Source and applicable vehicles? This thread is being referenced by many people with different vehicles.

Yes, that's a good point, I couldn't see why JTIS says to do that but it does seem to be a possible way of telling the ECU that 'this voltage coming out of the accelerator pot is WOT'.

Source was PDI for 2004 XK series, page 4. Probably applicable for all 4.2 XK's 2003-2006.

Now does anyone know if doing a hard reset clears the transmission module to relearn (or is this something WDS was needed for). If so, I think it would be wise to do that as if we are readjusting the Throttle Body Cable, and the Kickdown travel limits, we might as well relearn our transmission driving as well since we just "changed" a lot about the car. I also wonder if this wouldn't prevent some of the occasional transmission faults some owners have that show up once or twice a year out of the blue.

Is it possible, then, if the ECU needs to be taught the WOT voltage level that this adjustment to the pot travel WITHOUT retraining the ECU is actually giving 100 % throttle open before the pedal is all the way down?
If, for example, full travel of the pot produces 5V but the ECU was used to seeing a maximum of (say) 4V then adjusting to give the full 5V would mean 100% throttle with the pedal 4/5 the way down.
Does that make sense?

I would caution anyone with an earlier type throttle body thinking about performing this adjustment to first remove the throttle body air intake pipe and visually observe the position of the throttle plate as they adjust the throttle cable.

On my '97 I discovered that if the cable was adjusted so that the drum roller stopped against the throttle body casting nub, e.g. contacted the end stop; the butterfly position was over-center by at least 10-15 degrees and beginning to close up.

Logic would suggest that the drum roller stop would be located at 90' WOT; but in this case 90' WOT throttle was reached about a quarter of an inch BEFORE the cable drum stop contacted the TB. (see the second pic)

With the intake pipe removed from the top of the throttle body, the throttle plate position is easily visible. With the accelerator pedal fully depressed, the butterfly was close to 90 degrees WOT, but not quite. There was about 5 degrees left to open so I decided to tighten up the cable ends.

After setting what I thought was a perfect WOT, I started the car with my Actron OBD reader. While I did get 99% TPS, I also had the cable so tight the butterfly was being held open at idle. So now it became a compromise and I adjusted the cable to allow the butterfly to totally seat at idle, but w/o any slack in the cable.

The result is that upon starting again, the TPS reads 90% when the accelerator pedal is fully depressed. While this is a non-drive-by-wire TB, and I did do a learning reset after reconnecting the battery, I think there is still something I am missing.

As you can see in the first pic, my '97 4.0 throttle cable adjustment is simply two 13mm bolts riding up and down the end fitting of the cable. Pretty straightforward.

Good on you Sam! Have just adjusted my XK8 throttle cable using your video clip as a guide. Great advice.
Graham Barker

2001 Jaguar S Type 4.0 V8

This sounds awesome and I wonder if this can be done on my S Type, I looked around for this cable and adjuster but couldn't find it. Am I looking in the right place or is it all electical??? Please help if anyone knows how to test the throttle cable and adjust to 100%

thanks,


2001 Jaguar S Type 4.0 V8

Hello guys-

Yes, I'm reviving this thread!

I've got a 1997 coupe. My Android-based Torque software, connected at all times to the ECM through a bluetooth adapter at the ODBII port, consistently tells me I'm at about 75% throttle when I've got the pedal to the floor.

So naturally I'm looking into this throttle cable adjustment.

Thing is, this morning I've got the intake tube off and had someone sit in the car and put the pedal to the floor (engine off). The butterfly went just shy of vertical...let's say an estimated throttle percentage of 95 - 97%.

So my cable seems to be correctly adjusted, but the ECM readings only show about 75% when the pedal is at the floor.

Any thoughts on that?

Thanks boys.

Did mine just guessing about a year ago. Then in Jan this year tweaked it from about 97% on up to a full 100% using the same Torque/Android method.

Did you try 'setting' throttle position sensor, or more like 'teaching' it...I think its posted on the forum somewhere, perhaps in this thread?

Key turned to position II, engine off. Press the pedal to the floor slowly, holding it kickdown for like 5 seconds, and repeating it 3 or 5 times.

Turn key off, then try Torque again to see if it is any better.

Thanks Matt,

I did read about that procedure, but it appeared to be for the later, "full drive by wire" cars. Not sure that it applies to my nearly prehistoric (and ridiculously cool) 1997.

If anyone knows, let's hear it!

It would be interesting to try the learning thing (first post on this page) since you're all plumbed in to read % - it can't do any harm.

Since you have both pedal position sensor and a throttle position sensor, they should be the same %, right? Even if your older prehistoric model doesn't have a pedal sensor, the TPS is still electronic, and an education may still be applicable. ?? I dunno, i'm not the most knowledgeable on that particular system.

Having read through this thread, i decided to test my butterfly, and it seems all is not well.

The first picture shows the spring mechanism at rest.

The second one shows the amount of travel it goes through before the butterfly starts to move.

The third pic shows the the amount of opening achieved by the butterfly when the spring mechanism has hit the stop.

I reckon maybe 60% opening of the butterfly.

Even taking the slack out of the throttle cable when attached, will seem to just keep the spring under tension when the throttle is shut, by reducing the amount of movement before it starts to open the butterfly, but it won't move the fully open position.

Is there a way i can make the mechanism start opening the butterfly earlier, without it having to take up all that slack first?

Or is my throttle mechanism shot?

I wasn't sure in my own mind about the actual differences between the early and late model setup for pedal and throttle plate position sensing and have turned to JTIS and Jaguar product training documents to try and make sense of it.

The conclusion has to be that the pedal position learning procedure is only applicable to the later models fitted with an Accelerator Pedal Position (APP) Sensor. Throttle Cable adjustment is applicable to the early models.

LATER MODELS
The ECM monitors the angle of the accelerator pedal through the accelerator pedal position (APP) sensor (circled in red):



This is my RHD vehicle. It's under the opposite side cover on LHD vehicles.

The APP sensor sends a signal to the ECM which is proportional to the angle of the accelerator. The APP sensor is connected to the accelerator pedal via an accelerator cable. The APP reverts to default settings after a battery disconnect and this is why resetting the pedal travel limits is required.

The ECM also monitors the angle of the throttle plate within the Throttle Body Housing through the throttle position (TP) sensor (circled in blue):



The TP sensor sends a voltage to the ECM which is proportional to the angle of the throttle plate. The voltage from the TP sensor increases with the angle of the throttle plate. There are two sensor tracks within the TP sensor.

The later vehicles therefore have two separately located sensors inputting pedal position and throttle plate to the ECU.

EARLY MODELS
The Throttle Body also has an accelerator pedal position (APP) sensor consisting of twin potentiometers which provide separate analogue input signals, proportional to driver demand to the ECM. As a further safety feature the two potentiometers have different input/output characteristics for unique signal identifications and any corrupt signal between the expected outputs will cause the ECM to switch the throttle to limp home mode.

The early models combine sensing of pedal position and throttle plate within the Throttle Body. This is why correct adjustment of the throttle cable is important on these models.

Graham

@Roadhogg

Pic 1 = TPPS (throttle pedal position) this sends a signal to the other side the TPS to open the butterfly, unless it's attached to the engine, you'll never in a month of sundays see it open any further.

You're getting some mechanical movement, but for full control, see the 3rd pic, there's a link lead going into rubber on the lower rhs, this is for the motor that opens and shuts the butterfly, if it isn't plugged in, no full range. Bolt it back in and test, then report back.

Question, is the car showing any signs or problems for you to remove the throttle?

Probably not.

I forgot to mention that before i took things apart the text display was showing "restricted performance".

I couldn't ascertain why because my check engine lights don't work, so i don't know if they would be showing up, and i don't yet have a fault code reader.

I'm still trying to weigh up which make/model fault code reader would be the most likely to work on my 2000, AJ27, XK8.

The AotoEnginuity will have to wait a while, i need something cheaper at the moment.

I gather the AJ27 has the "drive by wire system".

I took the throttle body off with the intake manifold to clean things up, including the centre of the block because my thermo housing had leaked all over it.

Despite the restricted performance message, it didn't seem to be slowing the car down much, although i don't think she was quite as lively as my neighbours 99 XK8.

That explains the lack of butterfly movement

Thanks Sean B

Looks like it's working after all.
I'll test it when it's back on the car.

Strange! Mine must be a LHD to RHD conversion as mine is on the passenger side!!
Or is it normal for it to be on opposite sides, depending whether XK8 or XKR

The APP has to be on the same side of the vehicle as the accelerator pedal. On RHD's, the APP is on the RH and the ECU on the LH:



On LHD vehicles, the APP is on the LH and the ECU is on RH:



Have you been looking at the ECU and not the APP?

Graham

Adjusted my throttle cable over the weekend, it took 4 turns to eliminate mostl the cable play, I decided to leave a very small amount, just to make make sure it would always return to idle. The old girl is much more responsive throughout the whole the range now, even the wife was impressed!
Thanks for the tip.
Regards,
White Bear.