Unable to hold consistent speed/mph
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Senior Member
Joined: Jul 2015
Posts: 101
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From: Delaware, OH
Unable to hold consistent speed/mph
Long-time lurker, but my 1st post!
'97 XJ6 - I'm unable to hold a consistent mph especially at lower speeds like in neighborhoods, parking lots, etc. (i.e. 15mph-35mph) The pedal will allow me to either accel or decel but holding a consistent speed is impossible. I was thinking maybe a bad TPS?
No CELs, or other issues. Thanks for your help!
Dan
'97 XJ6 - I'm unable to hold a consistent mph especially at lower speeds like in neighborhoods, parking lots, etc. (i.e. 15mph-35mph) The pedal will allow me to either accel or decel but holding a consistent speed is impossible. I was thinking maybe a bad TPS?
No CELs, or other issues. Thanks for your help!
Dan
Joined: Feb 2010
Posts: 28,810
Likes: 11,280
From: Adelaide Stralia
Welcome.
When time permits, please do an intro in the "New members area".
If the pedal is "stiff" to operate, then maybe the return spring inside the capstan has bound up. There was a TSB about this a looooong time ago, and I cannot find it quickly.
The TPS does get oil contaminated, thanks to gravity. Regular cleaning of the throttle body and disc, reduces this heaps.
Cleaning thatTPS works, mine did, some report total failure. It is not easy to remove, oil filter off generally helps for access.
When time permits, please do an intro in the "New members area".
If the pedal is "stiff" to operate, then maybe the return spring inside the capstan has bound up. There was a TSB about this a looooong time ago, and I cannot find it quickly.
The TPS does get oil contaminated, thanks to gravity. Regular cleaning of the throttle body and disc, reduces this heaps.
Cleaning thatTPS works, mine did, some report total failure. It is not easy to remove, oil filter off generally helps for access.
Bob names the TSB's in post #4 here: https://www.jaguarforums.com/forum/x...96-xjr-107975/
If you have the trouble of it not returning to idle, here's a no-cost fix and you don't have to wait for parts to arrive in the mail: https://www.jaguarforums.com/forum/x...carman-111454/
If you have the trouble of it not returning to idle, here's a no-cost fix and you don't have to wait for parts to arrive in the mail: https://www.jaguarforums.com/forum/x...carman-111454/
Thread Starter
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Senior Member
Joined: Jul 2015
Posts: 101
Likes: 27
From: Delaware, OH
Appreciate the replies! The throttle is not "stiff" to operate, nor does the idle hang. I'm assuming the TPS on the Jag is basically a rheostat like on most, and it seems there's a 'dead spot'.
Even the cruise has a problem holding a constant speed, especially on down-hills. It lets WAY off on the throttle, then speeds up WAY to much, and repeats this until the ground levels out. Same issue I have when trying to hold a constant slow speed in neighborhoods and such. I can either speed up or slow down with the throttle, but can't hold any given speed. It's quite annoying, especially for any passengers in the old girl.
Even the cruise has a problem holding a constant speed, especially on down-hills. It lets WAY off on the throttle, then speeds up WAY to much, and repeats this until the ground levels out. Same issue I have when trying to hold a constant slow speed in neighborhoods and such. I can either speed up or slow down with the throttle, but can't hold any given speed. It's quite annoying, especially for any passengers in the old girl.
Joined: Feb 2010
Posts: 28,810
Likes: 11,280
From: Adelaide Stralia
OK.
That does sound like TPS to me. Off with the oil filter, out with the 2 retaining screws, spray with Contact Cleaner so it actually gets inside the TPS, work the spindle, spray some more, work it some more, etc.
DO NOT turn ON the ignition with the TPS unplugged. That will confuse the system, and a Dealer Orientation may be needed, which = $$.
Connect an OHM meter and take note of before cleaning numbers across the scale, and during clenaing, and see if that dead spot clears up.
However, you guys got EGR, we did not, and I read on here that this EGR system reeks havoc, mainly with idle, so maybe just a thought.
That does sound like TPS to me. Off with the oil filter, out with the 2 retaining screws, spray with Contact Cleaner so it actually gets inside the TPS, work the spindle, spray some more, work it some more, etc.
DO NOT turn ON the ignition with the TPS unplugged. That will confuse the system, and a Dealer Orientation may be needed, which = $$.
Connect an OHM meter and take note of before cleaning numbers across the scale, and during clenaing, and see if that dead spot clears up.
However, you guys got EGR, we did not, and I read on here that this EGR system reeks havoc, mainly with idle, so maybe just a thought.
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