Hello – I'm a new member to this forum. Have read many great threads and information.
I have a couple problems with my 2001 S-Type 4.0l.

The check engine light is on constantly (amber if that makes a difference) and my code reader won't get the codes. It goes through the entire scan then displays “link connection error'. It works fine on my 2003 Avalon and 2003 Chevy Silverado 1-ton Duramax, as well as a friends later model XJS. Have read the comments here about the code scanners and can afford one of the Bluetooth with Torque app so will order one.

The engine has a slight miss and under a load it stumbles; giving it more throttle to downshift only make the stumble worst and the 'check engine' light flashes on and off.

Second problem is the A/C. Blows slight cool and my low side gauge shows 30 pounds pressure when should be 50 with my air temps. Tried to charge on low side but wouldn't take a charge. Read revving the engine might help but don't know how that would help. Tech manual I got is Very explicit that it should be charged from the 'high' side?? Of course my r134 hose and gauge won't fit the 'high' side port.

Any help on any of these problems would be greatly appreciated. Thanks in advance.. Rick (Dusty-D)

2001 S-Type 4.0 liter V8
1988 XJ6 (XJ40) in-line 6
2003 Toyota Avalon V6
2003 Chevy Silverado K35001-Ton Crew-cab Dually Duramax 6.6 liter w/Allison 5 speed auto trans
1996 Chevy Tahoe 4WD 350ci
1996 Buick Roadmaster (factory Corvette LT1 engine) 350ci

 

Check fuse in cabin fuse box for OBDII and only recharge freon from LOW side.

 

Flashing check engine light is indicative of a misfire with potential for cat damage, I wouldn't drive it until you can trace the fault.

 

I have BOXES filled with used coils that I got when I worked at the dealer. When I find a bad one I mark it with an X and toss it into the trash.
The X200 4.0 ignition coils were a constant problem (as well as the 3.0). I had a 2001 S-Type 4.0 for a few years and I kept a few spare coils in the boot 'just-in-case'.

For some reason the PTEC does not recognize ignition coil misfires as readily as other model Jaguars. When the misfire becomes constant and for a longer period of time, the PTEC will finally flag a cylinder number.

They are not that pricey because they are also used in the Ford 3.9.

bob

 

Find and correct the misfire(s) as a flashing MIL means catalyst damage is occurring!

Remove the coil units and inspect them for shorting due to oil fouling in the spark plug wells. If oil is present, replace the cam cover gaskets and spark plug boss seals. Oil fouling usually results in the coil unit shorting. They are relatively inexpensive and can be found on eBay or from one of the forum sponsors such as SNG Barratt.

 

Hiya Rick,

Welcome to the forum. Others have addressed the flashing check engine light. That means you've got potential overheating of the cats, so get that fixed first.

AC? Here you go:

Epic troubleshooting guide for the climate control system


Specifically, run the test of the DCCV as detailed in post #2. After that, play with the automatic and manual modes to determine if you should proceed to post #3 or #4.

The 30psi reading you observed makes me think the AC system itself is capable of putting out cold air, but the DCCV is sticking and dumping heat into the cabin. Don't mess with adding refrigerant until you confirm the DCCV is behaving itself.

 

Thank you for two great answers. Don't now why I didn't about a fuse except maybe because the reader came on and went through the scan. Will check the fuse box.

On A/C, I thought Always charge on the low side. The manual I downloaded said 'high' and really caught me off guard. Does revving the engine help with the charge. Doesn't seem to want to take more than 30 pounds with ambient temp over 90 degrees F.

 

Thank you for that advise. I thought maybe a bad plug on the slight miss; the stumble and Not downshifting with the flashing engine light had me really puzzled. It's only done the "flashing" thing once. Am now about 200 miles from home so will stay off gas going up hills as much as I can to get home and find the cause.

 

WOW - Thanks. Hadn't even considered a coil. Is there an easy way to test them if I don't get a specific cylinder code called? Will a spark plug tester show the cylinder? That will be a process putting it on each of the 8 plugs. I feel the miss at both exhaust pipes.

 

COP (Coil On Plug) Tester. Best way to check each coil.

 

Thank you so much. I'm about 200 miles from home so will 'limp home' and do my best Not yo put it under a load so as not to hurt the cat anymore than may be done. I will check all the rest of your advise also as soon as I get home. May put it up on my lift to see if I can see any physical damage to the cat. converter.

 

Thank you. That's great advise that I will follow.
I'll find and fix the miss and stumble first, then follow your detail order of the previous answer.
I appreciate you time to answer. Do have to 'limp home' as I'm 200 miles from home now. The stumble only happened one and I can feel the miss from both pipes.
Excessive heat in converter never entered my mind. Hope I can repair before too much damage is caused. I'm assuming too much heat in converter is a cause of the miss fire.
Thanks for the order list to follow to check and repair.

 

Actually, it's the other way around. The cats "burn off" any unburned fuel in the exhaust. I used quotes, because it's actually a magic catalytic process, not actual combustion. But the cats do generate heat as they work their magic to clean up the exhaust.

However, the cats are physically capable of only handling small amounts of fuel. Dump too much raw fuel in the exhaust, and too much magic occurs, leading to heat-damaged cats, an expensive proposition. That's why the light flashes to get your attention, to say things are going to get spendy real quick if you don't pull over.

I'd be very hesitant to cover 200 miles with cats on the edge of overheating. Before setting out, can you pull any of the coils for inspection? One common problem is oil collecting in the spark plug wells. If so, the proper fix is to clean up the oil and replace the valve cover gaskets. But if the leak rate is slow, you may be able to just sop up that oil as an interim band-aid, and replace the gaskets when you get home.

 

Thank you SO much!! It took me a while, but I read your entire step by step procedure you provided by your link. Absolutely fantastic - what a great job.
This guide on how to start and step through the different tests is invaluable.
I have of course got the two main tools you mentioned in post #1 (actually already had them) and am going through my system step 1 to the end as you advised. Found couple little problems and will continue through the system till All is done.
You did a Great job requiring much time and effort for all to learn.
Thanks again!!!! Rick