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Throttle potentiometer

 
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gilmore



Joined: 01 Feb 2012
Posts: 101

PostPosted: Wed Dec 27, 2017 9:44 pm    Post subject: Throttle potentiometer Reply with quote

My 50th is still suffering from throttle problems - fast idling when hot, hesitation out of junctions (both only occur when hot), then last Sunday she suffered from loss off power on and off for a couple of miles (I headed home).
Iíve previously replaced both exhaust sensors, cleaned the stepper motor, and checked the air intake for leaks, to no avail. My mechanic says the only other thing he can think of is the throttle potentiometer, but LR donít have any.

Any suggestions folks?
Thanks
Rob
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V8GPC



Joined: 03 Apr 2016
Posts: 164
Location: Manchester

PostPosted: Thu Dec 28, 2017 3:30 pm    Post subject: Reply with quote

Taken from the Nanocom GEMS manual

Fuel temperature: This is the value obtained from the fuel temperature sensor, which is located on the metal fuel rail in-between, the cylinder heads. When the engine has been running and is then stood for a short time, heat escaping from the engine can super heat the fuel trapped in the fuel rail, meaning that when restarting an already hot engine, problems can arise (hot starting problems). Having the fuel temperature information means that the GEMS can compensate for this by increasing the injector opening (pulse) period when the fuel temperature is high. This sensor is treated as failsafe by GEMS with the system substituting a value of 40 degrees centigrade upon detection of its failure.

Maybe the sensor is faulty; its ETC6661

https://www.ebay.co.uk/itm/LAND-ROVER-DISCOVERY-RANGE-ROVER-P38-GEMS-3-9-4-0-4-6-FUEL-TEMP-SENSOR-ETC6661/272887292574?epid=1791499879&hash=item3f8959a29e:g:DHgAAOSwwdtZ4gg0

Not cheap, and may not be the problem. New ones are about £100

http://www.paddockspares.com/etc6661-fuel-temp-sensor.html
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V8GPC



Joined: 03 Apr 2016
Posts: 164
Location: Manchester

PostPosted: Thu Dec 28, 2017 3:38 pm    Post subject: Reply with quote

https://www.ebay.co.uk/itm/P38-ROVER-V8-4-6-LITRE-GEMS-INLET-MANIFOLD-INJECTORS-THROTTLE-HOUSING-HRC2616/182975209705?hash=item2a9a2c20e9:g:h1YAAOSwX3FaOuOh

Maybe worth it for the sensors - you could swap them out until you find the culprit.
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Captainbeaky



Joined: 23 Jan 2014
Posts: 112
Location: Madeira, Portugal

PostPosted: Wed Jan 03, 2018 11:48 pm    Post subject: Reply with quote

Itís best to get the car diagnosed properly - otherwise you can end up changing parts unnecessarily, and perhaps still not find the culprit.

Yes, it could be the fuel temp sensor - but it could also be the wiring!
Change the sensor, and the fault doesnít go away, so you move onto the throttle potentiometer.....

Or it could not be an electrical fault at all.

In a recent case, I was diagnosing a poorly performing VW Golf 1.4 - after changing the failed exhaust sensor, it still wasnít right - especially when hot. If I did not have the diagnostic kit for this car, then I wouldnít have found that the device that selects between hot and cold air into the engine had failed to ďhotĒ, and I had intake temperatures of 80 degrees (itís not a turbo engine!)

Any decent LR specialist will have the kit to interrogate the GEMS, and pinpoint the problem straight away.

It wouldnít be a bad idea to pick up an inlet manifold for the parts though!

Yes, a diagnostic check will cost some money, but after all, you are using a mechanics time and often quite considerable investment in tools, itís quite fair that there should be a charge for this.

At the very least, the resistance values of the sensors can be read by a multimieter from the ECU connectors.

Mike.
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gilmore



Joined: 01 Feb 2012
Posts: 101

PostPosted: Tue Jan 16, 2018 10:32 pm    Post subject: Reply with quote

Sound advice mate.
Looks like sheíll have a trip to an LR dealer unless someone knows a specialist in the midlands. My guy (LR Services in Notts) is at the swapping thing out stage.
Cheers
Rob
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Defender 50th Anniversary Edition GB236
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Captainbeaky



Joined: 23 Jan 2014
Posts: 112
Location: Madeira, Portugal

PostPosted: Tue Jan 16, 2018 10:41 pm    Post subject: Reply with quote

Iím not sure a dealer would be the best place either!
You need to find someone who knows the engine and has the right tools.
Iím surprised that a LR specialist doesnít have the basic diagnostic tools - swapping out parts is an expensive pastime.
_________________
Proprietor of Paradise Engineering in Madeira.
Owner of GB386 50th Defender v8 - being rebuilt.

2013 Honda NC700X
2005 Honda XR250R
2007 Smart ForTwo Turbo.
2010 VW Transporter camper.
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Captainbeaky



Joined: 23 Jan 2014
Posts: 112
Location: Madeira, Portugal

PostPosted: Tue Jan 16, 2018 10:43 pm    Post subject: Reply with quote

Suggest you pop on one of the LR forums, and ask on the P38 threads to see if anyone knows of a good specialist with the diagnostic kit.
_________________
Proprietor of Paradise Engineering in Madeira.
Owner of GB386 50th Defender v8 - being rebuilt.

2013 Honda NC700X
2005 Honda XR250R
2007 Smart ForTwo Turbo.
2010 VW Transporter camper.
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