I was out of gas, pulled up to 7/11 and they only had regular gas.
I went ahead and put in the regular even though I always use Premium.
I have a 2004 XJ8. It was not running well the 1st quarter of a tank, now the "engine failure light" is on and I limped back home at 30 miles per hour.

I live 3 hours from nearest Jag dealership.

Any suggestions!

I feel so stupid...it would have been better to run out of gas!

Help!

 

It certainly sounds like a link, but I'd bet lots of bucks it is pure coincidence. No way a tank of low octane gas should have any negative effect beyond an occasional knock sensor code. The ECM on these cars will detect any knock from low octane and retard the timing sufficiently to prevent any problems. You may have actually gotten a bad tank of gas with unknown contaminates that could cause those problems, but it has absolutely nothing to do with the grade of gas.

I put regular gas in my 2000 XJ8 every 2nd or 3rd tank, and did that over 120,000 miles with zero detectable problems.

First thing I'd do is take that car to the nearest Autozone or other auto parts store and have them read those codes for you (for free) and then reset them. Make sure you make a note of the codes and look them up online to get an idea what might have triggered the CEL. If it is a big problem, the light will be triggered again very quickly, and then you can decide if you should take it to a local mechanic, try to drive it to the shop or have it towed (depending on what the codes say). Good luck,
Goose

 

Thanks Goose...good advice...will take it to Autozone tomorrow.
My husband says it may be fuel filter..any thoughts?

West Texas

 

Tough to guess when there are so many billions of things on these complicated cars that can trigger the sensors. Certainly contaminated fuels can clog a fuel filter, but that isn't really that common any more. Best wait 'till you have the codes to start guessing. Post them here if you don't know where to look them up - I'm sure lots of members will be willing to check them and offer suggestions.
Goose

 

Yes, smile, nod and say yes dear when your husband makes wild guesses at what might be wrong with the car. Use of low octane fuel won't throw a code or make any difference whatsoever unless you're really getting on the gas. Even then the reduced performance may not be noticeable to the casual driver.

 

Yes, argee with everything here. I would be more concerned with buying gas from 7/11 at any octane rating than any impact from low octane. Buying 7/11 gas has more possibilitiy of some related cause.

Without fault codes from a CEL, you engage in a huge quessing game with hundreds of possibilities. In fact, I'd rather play a real guessing game than guessing on what might have caused a CEL.

With the codes, someone here will be able to help, but even then, some intelligent guessing is going to occur.

 

Thanks for all the input. My Jag is working great!
Prayed over it the next morning...Engine failure light did NOT come on...ran a little rough but made it to Autozone.
They checked the code and it was normal. I put in a $5 bottle of of Lucas Fuel Treatment and topped off with Premium Gasoline. (advice from Jag Tech) Runs as smooth as before!
West Texas

 

Well aside from wasting $5 on the fuel treatment, no harm done!

 

Well, it never hurts, does it. Maybe ^^ is fond of you this week.

Glad it got worked out, and I would say the fuel treatment isn't a waste, perhaps cleaned out some deposits on the injectors or something positive.

Happy days.

 

I like the praying part. I'm going to try that next time. Glad you're back on the road again.

 

I had a rough idle on my 01 XKR and a can of BG44K on a 350 mile trip cured it.