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Discussion Starter #1
Recently got an LP640, when you turn the ignition on its reading 11.5v and can drop to 10.9v before you start the engine. Battery charger reads 14.1v when fully charged but drops instantly when you turn the ignition on. Car starts fine and reads 14.1v when running but getting some electrical gremlins so going to put a new AGM battery on it anyway. Just wanted to check what other people get when they first turn the key. Will see what state the old battery is in when it comes out.
 

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My 04 has almost identical numbers as described and stays on a tender always. No electrical issues here. It takes a lot of energy to crank things over hence the transient drop in voltage until the engine (and alternator) are running, at which point the voltage should climb back to 13.5+ and stay around there while in use. All that looks perfectly normal to me.
It sounds like your problems may require more than a battery swap to solve.
 

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Discussion Starter #3
My volts drop is just on the ignition not cranking. Taking the car down now to do the battery so will report back. Suspect I will not be that lucky. Thanks.
 

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Does it stay at 14.1V the whole time while driving? If so, that doesn't sound good and could be a bad battery. The charging level should go down over time while driving.
 

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Discussion Starter #5
Sitting at idle it would drop it 13.5v, anyway just back from the garage and a new battery appears to have solved the problems. I was getting a P2121 throttle pedal position issue, which makes the car a nightmare to drive, as the E gear does not know when to engage gears. New battery installed and the volts levels are not much different but all the faults have gone away and did not come back on the drive home... Have kept the old battery to put on test and will report back. It was a BOSCH 70ah/760a lead acid battery that we found in the car, that I have replaced with an AGM of the same spec. The factory spec is 68ah/380a which is not very much for a big car. Drove home like it should.
 

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Hi , I see that you are in Yorkshire----i'm in Dorset

I've been quoted about £800 for a replacement battery on a 2005 murcie roadster , which seems a little ridiculous----that's just for the battery , not the labour .

10 can you give me an idea of how much you paid for your new AGM battery , and what make and model it is

2) do you know what the procedure was , in changing the battery----ie was the battery switch turned off first? / I believe the rear wheel arch needs to be removed ? / any other specialist tools needed ? /procedures to be followed

3) what sort of labour time / cost was involved ?----did you go to a main dealer or a lambo specialist

thanks

path
 

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Discussion Starter #7 (Edited)
£800 OMG! Its just a standard 096 battery, any make will do as long as its AGM and got a good 3/4/5yr warranty. Stock battery is 68ah/380a, Halfords do a 4yr 70ah/760a AGM for £145, in the end my local garage fitted a Yuasa YBX9096 same spec for £144 all inc. mind you this is Yorkshire ;-). On the ramp, doors unlocked, key out, battery switch off, rear wheel off, cover panel off, battery out which is tight, then new battery in. My car is a 2008 LP640, so there is also a huge oil cooler in the way as well. Took photos so will try and post them somehow but its a really simple job and the boys at your local garage would probably love to work on something like this. Hope this helps.
 

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Discussion Starter #8
A few days on with the car back home living on a CTEK battery conditioner and the new battery sits fully charged. What is interesting is when I unlock the car and turn the ignition on, with the old battery the charger would start charging, on the new battery it just sits there still saying fully charged. Will not be driving the car far in winter, so will be some months before I can tell if it's a complete fix. Hope this helps.
 

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Discussion Starter #9
Some days later... So CarbonDan was right, it was not the battery :-(. In fact, having tested the battery that came off the car there was nothing wrong with it...! Still not sure why my fault went away, as it is now back with a vengeance. Check engine light on as soon as you turn the key and comes back after a clear codes reset as soon as you start the engine.... A quick check of the engine found one of the left bank intake manifold vacuum actuators was stuck open (bolt on the universal joint arm was stuck), once I freed that off it made no difference to the codes. I am getting P2121 and P1426. The stuck actuator could be broken, no idea how long it was stuck, other sites suggest an O2 sensor. Car starts and runs even, but there is a huge loss of power, making the car almost unusable. Open to suggestions before I give up and it goes to a main dealer in the spring.... Help...
 

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The P2121 code suggests throttle position sensor 'D' is having problems, specifically an incongruity between sensor D and E, so that would make sense if one of them is sticking. I would investigate that item first and probably replace it all together, shouldn't be too expensive.

The P1426 does the same sort of check between the two cat temps of bank 1 and bank 2 and it's finding a difference there as well, which triggers that CEL. Different positions on the throttle between the two banks could cause different rates of combustion and significantly different exhaust temps per bank. It's not an overtemp issue, it's an issue of the temps being different between the banks. So I think you've pretty well narrowed the problem down to the throttle position sensor or the mechanical actuator itself.
 

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Discussion Starter #11
Thanks for this. Which what and where are Sensors 'D' and 'E'. The stuck pneumatic actuator was the one that controls the lower arm on the left bank as part of the VIS system. I am not overly sure what the VIS system does, other than maybe balance plenum air pressure..? Clearly anything stuck would cause an issue but unsure how to check if they are doing there job or need replacing or if it's the control solenoid valve...?
 

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Sounds like you need the proper Lambo computers to diagnose. Otherwise just shooting in the dark.
 

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Discussion Starter #13
Think that is exactly what I will end up doing. It's winter here in the UK, my nearest dealer is 2 hours away and it would need to go on a trailer. So I have a few weeks to tinker and see if I can find the fault before I give up. With some help from this forum, if I can find it, hopefully it will be helpful to other owners. Having found the stuck actuator, I am trying to get my head round the pneumatic VIS system, if it has a leak, then that might account for everything... Process of elimination.
 

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Discussion Starter #14
Update. So having given up last night, I cleared the fault codes one last time and left the car overnight. Just tried the car now and the faults have stayed gone. No engine light, no fault codes, ran and idled at 950ish. As it warmed up the revs jumped to 1100, stumbled around and then settled but still no fault codes. Waited for the engine to warm up to test the pneumatic actuator valves which only come on when warm, they were not opening at all on either side, once the engine is warm they should open bottom valves on both sides at med revs first then top valves on high revs, to help balance air pressure in the plenum. I did a restart and the valves started working, revs back to normal on idle and valves opening and closing as you rev the engine.... Possibly took time to build up pressure in the system again and a restart to get the control valves back working. Time will tell if this was the fix after all... So far no parts required other than a battery I did not need.
 

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Thanks for this. Which what and where are Sensors 'D' and 'E'. The stuck pneumatic actuator was the one that controls the lower arm on the left bank as part of the VIS system. I am not overly sure what the VIS system does, other than maybe balance plenum air pressure..? Clearly anything stuck would cause an issue but unsure how to check if they are doing there job or need replacing or if it's the control solenoid valve...?
I'm not entirely sure at this point, I was just trying to piece things together based off the very sparsely detailed manual. I think the sensors are attached to the throttle bodies themselves and a check of the parts catalog seemed like you can't buy the sensors separately from the TB assembly. But let's hope your fix worked! Maybe just freeing things up was enough to get them moving normally again.
 

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Discussion Starter #16
Thanks CarbonDan, I had done the same and could not work out where Sensors D & E were, or if there was a D & E on each bank or each throttle body..? Had planned a strip down and clean of all 4 throttle bodies, as that fixed my 3.2 VR6 Audi some years ago, but that only has one. Then having noticed by chance the stuck pneumatic actuator and read up on the VIS system, I figured this could be what is causing the issue. On start up and idle, the LIE is expecting them to be closed and therefore its pressure readings would be wrong on that bank, causing the P2121 and P1426 codes I was getting. I may still have a small leak on the pneumatic system, only time will tell if it looses pressure over time or stays fixed. Car has spent a long time stood, having done less that 6,000m in 10 years, so its a bit of a project. Had a 04 manual before, which I missed, where in the world are you based?
 
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