Throttle pot nightmare
Discussion
Hi all,
I bought a TVR S3 about 6 months ago and it's absolutely fantastic when it goes, but that doesn't seem to be very often.
I have gone through 5 (yes FIVE !!) Throttle pots and done very few miles, this is costing me a fortune. I even tried a Cebra TP (read all the previous reports) which only lasted 2 weeks. All of them go within a couple of weeks and all of them fail in the same way by sending the ECU a message saying I've got my foot to the floor which makes for very interesting driving around town if the car starts at all.
Does anyone out there know why these fail and only fail repeatedly on the TVR. Is it the vibration or is it the heat ??
The car runs fine but park it up and the next time it starts cross your fingers.
I have the gold connector block and read all the previous suggestions but I'm getting v cheesed off. I have disconnected the TP because if I carry on I will depleat the world supply .... Help
I bought a TVR S3 about 6 months ago and it's absolutely fantastic when it goes, but that doesn't seem to be very often.
I have gone through 5 (yes FIVE !!) Throttle pots and done very few miles, this is costing me a fortune. I even tried a Cebra TP (read all the previous reports) which only lasted 2 weeks. All of them go within a couple of weeks and all of them fail in the same way by sending the ECU a message saying I've got my foot to the floor which makes for very interesting driving around town if the car starts at all.
Does anyone out there know why these fail and only fail repeatedly on the TVR. Is it the vibration or is it the heat ??
The car runs fine but park it up and the next time it starts cross your fingers.
I have the gold connector block and read all the previous suggestions but I'm getting v cheesed off. I have disconnected the TP because if I carry on I will depleat the world supply .... Help
I've had the same experience and went through 3 in less than 4 months last year. Latest pot seems to be holding up OK. I also have the gold wiring etc. but they seem to fail too frequently.
It's an expensive hobby - I remember driving with it unconnected for a long time last year as I couldn't face giving Henry another £45.
Darren
It's an expensive hobby - I remember driving with it unconnected for a long time last year as I couldn't face giving Henry another £45.
Darren
Hoover33 said:
With the TP going so many times..... I wonder if there is another cause to the problem.
Agree, I would be looking at the wider issue. I never had any grief from the TP when I had a S3, but isnt it just a VR, are they sub standard in quality ? are you able to return any TP's you have under warranty, if there faulty ?
Good luck in finding a soloution.
Hi,
Thanks for the suggestions. I agree there must be a reason why all these Throttle pots only survive a matter of weeks. They are genuine ford articles which unfortunately do not come with a warranty.
I have taken the car to a local garage which seem to have a lot of experience with these engines. They have run diagnostics on the ECU several times only to find no fault reported.
I will try fitting one of the old pots to see if that one now works but I'm not holding out much hope
I still feel that there must be a reason so many fail only with TVR's. My suspicion is that when the car is hot and the engine stopped there is a build-up of heat which damages the Throttle pot. This fits all the symptoms ...the car runs fine, Park it up for a few hours /over night, the next time the car is run it's knackered
>> Edited by ChrisGadd on Tuesday 1st March 09:59
Thanks for the suggestions. I agree there must be a reason why all these Throttle pots only survive a matter of weeks. They are genuine ford articles which unfortunately do not come with a warranty.
I have taken the car to a local garage which seem to have a lot of experience with these engines. They have run diagnostics on the ECU several times only to find no fault reported.
I will try fitting one of the old pots to see if that one now works but I'm not holding out much hope
I still feel that there must be a reason so many fail only with TVR's. My suspicion is that when the car is hot and the engine stopped there is a build-up of heat which damages the Throttle pot. This fits all the symptoms ...the car runs fine, Park it up for a few hours /over night, the next time the car is run it's knackered
>> Edited by ChrisGadd on Tuesday 1st March 09:59
Hi Chris.
This story sounds a b***dy nightmare.
I can't believe so many have gone in such a short time without a cause elsewhere and if you are not getting any faults stored on the ECU its hard to know where to look.
I had a similar problem about nine months ago but it took more than changing my TP to get it sorted.
The front wiring loom was very shabby and brittle having cooked on top of the engine for years and I hunted around breakers to find a replacement.
Once I found the right one with the correct injector connections,I took it home and stripped it back to individual wires to check all were flexible and well insulated.Then rebound them so I had maximum length on all and they were as tidy as possible.
When I connected all up again I run all the replacement cables over the top of the coil to keep them away from the block,and put a home made cover over the new TP to keep any water off it from dripping down from the bonet air intake.
This has worked...(touch wood) and I have had no more problems and no more TPs.
The wiring loom stays cool at all times and the TP dry and dependable. New looms are available from Ford if you don't want to chase around the breakers.
Hope this might help.
This story sounds a b***dy nightmare.
I can't believe so many have gone in such a short time without a cause elsewhere and if you are not getting any faults stored on the ECU its hard to know where to look.
I had a similar problem about nine months ago but it took more than changing my TP to get it sorted.
The front wiring loom was very shabby and brittle having cooked on top of the engine for years and I hunted around breakers to find a replacement.
Once I found the right one with the correct injector connections,I took it home and stripped it back to individual wires to check all were flexible and well insulated.Then rebound them so I had maximum length on all and they were as tidy as possible.
When I connected all up again I run all the replacement cables over the top of the coil to keep them away from the block,and put a home made cover over the new TP to keep any water off it from dripping down from the bonet air intake.
This has worked...(touch wood) and I have had no more problems and no more TPs.
The wiring loom stays cool at all times and the TP dry and dependable. New looms are available from Ford if you don't want to chase around the breakers.
Hope this might help.
Thanks Tim,
Sounds like a lot of work, but if all else fails I might have to go down the same route. I have already had a new gold connector fitted without correcting the problem.
I'm still unsure why these Throttle pots fail.
Can they be damaged through a fault in the wiring ?
Has anyone opened one up and worked out why they fail ?
Are there any cleaver people out there who definately know the answer to this long standing costly and very frustrating problem ?
Sounds like a lot of work, but if all else fails I might have to go down the same route. I have already had a new gold connector fitted without correcting the problem.
I'm still unsure why these Throttle pots fail. Can they be damaged through a fault in the wiring ?
Has anyone opened one up and worked out why they fail ?
Are there any cleaver people out there who definately know the answer to this long standing costly and very frustrating problem ?
Hi again Chris.
I am not the one to answer about what is the problem with the S series TPs having never tested or stripped one,but I can say that when mine went the situation could not be remedied until the replacement loom was installed when the new TP and front loom together rectified the problems.
Neither gave a solution on there own but in conjunction have sorted it out,I think long term.
(Still touching wood!)
If your TP is repeatedly failing I would consider going for a new front wiring loom as changes in the current in an old 'cooked' one will undoubtedly have an effect on the stability of electrical currents somewhere and as we know the TP is the first thing to repeatedly give fault.
This problem would also explain why you did not find a fault recorded when interogating the ECU, ...neither did I.
Check out a price from Ford,it might not be so bad, and its simple to replace the old one unplugging each connection at a time and replacing with the new one.
If it gives you peace of mind that it is going to start every time then what is a good price?
Otherwise,go the breakers route,its not impossible.
My thoughts, for what they are worth.I can't guarantee success but it sounds the same problem to me.
I am not the one to answer about what is the problem with the S series TPs having never tested or stripped one,but I can say that when mine went the situation could not be remedied until the replacement loom was installed when the new TP and front loom together rectified the problems.
Neither gave a solution on there own but in conjunction have sorted it out,I think long term.
(Still touching wood!)
If your TP is repeatedly failing I would consider going for a new front wiring loom as changes in the current in an old 'cooked' one will undoubtedly have an effect on the stability of electrical currents somewhere and as we know the TP is the first thing to repeatedly give fault.
This problem would also explain why you did not find a fault recorded when interogating the ECU, ...neither did I.
Check out a price from Ford,it might not be so bad, and its simple to replace the old one unplugging each connection at a time and replacing with the new one.
If it gives you peace of mind that it is going to start every time then what is a good price?
Otherwise,go the breakers route,its not impossible.
My thoughts, for what they are worth.I can't guarantee success but it sounds the same problem to me.
www.interford.co.uk (go to the Sierra forum) is a useful site for 2.9 V6 engine 'funnies'. A lot of knowledgeable guys there.
There are a number of posts on there which suggests the gold plated loom should only be used with the gold plated throttle pot and the tin loom only used with the tin TP. Something to do with the interaction of these metals lousing up the TP output to the ECU.
You say the ECU thinks that the throttle is open when it is actually shut. By this, do you mean that the car is running very rich with a higher than normal tickover ?
The EEC-IV trips into a default mode (Limited Operation Strategy) when it gets confused or receives gibberish from one of its 'critical' sensors' LOS mode sets the mixture to be very rich, rather like driving with the choke on all the time. It may not be the TP that is responsible for this.
Mine had similar symptoms to yours and it turned out to be a build up of oily gunk on the top air flow meter sensor wire. Both AFMs have heated wires but AFAIK its only the top one (white connector / the one with most wires) that reports back to the ECU. May be worth removing the air filter and checking the wire and its housing is clean (use carb cleaner and a cotton bud). This may not be the problem but worth trying before donating another £50 to Frauds.
Other sensors worth checking are the Idle Speed Control Valve (can be cleaned) and the Engine Coolant Sensor - both can result in over rich mixture setting if they start playing up.
>> Edited by SotonS2 on Monday 7th March 12:52
>> Edited by SotonS2 on Monday 7th March 12:55
There are a number of posts on there which suggests the gold plated loom should only be used with the gold plated throttle pot and the tin loom only used with the tin TP. Something to do with the interaction of these metals lousing up the TP output to the ECU.
You say the ECU thinks that the throttle is open when it is actually shut. By this, do you mean that the car is running very rich with a higher than normal tickover ?
The EEC-IV trips into a default mode (Limited Operation Strategy) when it gets confused or receives gibberish from one of its 'critical' sensors' LOS mode sets the mixture to be very rich, rather like driving with the choke on all the time. It may not be the TP that is responsible for this.
Mine had similar symptoms to yours and it turned out to be a build up of oily gunk on the top air flow meter sensor wire. Both AFMs have heated wires but AFAIK its only the top one (white connector / the one with most wires) that reports back to the ECU. May be worth removing the air filter and checking the wire and its housing is clean (use carb cleaner and a cotton bud). This may not be the problem but worth trying before donating another £50 to Frauds.
Other sensors worth checking are the Idle Speed Control Valve (can be cleaned) and the Engine Coolant Sensor - both can result in over rich mixture setting if they start playing up.
>> Edited by SotonS2 on Monday 7th March 12:52
>> Edited by SotonS2 on Monday 7th March 12:55
Hi,
Thanks for the advice about the other sensors. It's definately a TP failure because as soon as it's disconnected the engine runs fine although a little high on tickover.
The symptoms are :-
1) The car uses loads more fuel
2) The engine idles at about 900 rpm but hunts until it stalls.
3) The engine is difficult to start.
4) When tested at the garage the output is a constant 5 volts.
Thanks for the advice about the other sensors. It's definately a TP failure because as soon as it's disconnected the engine runs fine although a little high on tickover.
The symptoms are :-
1) The car uses loads more fuel
2) The engine idles at about 900 rpm but hunts until it stalls.
3) The engine is difficult to start.
4) When tested at the garage the output is a constant 5 volts.
Hi Chris,
The symptoms you describe are indicative of the ECU switching into LOS (get you home) mode which it would do if the TP was either giving out garbage or if you disconnected it altogether - higher tickover, running rich, higher fuel consumption etc.
It seems unlikely that all of the TPs have suffered the same type of failure - straight short, see below. Generally, it seems to be the internals that fail at certain throttle positions, hence the hesitant and stuttering performance that is experienced at fixed throttle position.
A 5v constant output from the centre pin (thanks to chris_chim for putting me straight on that one !) suggests a straight short between the supply and signal return wires (the output should never actually reach 5v, more like 4.6v-4.8v). This short could either be in the loom or in the TP itself. If you like, you could post me a couple of pots and I can check them out. If it transpires that any of them are OK, then at least its one less thing to be chasing when fault finding. Mail me through my profile and I'll send you my address if you want to do this.
The symptoms you describe are indicative of the ECU switching into LOS (get you home) mode which it would do if the TP was either giving out garbage or if you disconnected it altogether - higher tickover, running rich, higher fuel consumption etc.
It seems unlikely that all of the TPs have suffered the same type of failure - straight short, see below. Generally, it seems to be the internals that fail at certain throttle positions, hence the hesitant and stuttering performance that is experienced at fixed throttle position.
A 5v constant output from the centre pin (thanks to chris_chim for putting me straight on that one !) suggests a straight short between the supply and signal return wires (the output should never actually reach 5v, more like 4.6v-4.8v). This short could either be in the loom or in the TP itself. If you like, you could post me a couple of pots and I can check them out. If it transpires that any of them are OK, then at least its one less thing to be chasing when fault finding. Mail me through my profile and I'll send you my address if you want to do this.
But...if its the entire front loom that covers all sensors,including TP,as well as injectors,then its speak to your local Ford dealer,or scrappy.
I would take up Neils offer to get some of your old TPs tested on another loom to establish if they are all mullered.If they are,then I think it is likely to be more than just the replacement TP three wire kit.
That means investing in a replacement front loom when you know you have it licked.
I would take up Neils offer to get some of your old TPs tested on another loom to establish if they are all mullered.If they are,then I think it is likely to be more than just the replacement TP three wire kit.
That means investing in a replacement front loom when you know you have it licked.
Hi everyone. I've got so much help from reading posts on PH over the last four years that it's time for me to give something back to the group.
I too have experienced idling issues. Starts up fine, sometimes, sometimes not, but after a bit of a run when I stop the revs will not return. Occasionally, if I blip the throttle they will drop down, or if I leave it for a minute or so they will return. Sometimes a little too low though.
It gets worse with time. Coupled, eventually, with sporadic acceleration issues.
After cleaning sensors, checking for air leaks, fuel pressure, replacing temp sendor and idle control valve, I borrowed a diagnostic tool from a kind club member. It showed the throttle position sensor as an issue. I replaced it and all was well.
Two years later I'm having the same idling issues starting and I read that it's actually a common problem with the 'S'. Seems odd that no other cars which use the same TPS have this issue so before replacing again I investigated further. Apparently, the electrical side of a TPS rarely fails. It is the return spring which goes. This makes sense when you think about how the revs return after a minute if the spring had become gunked up somehow. I know they are a sealed unit but they are not air or water tight.
After removing the idle control valve for ease of access I removed the TPS to check it. With a good fitting screwdriver so as not to damage the plastic on which the 'd' rod insert I turned it and let go. It returned to position with no sticking what so ever. For precaution I drowned it in isopropyl alchohol and put it back on.
I then followed the rod to the other side of the engine where it connects to the throttle linkage which has two large springs and a plate with a dog-leg slit cut into it, in which a guide roller runs. With my hand I actuated the mechanism, which all looked clean, engine off, and sure enough I felt and heard grating (grit) and it was sticking.
White spirit, cotton buds and kitchen roll was used to drown and clean the springs, roller and back and cut-out of the plate. I have never seen so much solid black grease and grit come from anything before. I guarantee that I would have greased it at the same time as fitting the TPS two years ago and it has taken this long to become full of gunk again. So there is every chance that the original TPS was okay but the action of me greasing sorted it temporarily. Once fully cleaned, the mechanism actuated beautifully. I have not re-greased it at all.
The car now comes back to idle perfectly again, but what I have also found is that it has cured another issue I had. I was about to have the gearbox stripped as the gears won't engage unless you let the revs drop for quite an amount of time and even then it wasn't the best. But now that the roller and springs are free the revs drop quickly when the clutch is depressed and I have a properly working gearbox. I was stunned when I realized this but it was noticable instantly.
Hopefully this will save you time and money and if your problem does turn out to be something else then I wish you well and you've not lost anything in checking this.
Best regards.
I too have experienced idling issues. Starts up fine, sometimes, sometimes not, but after a bit of a run when I stop the revs will not return. Occasionally, if I blip the throttle they will drop down, or if I leave it for a minute or so they will return. Sometimes a little too low though.
It gets worse with time. Coupled, eventually, with sporadic acceleration issues.
After cleaning sensors, checking for air leaks, fuel pressure, replacing temp sendor and idle control valve, I borrowed a diagnostic tool from a kind club member. It showed the throttle position sensor as an issue. I replaced it and all was well.
Two years later I'm having the same idling issues starting and I read that it's actually a common problem with the 'S'. Seems odd that no other cars which use the same TPS have this issue so before replacing again I investigated further. Apparently, the electrical side of a TPS rarely fails. It is the return spring which goes. This makes sense when you think about how the revs return after a minute if the spring had become gunked up somehow. I know they are a sealed unit but they are not air or water tight.
After removing the idle control valve for ease of access I removed the TPS to check it. With a good fitting screwdriver so as not to damage the plastic on which the 'd' rod insert I turned it and let go. It returned to position with no sticking what so ever. For precaution I drowned it in isopropyl alchohol and put it back on.
I then followed the rod to the other side of the engine where it connects to the throttle linkage which has two large springs and a plate with a dog-leg slit cut into it, in which a guide roller runs. With my hand I actuated the mechanism, which all looked clean, engine off, and sure enough I felt and heard grating (grit) and it was sticking.
White spirit, cotton buds and kitchen roll was used to drown and clean the springs, roller and back and cut-out of the plate. I have never seen so much solid black grease and grit come from anything before. I guarantee that I would have greased it at the same time as fitting the TPS two years ago and it has taken this long to become full of gunk again. So there is every chance that the original TPS was okay but the action of me greasing sorted it temporarily. Once fully cleaned, the mechanism actuated beautifully. I have not re-greased it at all.
The car now comes back to idle perfectly again, but what I have also found is that it has cured another issue I had. I was about to have the gearbox stripped as the gears won't engage unless you let the revs drop for quite an amount of time and even then it wasn't the best. But now that the roller and springs are free the revs drop quickly when the clutch is depressed and I have a properly working gearbox. I was stunned when I realized this but it was noticable instantly.
Hopefully this will save you time and money and if your problem does turn out to be something else then I wish you well and you've not lost anything in checking this.
Best regards.
Haven't read all the replies/help but I eventually found a break in the wiring from the TP to the loom which sent me through several throttle pots when they weren't actually at fault. When I discovered the wiring fault it was a ureka moment. It wasn't visible to the eye but electrically night and day when the wiring was moved
hope of some help
John
hope of some help
John
Gassing Station | S Series | Top of Page | What's New | My Stuff