Different types of throttle pots for RV8?
Discussion
Hi
After using Rover Gauge on my V8S to successfully track down throttle pot error code whilst everything else checks out OK, I've now bought 2 replacements. One was the slotted one from the Range Rover classic which just threw constant error codes once fitted and showed a fixed 11% absolute value on the ECU whether pot is twisted or not. I read somewhere that this means its thrown an out of range error. My existing one shows a 0% position on corrected value and 3-4% on absolute, i.e. self-calibration is working.
Measuring the resistances across the 2 replacement ones they are about 5.7 - 5.9 kOhms across the track.
It is about 200ohms from red to yellow or green depending on which one and position of spindle. This rises to 5.8kOhms as the spindle is rotated and vice versa. I replaced it with another one which is the 2 hole, non-slotted type which was off a Land Rover V8 3.9 and this did the same thing.
The apparent faulty one on my car is 4.8kOhms across the track and rises/falls to same when across red to yellow or green depending on spindle position fully rotated or not.
Can anyone with V8S please measure theirs and let me know their ohm readings before I go out and buy a third one?!
By the way symptoms of running are that of faulty pot / faulty wiring to pot which led me to Rover Gauge and this exercise in the first place.
Any help much appreciated.
After using Rover Gauge on my V8S to successfully track down throttle pot error code whilst everything else checks out OK, I've now bought 2 replacements. One was the slotted one from the Range Rover classic which just threw constant error codes once fitted and showed a fixed 11% absolute value on the ECU whether pot is twisted or not. I read somewhere that this means its thrown an out of range error. My existing one shows a 0% position on corrected value and 3-4% on absolute, i.e. self-calibration is working.
Measuring the resistances across the 2 replacement ones they are about 5.7 - 5.9 kOhms across the track.
It is about 200ohms from red to yellow or green depending on which one and position of spindle. This rises to 5.8kOhms as the spindle is rotated and vice versa. I replaced it with another one which is the 2 hole, non-slotted type which was off a Land Rover V8 3.9 and this did the same thing.
The apparent faulty one on my car is 4.8kOhms across the track and rises/falls to same when across red to yellow or green depending on spindle position fully rotated or not.
Can anyone with V8S please measure theirs and let me know their ohm readings before I go out and buy a third one?!
By the way symptoms of running are that of faulty pot / faulty wiring to pot which led me to Rover Gauge and this exercise in the first place.
Any help much appreciated.
Hi
The thing is its doesn't seem to matter what the voltage says measured at the pot/connector as the ECU just reads 11% for any position of the pot. This is what I find so weird. So that's why I was just wondering if anyone else V8S had the same ohms across their pots as these replacements but still had a fully functioning system. Is there any chance with yours you could please just stick a multimeter across the pot track (green + yellow) and then across red + yellow then red + green. No need to twist the pot, just the basic values would be a big help.
cheers
Rob
The thing is its doesn't seem to matter what the voltage says measured at the pot/connector as the ECU just reads 11% for any position of the pot. This is what I find so weird. So that's why I was just wondering if anyone else V8S had the same ohms across their pots as these replacements but still had a fully functioning system. Is there any chance with yours you could please just stick a multimeter across the pot track (green + yellow) and then across red + yellow then red + green. No need to twist the pot, just the basic values would be a big help.
cheers
Rob
Hey graham
Thank you so much for taking the time to come up with this info. But now I'm mystified! Seems there can be a really low tolerance on these things with no apparent problems with function. I will send you an email however to just borrow that spare pot of yours as a final elimination. If this spare works on yours then its all i need to to eliminate the pot.
Thanks again
Rob
Thank you so much for taking the time to come up with this info. But now I'm mystified! Seems there can be a really low tolerance on these things with no apparent problems with function. I will send you an email however to just borrow that spare pot of yours as a final elimination. If this spare works on yours then its all i need to to eliminate the pot.
Thanks again
Rob
Hmm. Interesting. So 2 new pots are open circuit and the old one isn't. That's really weird too. Unless the connections aren't being made properly at the plug with the 2 new ones. I'll check the voltages at the ECU plug with the 2 new ones as suggested. Thanks for that. At least the ECUmate is showing 11% (limp home) the same as the rover gauge one so I know that at least the info I'm getting is right if very strange.
Cheers
Rob
Cheers
Rob
Just a follow up for future information... It seems the TPS gives a reading of 0 volts between red and green, which appears like open circuit to the ECU even though strictly speaking its not. The reason I had problems with the ECU output showing 11% all the time was that once the ECU read this 0 volts at closed throttle then it would remain a 'fault' all through the motion of the TPS and the fault will just not clear.
Therefore to make it operate correctly at the ECU the TPS needs to be set at say 0.2V and only then is the ECU turned on (re-connect the battery) and then the ECU should read the TPS at say 4-5% absolute and self-calibrate to 0% adjusted. Problem I had was the TPS was at 0 volts when fitted so I had to turn it open to create the 0.2V signal which means its default position was not right, which is also now adjusted.
Running issues still exist though! but at least I've eliminated the TPS itself! Here's the logged TPS in action. Nothing weird there I think.
Therefore to make it operate correctly at the ECU the TPS needs to be set at say 0.2V and only then is the ECU turned on (re-connect the battery) and then the ECU should read the TPS at say 4-5% absolute and self-calibrate to 0% adjusted. Problem I had was the TPS was at 0 volts when fitted so I had to turn it open to create the 0.2V signal which means its default position was not right, which is also now adjusted.
Running issues still exist though! but at least I've eliminated the TPS itself! Here's the logged TPS in action. Nothing weird there I think.
hey, yeah knew it should be that voltage range but it just wasn't doing so when new TPS was fitted in place of old one into the screw holes and the ECU error code was throwing me. Anyway, I've got it sorted now anyway.
The graph just shows the TPS position in % terms as the throttle is open and closed against time. It shows the new TPS doing what it should with no apparent drop in signal, although a reading is only taken every 0.5 secs via the logger.
The running issues is something I've been trying to work out for a while. Its v jerky throttle response at low speeds and engine always stutters and tries to stall when trying to drive if started from cold, as if it was flooding the engine. Soon as it hits 50degC the problems recede and it revs smoothly. Had a TVR garage check virtually everything (compression tests, whole ignition system,fuel pressure) and all ok. Their only suggestion left was TPS and/or ECU but I also need to check for air leaks to eliminate that too. Recently there's been periods of flat throttle response too.
To be continued.....
The graph just shows the TPS position in % terms as the throttle is open and closed against time. It shows the new TPS doing what it should with no apparent drop in signal, although a reading is only taken every 0.5 secs via the logger.
The running issues is something I've been trying to work out for a while. Its v jerky throttle response at low speeds and engine always stutters and tries to stall when trying to drive if started from cold, as if it was flooding the engine. Soon as it hits 50degC the problems recede and it revs smoothly. Had a TVR garage check virtually everything (compression tests, whole ignition system,fuel pressure) and all ok. Their only suggestion left was TPS and/or ECU but I also need to check for air leaks to eliminate that too. Recently there's been periods of flat throttle response too.
To be continued.....
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