Puffernutter Posted February 17, 2014 Share Posted February 17, 2014 Range Rover P38 MkII, 4.6 HSE, automatic. After jumping it to start (seem to get a flat battery every few days - must see what's taking the juice!), it revved to 6000rpm (not touching the accelerator) then settled back to a fast idle. I let it warm up then drove off, I accelerated to join the traffic but when I took my foot off the accelerator, nothing happened and I carried on accelerating. Applying the brakes hard and turning off the engine meant I stopped! On restart it was fine, but I always have a delay on releasing the pedal to the revs dying away (cruise control is off). The throttle cable is fine and moves freely, as does the business end at the engine. Could this be the cruise control getting involved when it shouldn't? Is there just a simple linkage I can remove to isolate the cruise control to find out? Cheers Peter Quote Link to comment Share on other sites More sharing options...
pete3000 Posted February 17, 2014 Share Posted February 17, 2014 is there a cable? i thought it was a potentiometer which asks the becm nicely to make the car go faster/slower. I know the kick down switch is just that which holds the gearchange longer. Also the sport/manual button changes the resolution of the pot so the power comes on with less travel of your foot. 10/1 your flat battery is being caused by a mk1 or mk2 alarm rf receiver. you can buy a mk3 for £170 which won't wake the car up every 2 minutes from your 448mhz wireless door bell or you neighbours weather station or baby monitor etc. Pete Quote Link to comment Share on other sites More sharing options...
Puffernutter Posted February 18, 2014 Author Share Posted February 18, 2014 Yes, on this one there is a definite cable between the accelerator pedal and the engine. In fact, when the cruise control is working, I can feel the pedal move, that's what makes me think there must be a physical connection between the cruis control and the accelerator linkage. I'm still new to all this - I used to have a 200TDi Defender - I understood that engine (no ECUs!) Cheers Peter Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted February 18, 2014 Share Posted February 18, 2014 There is a fast-idle control valve, but that can't let enough air through to rev to 6000, it's physically too small a hole (approx. 10mm). It's possible the cruise control linkage managed to get stuck, from memory they're vacuum operated so disabling it is as simple as disconnecting & plugging the pipe. Also possible there's a vacuum leak, split hose, etc. Just think yourself lucky you've got a proper throttle cable, GF's Ibiza is fly-by-wire and that gives entertainment. It once decided to cut power as she was at the end of a slip-road joining a busy dual-carriageway. Oh and it's a job for a midget contortionist to change the pedal! Quote Link to comment Share on other sites More sharing options...
elbekko Posted February 18, 2014 Share Posted February 18, 2014 Sounds like your throttle cable is sticking? Quote Link to comment Share on other sites More sharing options...
Puffernutter Posted February 18, 2014 Author Share Posted February 18, 2014 Throttle cable is free every time that I have tried it, I cannot replicate the fault. What I will do is remove the linkage from the cruise control and see if that is the culprit. Cheers Peter Quote Link to comment Share on other sites More sharing options...
poohbear Posted February 20, 2014 Share Posted February 20, 2014 on a GEMS set-up the cruise is vac controlled (pump is tucked between EAS & bulkhead). Pump drives a cable which attaches next to throttle cable on throttle body. It can easily be disconnected. Dave. Quote Link to comment Share on other sites More sharing options...
Puffernutter Posted February 22, 2014 Author Share Posted February 22, 2014 An update. Removed the cruise control inkage. Still had the problem, although this time I noticed that the accelerator pedal was still partly down, so I guess it's a throttle cable problem! Option 1 will be to remove, clean and oil and option 2 will be to replace. Option 2 is probably best, so does anyone know the part number for a P38 Mk2 throttle cable? (4.6 HSE) Cheers Peter Quote Link to comment Share on other sites More sharing options...
elbekko Posted February 23, 2014 Share Posted February 23, 2014 Is it a GEMS or Bosch? Quote Link to comment Share on other sites More sharing options...
Orgasmic Farmer Posted February 23, 2014 Share Posted February 23, 2014 My defender does this but I very quickly traced it to the throttle pedal stop getting hooked under the HD rubber mat if it moved forward a little! Quote Link to comment Share on other sites More sharing options...
Puffernutter Posted February 24, 2014 Author Share Posted February 24, 2014 It's a GEMS. Looking at the throttle cable, it does have quite a tight turn just after the bulkhead and also 180 degree turn into the linkage on the engine. A new throttle cable I think. Does the ECU have any effect on throttle position that could cause this? The throttle is not fly-by-wire, so I can't see how the ECU could race it up to maximum revs? Cheers Peter Quote Link to comment Share on other sites More sharing options...
elbekko Posted February 24, 2014 Share Posted February 24, 2014 Nope, the ECU only gets a value from the TPS, not the other way around. Only other thing it controls is the idle valve, which as Fridge said has a much too small hole to rev it that high. Quote Link to comment Share on other sites More sharing options...
Puffernutter Posted February 24, 2014 Author Share Posted February 24, 2014 Thanks. Looks like we're down to throttle cable/accelerator pedal than. There is a big return spring on the linkage, so I guess that could be ruled out? Cheers Peter Quote Link to comment Share on other sites More sharing options...
Tanuki Posted February 24, 2014 Share Posted February 24, 2014 Have you ever had engine-earthing issues? I've experienced a case in the past where a high-resistance engine-earth had a portion of the starter-motor current getting from the engine-block to the chassis by way of the throttle cable - causing it to heat and melt inside. The result in no way enhanced the smoothness of throttle-operation or the speed of return-to-idle when you took your foot off. Quote Link to comment Share on other sites More sharing options...
Puffernutter Posted February 24, 2014 Author Share Posted February 24, 2014 I've heard of it, seen it on other cars, but not on a landrover (not yet anyway!) Over the weekend (in the light!) I'll strip out the throttle cable and investigate. Cheers Peter Quote Link to comment Share on other sites More sharing options...
Puffernutter Posted February 24, 2014 Author Share Posted February 24, 2014 More diagnostics tonight. I was playing with a Nanocom and on just turning the engine on, I got the uncontrolled acceleration to around 5,500 to 6,00 revs and it hunts around that area for a few seconds then drops to a fast idle. The throttle sensor (according to Nanocom) is operating OK. I hadn't touched the accelerator pedal at all! What is the stepper motor for on the plenum chamber near the throttle sensor? I think I'll change the throttle cable anyway, it will be one less variable! Is there any benefit in removing the plenum chamber and having a look around? Cheers Peter Quote Link to comment Share on other sites More sharing options...
poohbear Posted February 25, 2014 Share Posted February 25, 2014 The stepper is the Idle Air Control Valve, these do have a tendancy to clog up over time - though this usually shows up as a poor idle, stalling in reverse not the other way round. If you have reset any values using nanocom then you may need to reset your Stored Throttle Closed value, there are threads about this on both this forum and rangerovers.net. Dave. Quote Link to comment Share on other sites More sharing options...
Puffernutter Posted February 25, 2014 Author Share Posted February 25, 2014 Thanks for the input. Idle is OK, reverse is OK and I used the Nanocom as "read only" for the engine - although I did get rid of an SRS warning light (but that's a separate ECU)! Cheers Peter Quote Link to comment Share on other sites More sharing options...
poohbear Posted February 25, 2014 Share Posted February 25, 2014 As long as the stored value is the same as the actual then that shouldn't be your issue. Do you have any air leaks around the intake/plenum? D. Quote Link to comment Share on other sites More sharing options...
Puffernutter Posted March 7, 2014 Author Share Posted March 7, 2014 More info. Flat battery again today Jumped it, didn't touch the pedal, but it raced away again. I have established it isn't the throttle cable and it isn't the cruise control linkage. But, when I went around to the throttle linkage to reduce the revs it was hard round and there was a definite stiff point that I had to move it past before it sprung back. Then it was OK again, you could rev the engine and it would return to idle naturally. So, what is in the plenum chamber and how is the throttle linkage and the stepper motor linked? I know I've been told that the stepper motor should be able to race the engine, but it almost seems that it interferes with the free movement of the throttle (and prevents it returning). But I have no pictures of what is in there! Cheers Peter Quote Link to comment Share on other sites More sharing options...
poohbear Posted March 9, 2014 Share Posted March 9, 2014 Stepper and throttle butterfly have no physical connection, infact idle air control happens outside of main throttle body. Throttle spindle passes right through body into TPS on far side - could be binding somehow in it's bearings but. I would think it more likely to be something in the linkage that the throttle cable works on. D. Quote Link to comment Share on other sites More sharing options...
Puffernutter Posted April 28, 2014 Author Share Posted April 28, 2014 OK, hands up I got it wrong - it was the throttle cable! The red beast and I are one again! (Although it certainly put up a fight when I came to change the cable...) Cheers Peter Quote Link to comment Share on other sites More sharing options...
mickeyw Posted April 30, 2014 Share Posted April 30, 2014 Have you overcome the flat battery issue? A colleague has a '98 P38 4.6. He was having flat battery issues, and went all through thoughts of other local rf signals causing havoc with the immobilser system. The ultimate cause of his problem turned out to be the light between the upper and lower tailgate shut not going out when the tailgates were shut. The lamp unit cannot be seen when the tailgates are shut, so hard to tell that it was on, unless you look when it's pitch dark. It took weeks to figure this one out! The flat battery caused all sorts of other starting/immobilser issues to crop up and distract the diagnostic thought process. Quote Link to comment Share on other sites More sharing options...
Puffernutter Posted April 30, 2014 Author Share Posted April 30, 2014 Not yet, but I'll have a look at your suggestion. It is interesting that when I park the car at home (town centre) the battery will flatten quite quickly, when I park it at the caravan storage area (middle of nowhere) it can go a couple of weeks plus without any issues. That's what leads me to think it might be RF related. Cheers Peter Quote Link to comment Share on other sites More sharing options...
Tanuki Posted April 30, 2014 Share Posted April 30, 2014 The issue of local RF sources continually 'waking up' the BECM [or rather, stopping it from going into sleep-mode] is well known: from memory, LR introduced a later model of receiver that was fitted with better filtering so was less-sensitive to radio sources in the vicinity. Quote Link to comment Share on other sites More sharing options...
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