Regulator vacuum hose blanked off?

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sander74

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Hi, I've just purchased my first RR, ( P38 2.5 DSE), and took it round to my local garage for a quick check by the mechanic. Although very impressed with the general condition he did point out that the ECU had been chipped and the throttle regulator vacuum hose disconnected and blanked off with a screw. He was going to re-connect the hose but decided that it was probably done as part of the chipping process and I should seek advice. Land Rover, understandably, are not willing to offer any advice regarding a chipping issue and suggest I leave as is. The engine does run slightly cooler than normal, temp guage at 10 o'clock rather than 12 and I'm told this is a result of the hose being disconnected. Should I re-connect this hose or are there likely to be unwanted consequences?
Any advice will be much appreciated.
 
your prolly beter leaving it for now, bieng a doozel i wouldnt have the first clue what it is or does but theres a reason its off and without adequate research it'd be foolish to tamper if its running fine!
 
sander74 said:
Hi, I've just purchased my first RR, ( P38 2.5 DSE), and took it round to my local garage for a quick check by the mechanic. Although very impressed with the general condition he did point out that the ECU had been chipped and the throttle regulator vacuum hose disconnected and blanked off with a screw. He was going to re-connect the hose but decided that it was probably done as part of the chipping process and I should seek advice. Land Rover, understandably, are not willing to offer any advice regarding a chipping issue and suggest I leave as is. The engine does run slightly cooler than normal, temp guage at 10 o'clock rather than 12 and I'm told this is a result of the hose being disconnected. Should I re-connect this hose or are there likely to be unwanted consequences?
Any advice will be much appreciated.
Click to expand...

What and where is the throttle regulator vacuum hose? Do you mean the one that goes from the manifold to the MAP sensor located on the fuel filter housing? If it is that one, it is connected on mine and it's also chipped with a PSI Power box:D
 
It's a black hose with a blue stripe which ran as you suggested from the underside of a housing on the manifold to the fuel filter housing. The chipping has been done by the installation of a powerlink box if this helps.
 
Then that pipe is for the MAP (Manifold Absolute Pressure sensor) and should be fitted. It certainly is on mine with a PSI Powerbox. The Powerbox affects the fueling not manifold pressure methinks so the pipe should definately be fitted.
 
Agree with Datatec. Re-fit pipe. (it`s same size as diesel leak-off pipe). Do this without playing with owt else so it`s easy to go back in case of problems. RE temp. readings: does it rise to this level fairly quickly, or take a long time to warm up? (thinking of thermostat stuck open?). Mine`s up to 12`clock in about 1 mile of gentle driving then stays there steady.
 
The MAP sensor pipe must be connected. This measures air pressure within the manifold. In conjunction with the intake air temp sensor which measures charge air temperature, a singal is then sent to the ECU from both to get charge volume/mass and pressure. The ECU then uses this info to increase or decrease fueling as required. Neither the ECU or the PSI unit will know how much fuel to inject for a given air temp/mass/pressure unless it is connected. Cannot see how it is running well as you say.
 
wammers said:
The MAP sensor pipe must be connected. This measures air pressure within the manifold. In conjunction with the intake air temp sensor which measures charge air temperature, a singal is then sent to the ECU from both to get charge volume/mass and pressure. The ECU then uses this info to increase or decrease fueling as required. Neither the ECU or the PSI unit will know how much fuel to inject for a given air temp/mass/pressure unless it is connected. Cannot see how it is running well as you say.
Click to expand...

When I got my DHSE, the pipe was not connected cos it had perished and dropped off. The only obvious difference with it connected was to fuel consumption which reduced after refitting as did the black smoke :D
 
Datatek said:
When I got my DHSE, the pipe was not connected cos it had perished and dropped off. The only obvious difference with it connected was to fuel consumption which reduced after refitting as did the black smoke :D
Click to expand...

That is what you could expect with it disconnected. Differing charge air mass/ volume/ pressures need different amounts of fuel, without the information from the MAP and inlet air temp sensors plus correlated info from other sensors the ECU has to do a bit of guessing.
 
Thanks for all the advice guys. Given how well the car runs I'm not convinced it is the MAP vacuum hose we're talking about. I spoke to a mechanic today who, without seeing it, reckons it is much more likely to be the EGR valve vacuum hose that has been blanked off. Going to take it to my local Land Rover dealership on Wed and have a mechanic stick his head under the bonnet to confirm.
I'll take the opportunity to ask him about the running temp while I'm there.
I did notice the guage get up to the 12 o'clock position on sat when climbing a bit of a hill then went back to sitting just above the blue section again when no longer under strain - I don't think this is a major issue and in fact according to another Land rover forum is quite normal for a RR.
 
sander74 said:
Thanks for all the advice guys. Given how well the car runs I'm not convinced it is the MAP vacuum hose we're talking about. I spoke to a mechanic today who, without seeing it, reckons it is much more likely to be the EGR valve vacuum hose that has been blanked off. Going to take it to my local Land Rover dealership on Wed and have a mechanic stick his head under the bonnet to confirm.
I'll take the opportunity to ask him about the running temp while I'm there.
I did notice the guage get up to the 12 o'clock position on sat when climbing a bit of a hill then went back to sitting just above the blue section again when no longer under strain - I don't think this is a major issue and in fact according to another Land rover forum is quite normal for a RR.
Click to expand...

The EGR vacuum hose is located under the manifold on the end of a steel pipe that is clipped up running from front to back, this vac pipe is not connected to the manifold but to the pipe from the exhauster. (VAC pump). The MAP sensor hose goes directly onto the underneath of the the centre of the manifold and directly to the MAP sensor on the side of the fuel filter.
 
I have been changing my spill off pipes and think i have the same hanging loose line, same gauge as spill off pipe just hanging from the rear section of the inlet manifold and can not see where it connects to, it's not to the MAP because that's already in place.
Any idea where this line connects to please
 
One pipe connects from underneath of manifold to MAP sensor, one pipe runs under manifold from exhauster (vac pump) to EGR regulator on bulkhead. Clipped at backend of manifold. Another pipe goes from that via a clip on fuel filter to EGR valve. So there should be three vac pipes.
 
Although land rover dont have the best technology in the world I personally dont believe in changing an engines pedigree,unless that is, you know better,and if you did you would'nt have bought one in the first place.I myself own a 97 hse 4.6 so what do I know.
 
redkevlar said:
Although land rover dont have the best technology in the world I personally dont believe in changing an engines pedigree,unless that is, you know better,and if you did you would'nt have bought one in the first place.I myself own a 97 hse 4.6 so what do I know.
Click to expand...


What brought that comment up?
 
Last edited:
Well..........that explains what that small hose does that was hanging loose from the sensor on the side of my fuel filter. It just didn't look right being open ended. I'd tried to find a connection for it fumbling around under the inlet manifold without success. After reading the above I had a more determined look deploying a mirror. It was obvious then just to the right side of the oil filter housing under the manifold. I hadn't been able to 'feel' it as it has a raised 3/4 circular moulding around it to presumably protect it from being broken off when the manifold is taken off.

Quickly reconnected. I'm guessing it's been knocked off at an oil filter change as it's draped just round the removable cap. It's been like that since I got the car in June. I can't sense any change to the way the engine performs though I haven't done any longer faster journies yet. The only thing was that tick over was faster on a cold start and even after a few minutes was slightly faster than usual but back to normal after a run.

Thank you for the collective knowledge. I'll update if any performance changes become apparent.
 
Speedex750 said:
Well..........that explains what that small hose does that was hanging loose from the sensor on the side of my fuel filter. It just didn't look right being open ended. I'd tried to find a connection for it fumbling around under the inlet manifold without success. After reading the above I had a more determined look deploying a mirror. It was obvious then just to the right side of the oil filter housing under the manifold. I hadn't been able to 'feel' it as it has a raised 3/4 circular moulding around it to presumably protect it from being broken off when the manifold is taken off.

Quickly reconnected. I'm guessing it's been knocked off at an oil filter change as it's draped just round the removable cap. It's been like that since I got the car in June. I can't sense any change to the way the engine performs though I haven't done any longer faster journies yet. The only thing was that tick over was faster on a cold start and even after a few minutes was slightly faster than usual but back to normal after a run.

Thank you for the collective knowledge. I'll update if any performance changes become apparent.
Click to expand...


It should make a dramatic difference to performance. This sensor detects manifold pressure from turbo and adjusts fuelling via ECU to suit. Check that both connectors are free from obstruction and that pipe is not split or blocked.
 
Wow absolutely buzzing everytime I come on here. I had the same issue with a "floating" vac line. I found the nipple under the intake manifold and connected the line. After reading all your comments I am happy to say it belongs their. Working on your own p38 2.5 auto is learning constantly. Amazing knowledge and insight on here boys .
 
Owned mine for a little over a month
Water pump done, thermo, re-did multiple hoses, oil cooler lines and radiator, crank pulley, full service, vacuum hose diagnoses etc. Etc.

The journey so far
 
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