My son just bought a 1997 XJ6R with 74,000 miles. Starts and runs fine. Idles well. Once the throttle gets to a certain point during acceleration the car just dies. Doesn't seem to matter if it's fast throttle opening, like stomping on it or slower applications. We do have a CEL PO411 which I understand is air injection. Upon checking it had a blown fuse. Relaxed the fuse but still had CEL. We also reset the car by touching positive and negative battery cables. Any help would be appreciated.

 

P0411 will not cause your stalling problem. You are correct, that is failure of the air-injection system. I'd reckon your fuse was blown because the air pump has gone bad, a very common failure item. If you don't have an intrusive gov't emissions inspection requirement in your locale, get an OBDII Scanner and clear it when it pops up - you'll get them 2-3 times/mo or more if the air pump is kaput. Makes a faint, high-pitched whine on start-up when it is working properly.

I'm not convinced your battery cable trick clears any OBDII codes. If your fuse fixed the problem, then I believe that particular one will go away on its own after some number of successful starts, but I may be mistaken about that.
OBDII readers can be had short of $20 and are well worth it. If your son totes a smart-phone, look into a Chinese ELM 327 clone $5-$20 and the Torque App $4.95, I think, or Free, but the TorquePro is more than worth the purchase price. If he doesn't have a smartphone, but rather an Apple, there is a similar solution, but I believe he'll have to get a wireless OBDII adapter rather than Bluetooth and I don't believe Torque trucks in Appleware but there is some other App others here could probably name. Alternatively, generic, stand-alone OBDII scanners with a cable can be had from Amazon for

 

I've typed an extra paragraph or two into this on initial posting and an edit attempt. Both promptly disappeared. I have neither the time nor patience to try again. Welcome to the forum, please do an intro post in the new member section and review the guidelines so you can launch yourself toward full membership status.

 

My off-the-cuff guess is a faulty throttle position sensor

Cheers
DD