P38 dhse no power but only in reverse?

Stig1 · Feb 2, 2020

Datatek said:
If it revs freely in reverse with fuse 11 fitted, then the problem is not in the gearbox. If it doesn't rev freely there is a gearbox problem.

I've fitted the fuse 11 today and the car revs free when selecting reverse . But I did notice yesterday when putting the car on the ramps in drive it didnt want to move off in drive either very well so I selected lo range and used that to get it on . I'm wondering if what ever it is . Is related to my low mpg

Wazzajnr · Feb 2, 2020

Linings come free of shoes in transmission brake and binding up perhaps?
Drive it around a bit and feel if transmission brake drum is hot.

Datatek · Feb 3, 2020

Wazzajnr said:
Linings come free of shoes in transmission brake and binding up perhaps?
Drive it around a bit and feel if transmission brake drum is hot.

You pinched my next suggestion

Pull the parking brake drum off and take look

Stig1 · Feb 3, 2020

It's looking like my map sensor is faulty as I was told to check pin 1 and it should have around 1.8v and mines only showing 0.5v you think this could be causing my problems

Datatek · Feb 3, 2020

Stig1 said:
It's looking like my map sensor is faulty as I was told to check pin 1 and it should have around 1.8v and mines only showing 0.5v you think this could be causing my problems

It will not make a difference between forward and reverse. Voltage varies with manifold pressure.

Stig1 · Feb 3, 2020

Datatek said:
It will not make a difference between forward and reverse. Voltage varies with manifold pressure.

When putting it on the ramps the weekend I found it not really wanting to pull in drive either

Datatek · Feb 4, 2020

Stig1 said:
When putting it on the ramps the weekend I found it not really wanting to pull in drive either

As we have said, check the parking brake.
It needs to go on diagnostics to determine if the engine is producing power and being mechanically limited, or if it is failing to produce power and to check for any fault codes.

Stig1 · Feb 4, 2020

Datatek said:
As we have said, check the parking brake.
It needs to go on diagnostics to determine if the engine is producing power and being mechanically limited, or if it is failing to produce power and to check for any fault codes.

I have hawkeye and it's not showing any fault codes

Datatek · Feb 4, 2020

Stig1 said:
I have hawkeye and it's not showing any fault codes

But if you look in the right place in live data, it should give an indication of engine power being generated, at least it does with Faultmate. You should also be able to see the throttle pedal position etc to see if the throttle pot is OK.

Wazzajnr · Feb 4, 2020

Datatek said:
But if you look in the right place in live data, it should give an indication of engine power being generated, at least it does with Faultmate. You should also be able to see the throttle pedal position etc to see if the throttle pot is OK.

Probably called "torque demand" or something similar.
You could also hook up a tow rope to another car and see how easy it is to tow it.
My money is still on something mechanical if it revs to 1600rpm foot hard down but revs freely in neutral.

Datatek · Feb 4, 2020

Wazzajnr said:
Probably called "torque demand" or something similar.
You could also hook up a tow rope to another car and see how easy it is to tow it.
My money is still on something mechanical if it revs to 1600rpm foot hard down but revs freely in neutral.

At the moment, my money is on the handbrake.

Henry_b · Feb 4, 2020

park it on a hill in neutral with the handbrake off, engine running of course!!

If the handbrake is on/stuck it will either roll or drag, it should freewheel

..

keep your foot ready for the footbrake though

Rubberknees · Feb 5, 2020

Stig1 said:
I'm still trying to track down the issue with my p38 has plenty power in all forward gears but put it in reverse and it wont even get you up a small kerb stone

Just spotted this post. Does your car have EGR and maf sensor ( the one on air intake next to air filter box) I had similar a few years back. Unplug MAF and see what happens. This should default to pre-set settings, I had a faulty MAF which affected other things (shouldn't do but did) once unplugged ran fine
Its worth a try Stig, only takes a minute

Stig1 · Feb 5, 2020

Rubberknees said:
Just spotted this post. Does your car have EGR and maf sensor ( the one on air intake next to air filter box) I had similar a few years back. Unplug MAF and see what happens. This should default to pre-set settings, I had a faulty MAF which affected other things (shouldn't do but did) once unplugged ran fine
Its worth a try Stig, only takes a minute

yes mines the later one with both egr and maf I'll give it a try thanks

Rubberknees · Feb 5, 2020

Stig1 said:
yes mines the later one with both egr and maf I'll give it a try thanks

would recommend blanking off EGR. Use search bar to find threads on how to do it, its very simple to do

Datatek · Feb 5, 2020

Rubberknees said:
would recommend blanking off EGR. Use search bar to find threads on how to do it, its very simple to do

All that is needed on the P38 is to pull the vacuum pipe of the EGR actuator, block the tube with an M5 screw.
It can then be put back easily for the MOT. No blanking plate needed.

Stig1 · Feb 8, 2020

Henry_b said:
park it on a hill in neutral with the handbrake off, engine running of course!!

If the handbrake is on/stuck it will either roll or drag, it should freewheel ..

keep your foot ready for the footbrake though

Checked it today it's not dragging or holding at all

Henry_b · Feb 8, 2020

Stig1 said:
Checked it today it's not dragging or holding at all

The we can rule that out..

Stig1 · Feb 9, 2020

Bit of a update on this I've found out today it's not only reverse it's also forward as I went to get up a kerb and it would not pull up it at all I had to select low range . Wonder if this is linked to why it feels flat going up hill ? Tried unplugging the MAF and makes no diffrence

Datatek · Feb 9, 2020

Stig1 said:
Bit of a update on this I've found out today it's not only reverse it's also forward as I went to get up a kerb and it would not pull up it at all I had to select low range . Wonder if this is linked to why it feels flat going up hill ? Tried unplugging the MAF and makes no diffrence

Pull the pipe off the inlet manifold and look see if the EGR valve is jammed open.
Check the turbo is working.
You really are tilting at rainbows without diagnostics.

P38 dhse no power but only in reverse?

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