After getting gas for MY Jag XK8 I got the poor performance reading and the car started to buck and skip.
I went to a garage and got 2 codes and they are

P1111

P1226

They clearecd the code and I drove the car about 90mph in sport and regular mode for 45 miles and now no problem.
What could it be. Could I have gotten bad gas.
No poor performence light is coming on now.
Please emal me dukeofearl56@verizon.net asap as I am leaving for Boston today

 

P1111 is always a good sign. It means OnBoard Monitoring Tests completed.

The possible causes of P1226 are shown in the right hand column:



I have no idea what this 'mechanical guard sensor' means!

However, the MIL would almost certainly have reset within the 45 miles you subsequently drove (the necessary two drive cycles being completed in less than this distance) so you can probably put it down to bad gas or an out-of-range signal to the ECU.

Graham

 

On the earlier cars, the mechanical guard in the throttle body prevents the electronically controlled throttle body from straying too far off course in the event of an electronic failure. It was a safety feature before they had full confidence in the electronic throttle concept.

If the problem recurs, there is likely a problem with the throttle body.

 

We have to assume the TPS wasn't included in their 'full confidence' assessment.

Graham

 

Yes, they definitely missed the forest and were lost in the trees.

The mechanical guard sounds like it was a solution to appease arguing factions of engineers.

 

not only that now i get an engine fault lite on.
i put some addditive in my gas drove 10 miles no help.

 

Your most economical alternative is probably to have your throttle body rebuilt.

 

I called a friend who works on the 1997 Jag XK8 He said it was not the computer but the throttle body and can get a rebuilt one for 450 plus 1 1/2 hour labor.
Do you think that would cure the problem?
I had my computer rebuilt 3 years ago.
Any advice would be appreciated since i am going up to Mass from Florida for top shot MP competition.
Than you all
Dave

 

just by chance I put fuel cleaner in the car and put in a new air filter. the other one was soso not too bad but not good.
Now no engine code and drove 100 miles. any other ideas.
Still going to have it checked out though.
Hey thanks for everyones help

 

I may way off but yesterday I put in a fuel cleaner and today no code.
but could a bad air flter cause this code also?
I am still going to have the throttle body checked.
I just can't figure it out when the cleard the codes it came back and after doing what I did no codes afer 100 miles.
Thanks for your great advice

 

I would just drive it and see if it throws more codes at you. It doesn't sound like there was anything serious happening.

 

now I am begining to wonder if it was just bad gas. but woukd that cause that code number to come on? P1226