I have been chasing a strange problem (to me of course). I found the rubber hose going from the check value (coming from the air pump) to the air rail worked loose which I put back. I didn't pay much attention until a few days later the engine got fairly hot, started a loud noise, and I found the air rail broken at the weld. (Literally unwelded) I changed it and also a cracked rear manifold. Now I have a crack around the flange of the front catalytic converter. And the hose came off again. The engine has lost power, hardly able to get to 3000 rpm. The engine seemed hot to me but the temp gauge never got above 90.

Could a "clogged" converter cause this? I have heard of converters being clogged but never encountered one. How would I check?
Also since I must replace or repair the converter, I thought of maybe going with a non catalytic replacement. Cheaper. If I did that what should I do about the oxygen sensor going to the fuel injection.
Thanks for your advice
Dick

Submitted by NE40-29744 on Wed, 08/12/2009 - 08:44

Just a short follow up note especially to JAM and Dick Maury. I removed the front converter and because it was cracked at the flange I removed the whole top. The converter was very obviously clogged. There was a thin layer of something only about 1/16th thick but covering the front surface completely. So I gutted the converter and had it welded back together. I did not replace the rear converter because the back part of the front converter looked so clean. I may still replace the rear at some point. It breathes much better and has improved power. But a bit more engine noise. No back pressure when I check. I think I'll run it just a bit and check the plugs.

I still have a cut out problem around 3500 rpm but I am not sure its related. I suspected the fuel filter but no. I changed the fuel pump when I found about 40 lbs pressure at the fuel rail. I want to go over the standard things like vacuum leaks, throttle position, timing.
Again thanks for the good advice.
Dick

Submitted by zurdo_1@univis… on Sat, 08/01/2009 - 09:57

yes, do not drive it with the front cat in place, remove it and "process" it. It is not a piece of cake to remove but with a little patience it will come out. If your car still has the original cat,
they always crack at the flange, so that's normal. And that's where you open them up.

If the hose keeps sliding out of the rail's nipple, are you sure the hose diameter is correct? it could be too big. It should go in tight then clamped in place. Rub a little hand detergent or vaseline to both parts so it will go on easier. Use Gates Heater Hose which you can get at any auto parts store.

Submitted by NE40-29744 on Sat, 08/01/2009 - 07:28

Thanks for the advice JAM. I have been thinking of doing something like that. But as Dick Maury notes I would also like to find the "root cause" before driving very much Actually I already have the Y pipe and have replaced the manifold and air rail with used units, both of which I painted!. I was able to confirm Maury's theory by checking the pressure. >25 lbs. So yes the cats need attention But likely something else as well .
Thanks
Dick

85 XJ6
64 E- type FHC

Submitted by zurdo_1@univis… on Fri, 07/31/2009 - 15:52

Richard,
depending on the state where you live, you can remove the catalytic, open it up, remove all the garbage in there, clean it inside, re-weld it, pressure test it, and re-install it. That's how I did mine.

Incredibly, the car passes inspection without either of the two cats. At this point and time in the life of your car, installing new cats is a waste of money.

Air Rail: re-weld the air rail weld, it was probably a weak one anyway, and you've resolved two birds, After removing it, have it blasted to clean it inside too, then paint it silver with engine paint.

Cracked manifold: you can find a good used rear manifold on eBay for little money. Let me know if you can't find one and I can direct you to a source who has them.

Last, you can replace the Y pipe catalytic with a new Euro-style Y pipe which has no cat. The engine will breathe better, the hot spot under the driver dissapears. If you want to simply eliminate the front/down catatytic, you can also order the Euro-style down pipe, cut the O2 Sensor "bong" off the old cat, and weld it to the new cat-less down pipe.

JAM

Submitted by rcmaury@bellso… on Fri, 07/31/2009 - 09:52

There usually is a problem. It could be bad gasoline or an additive, ignition or cam timing, faulty o2 sensor, one or more injectors. I would suggest that you have it checked out professionally if it seems to be running correctly. My XJ6/3 now belongs to a friend and with over 400,000 miles, still has the original cats. A standard compression gauge does not work for this and yes the engine must be running as there is no back pressure without it running. A vacuum/pressure gauge available at most auto parts stores reads about 10 psi which is more than enough to tell if you have a problem. If you remove the 02 sensor, that will usually be enough of a relief to at least let it idle. If you check your spark plugs, they will most likely be black and sooty from carbon build up due to the backpressure.

Submitted by NE40-29744 on Fri, 07/31/2009 - 08:24

Thanks Dick,
Assume you mean with the engine running? Only gauge I have here is a compression tester. Can I get anything useful by just cranking? Probably not.
Any ideas what engine running problem could cause this? I have checked compression in case a blown head gasket. All read around 165. Plugs look OK. Changed the fuel pump when I only got 40 lbs pressure. I just haven't found anything that would have caused it yet!

Submitted by rcmaury@bellso… on Fri, 07/31/2009 - 08:12

Typical symptoms of a clogged converter. You can verify by pulling the O2 xensor and attaching a pressure gauge in the hole. Then you rap the engine revs and watch the gauge, It it goes up past 5 psi, you have problems. From your symptoms, the needle will probably wrap around the gauge. The air rail came apart from exhaust gases trying to find a way out and heating up things with a lot of pressure and heat. Don't just replace the converter as there is most likely a engine running condition causing it. Not fixing the running problem will just hurt the new catalitic converter.