Hi Gillingham, sorry I did not get back earlier, been on hols! The problem is in the throttle position sensor (TPS). Unfortunately, it is a sealed unit. It is a simple potentiometer with a wiper arm which moves over a surface, graphite, wires, or whatever. The TPS is slotted into the throttle butterfly shaft, the more you put your foot down on the accelerator the bigger the voltage produced. If the wiper arm or the surface becomes worn or dirty there is a drop in voltage output & engine power. Some people have suggested cleaning the surfaces by drilling a hole in the TPS and pouring electrical cleaner in but I would probably drill through all the wires, knowing my luck. It has also been suggested that the shaft of the TPS could float in and out and give unreliable contact. This was probably happening in my case since the electrical output increased with out any gaps or flat spots. A fix using two washers was suggested but I could not understand how this was achieved from the article. I also tried cleaning the connector to the wiring loom which is between the plenum chamber and the inlet manifold with out any benefit. This is when I found the TPS had been discontinued. Quite a few web sites list a TPS but when you try to buy one they are out of stock! The Range Rover & Land Rover main dealers can not do anything with out your R. R. or Landy Vin number & again the part number is discontinued. I was advised to search the scrap yards, but the chance of finding a scrap 1994 Range Rover or Land Rover with a newish TPS would be remote.
Also, you need to know which TPS your engine takes. There are at least 4 TPS used during the period 1987 – 95 which look the same, and three of them have different electrical spec. and are not interchangeable, apparently. The 14CUX Electronic Fuel Injection (EFI) was used 1990 - 95, with an early TPS, having a round three pin connector, wires coloured yellow, red & green, Part no ECT8495. This was changed in 1994/95 to an oval plug, wires brown, green & blue, Part no ERR2263. The electrical specs may have been the same as the earlier one but I am not sure of that and the plug would need changing.
Mine is the earlier ECT8495 so yours will be the same. The back of this TPS has the numbers 215SA & 84925A, LUCAS & date of manufacture on it. The mounting is 35mm between the screws, non-adjustable. The voltage range is 0.083-0.547v throttle closed & 4.7-4.9v throttle open. The yellow wire is the 5v supply from the Electronic /Engine Control Unit, red is the signal & green is ground. I have found a TPS listed on a TVR site.
www.racetechdirect.co.uk Part number E0467. It is listed as: “TVR Rover V8 throttle pot (replacement for the round and oval plug). Will fit Pre-Serp and Serp engines. Will also replace Land Rover part ETC8495 and ERR2263. Offer £167.99 ex VAT. RRP £206.00” No specs are listed so I would ask to see them.
At this point I contacted the Factory to ask them what they do in this situation. They told me they had the TPS I was after, the last one on the shelf. An hour later and £388.92 poorer I had the last ETC8495 in my hand but this was cheaper than installing a new EFI system or converting back to carbs. The first TPS lasted me 23 years, this second one should see out the rest of my driving career with any luck. I did ask the parts chaps what they would do for subsequent owners and though they said they would investigate and get back to me, and despite two further emails from me, I have heard no more.
The 14CUX ECU is adaptive and if an alternative TPS with similar specs is fitted it should adapt to it but I do not know the limits involved. It may be a case of ‘suck it & see’. If you give it a go, some tips. Fitting is easy. Open the near side bonnet and cut the power to the ECU by turning off the red battery cut-off switch behind the driver’s seat. Unscrew the old TPS screws carefully and recover the paper gasket, part no ERR4944. If the new unit does not come with one it can be re-used. The connecter to the wiring loom rests on top of the inlet manifold under the plenum chamber. Installation is the reverse. Go for a 15min. drive to warm things up, revelling in the sound of the V8! On your return, do not turn the engine off but let it tick over for at lease 5mins. If you have fitted an original part you will probably not notice any difference in driving. If it is a non-original part there may be a difference but if the unit adapts, this difference will probably decrease or disappear. If all else fails you can put the old one back and think again. If you give it a go, let me know how you get on, Regards,
