!!!!!


Carl

 

Sat with an old hotrodder friend for b'fast today and he said the same about getting the car 'HOT'. It dawned on me that I had a new radiator and thermostat put in last year and the temp gauge has never reached the midpoint. My buddy said the old trick is to put a piece of cardboard infront of the radiator and get the engine HOT before the smog check. Makes sense if the car thinks and is actually running cooler. It still runs very, very well but I guess the cooler running due to the new radiator might be throwing off the mixture.


Tomorrow I try the piece of cardboard technique and see if that allows things to get to a leaner mixture.

 

You need to get it up to 80ºC or so to get it fully outside of the 'cold enrichment' phase.

Cheers
DD

 

Yup!


I did the cardboard in front of the radiator thing to get my IHC to run a tad on the hot side of the guage.


Also, screwed down the idle jets til it would just barely run. Twas a carb'd engine.


Obviously, not applicable to EFI cars.


Now that I think of it, I used similar tactics on my 85 F150 4x4 powered by the first FI'd Ford 302 truck.


It came with a simple single muffler single cat, single tail pipe. Son gave me a cat back dual set. Two pipes out of the same muffler. If there was any performance increase, I didn't feel it. Looked a tad better, though.


The 351 powered trucks came with a similar cat back dual set up.


Carl

 

My smog check passed ok this morning. I'd put the cardboard in front of the radiator and it only went up about 10C degrees but got it to just around the 90C mark. Not wanting to have a failure, some of that Mexican taco sauce went into the tank, about a gallon of it to 5 gallons of premium that was in there. Can't say if there was any increase in the power levels however but it did pass smog!

 

Leaking gas cap seals, will allow water to get into the gas tanks and cause rust and lower the octane, if a lot of water intrudes.