I don't recall ever seeing this specific question being answered. It did come up once or twice before but the thread went off in a different direction.

The OBDII reader does show throttle position as % open (100% = WOT).

If the throttle cable has slipped, will the OBDII readout reflect this in that it will not show 100% when pedal is floored?

Seems like it would/should but I've never seen anyone suggest this when cable slip is suspected.

Thanks,
John

 

There were no OBDII codes thrown by my wife's 2006 XK8 when I read about the throttle cable tightening procedure years ago. I checked the cable, found it to have slacked off by several turns over the years, tightened it up as suggested, and the engine's response improved immediately. No codes of any kind before I performed the fix....

 

Oh Jon, I think I confused things. On my OBDII there is a reading called throttle position. It will change from 0% to 100% depending on how pressed down the pedal is.

I am surprised that no one mentions this when discussing possible cable slip. I'm just trying to validate that the readout comes from the throttle itself, therefore if cable has slipped, you'd never see 100%.

John

 

This is curious, no thoughts? Is my OBDII the only one with throttle position display on it?

John

 

No, yours is not! Autoenginuity (and many others) also shows real time throttle position and yes, if the cable is slack, flooring the pedal will only give a reading of less than 100% , depending on the slackness.

 

Thanks Astromorg, I just wanted 2b sure. You have a great weekend.

John

 

As an additional note, there is special procedure from Jaguar to check / set this.
It first let you, with cold engine, take out the slack till the reading starts to go up, then 1/4 turn back.
Then it lets you adjust the accelerator bump stop (a real stop on earlier models, a kick down switch on later ones) at 92% (if memory serves well).
There were cases at the XJ forum where a setting above 95% triggered fault codes.

 

Hi Eric,

If the slip is shown on the OBDII, why look anywhere else?

Maybe folks find the mechanical check easier than the OBDII? I dont know. Part of the reason for my question was that its always seemed so much easier to plug in the reader, but it's never come up before in any of the cable slip discussions.

tell me what you think when you have a chance.
Thanks
John

 

JohnKen,

Before I knew what a OBDII was I had a 1998 XK8, which was underperforming.....I found that the throttle linkage had slipped and was only opening the Flipper about 70% of the way..... even as dumb as I was about the new XK8's, I realized that the Linkage needed adjusting.....So that's what I did, I got a screwdriver and an adjustable wrench and reset it...Amazing thing happened when I started it up and drove down the street....You would think I had Supercharged it.....Full throttle is an amazing thing!

Billy Clyde

 

Thanks Billy,

John

 

I presume it is a left-over from the time that manufacturers went electronic, but customers did not have the tools like OBD2 readers.

People might just take a lucky shot, but I do agree with you that the only scientific way is to read the actual position of the throttle body valve (which is represented by the voltage --> percentage which you read in your reader).

Too much slack in the cable is not really a problem, it will just not allow you to reach the full throttle.
Too tight however will not allow the TB valve to close against its stop, then mixing up the calibration for the fuel maps.