P38 4.0 thor lack of power after 2000 rpm and not on all cylinders.?

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JellySpanners

New Member
Posts
71
Location
Gloucester
Totally cheesed off already! Half hours of typing lost and that’s without the stupid log in thing taking 10 attempts...Can’t see me lasting long on here with duff British engineering and all???

Anyway

Been a mechanic for 32 years and against my better judgment bought a Range Rover P38 4.0 HSE Auto. Got it 4 months ago with a smashed front diff, the previous owner had lost faith in it as he had just had a donor engine fitted.

Car starts and runs fine until you get to 2000 rpm where it appears to go very flat and not develop any torque and has a juddery feel like it’s not funning on all cylinders, I have been through everything I know and have searched on here but threads on here seem to go dead when people have fixed theirs then drive off into the sunset?

Here is a list of exactly what I have done to date;

Cats for MOT...Good quality as oe with good flow
Spark Plugs, NGK platinum as recommended
Ht leads, good quality 8mm silicon
Both coil packs replaced with Bosch ones
Auto Gearbox filter and oil changed
Compression test...All range from 155-175psi
Genuine Air Flow Meter fitted and inlet pipe checked
Inlet manifold removed, injectors tested filters cleaned new seals
Fuel pressure and flow tested at idle and under load
Engine ECU removed checked and cleaned connections
Crank sensor removed cleaned and checked and flywheel
Knock sensor checked
Lambda sensors replaced with Bosch oe
Alternator noisy at idle but charging ok

Car has no diag faults showing and EML light doesn’t show, all temps correct and doesn’t use any water or oil and is running on super unleaded?

If anyone can help with this I would be most grateful as I am exhausting my range of ideas

Many thanks in advance
 
Hi,welcome.
Did u reset the adaptive values after removing/replacing sensors?which diag tool did u use?how much voltage are you getting from ur bat?p38 are very very very sensible to voltage,if u suspect ur alternator get a reading from the alternator and c how much it is puting,and check the bat how much is it receiving!
 
JellySpanners said:
Totally cheesed off already! Half hours of typing lost and that’s without the stupid log in thing taking 10 attempts...Can’t see me lasting long on here with duff British engineering and all???

Anyway

Been a mechanic for 32 years and against my better judgment bought a Range Rover P38 4.0 HSE Auto. Got it 4 months ago with a smashed front diff, the previous owner had lost faith in it as he had just had a donor engine fitted.

Car starts and runs fine until you get to 2000 rpm where it appears to go very flat and not develop any torque and has a juddery feel like it’s not funning on all cylinders, I have been through everything I know and have searched on here but threads on here seem to go dead when people have fixed theirs then drive off into the sunset?

Here is a list of exactly what I have done to date;

Cats for MOT...Good quality as oe with good flow
Spark Plugs, NGK platinum as recommended
Ht leads, good quality 8mm silicon
Both coil packs replaced with Bosch ones
Auto Gearbox filter and oil changed
Compression test...All range from 155-175psi
Genuine Air Flow Meter fitted and inlet pipe checked
Inlet manifold removed, injectors tested filters cleaned new seals
Fuel pressure and flow tested at idle and under load
Engine ECU removed checked and cleaned connections
Crank sensor removed cleaned and checked and flywheel
Knock sensor checked
Lambda sensors replaced with Bosch oe
Alternator noisy at idle but charging ok

Car has no diag faults showing and EML light doesn’t show, all temps correct and doesn’t use any water or oil and is running on super unleaded?

If anyone can help with this I would be most grateful as I am exhausting my range of ideas

Many thanks in advance
Click to expand...

:welcome2:You can set the site to log you in automatically every time you visit.

For the rest I would suggest you need to read the fault codes and re-set the adaptive values for starters
If you put your location, there may be someone nearby with Faultmate or Testbook.
 
Hi Guys, Have to admit to only using a Snap on Scanner and I know they only scratch the surface and no havent been able to reset the adaptive values, having said that did have the engine ECU off for over half an hour so was hopeing it may have a re-learn capacity..

I will double check the charging as I know it can cause gearbox faults etc. and I have a new alternator on its way..

Im in the Gloucester area..
 
From your description the fault sounds very much like a low MAF reading.You need to see some live data readings from it,22-25kg/hr at idle and more than 85kg/hr at 3000 rpm engine running free.Less than this and the ecu will only give a small injector pulse width,making the engine run lean and lack power.You say it has a genuine Bosch MAF,there are plenty of fakes around in Bosch boxes - none of them work properly.
If your scanner will read oxy sensors as live data you will probably see that they are staying low at 0v when the engine is struggling.
 
eightinavee said:
From your description the fault sounds very much like a low MAF reading.You need to see some live data readings from it,22-25kg/hr at idle and more than 85kg/hr at 3000 rpm engine running free.Less than this and the ecu will only give a small injector pulse width,making the engine run lean and lack power.You say it has a genuine Bosch MAF,there are plenty of fakes around in Bosch boxes - none of them work properly.
If your scanner will read oxy sensors as live data you will probably see that they are staying low at 0v when the engine is struggling.
Click to expand...

Air flow meter was bought from P38 spares and looks genuine to me but I do think it feels like a lack of fueling, and has to be metering problem? Lambdas are reading between o.oo6 and .750 volts which I recon to be normal and air flow is increasing although its hard driving and using a scanner these days..

I wonder if there is a fixed penalty for driving with a diag ...?
 
Well if you can do live data you are almost home.Look at the Oxy sensor readings when its struggling - bet they are down at 0v,at cruise they will be cycling,0-0.8v up and down - but as soon as you mkae it work for a living they will stay down.
Classic Bosch Motronic with a low reading Maf.
Can you get the wife/mistress/girlfriend/TA/workshop guard dog to drive while you watch the scanner ? ;)
 
eightinavee said:
Well if you can do live data you are almost home.Look at the Oxy sensor readings when its struggling - bet they are down at 0v,at cruise they will be cycling,0-0.8v up and down - but as soon as you mkae it work for a living they will stay down.
Classic Bosch Motronic with a low reading Maf.
Can you get the wife/mistress/girlfriend/TA/workshop guard dog to drive while you watch the scanner ? ;)
Click to expand...

I will see what readings I can get tomorrow, My Black Labrador would help but he isnt that good and barks up the wrong tree sometimes...Pop round a mates garage and borrow one of his blokes ....
 
JellySpanners said:
I will see what readings I can get tomorrow, My Black Labrador would help but he isnt that good and barks up the wrong tree sometimes...Pop round a mates garage and borrow one of his blokes ....
Click to expand...
All black labs are good for is clearing up food spillages and looking good.:D
See if you can get a driver so you can look at the scanner - the Motronic is terrible for needing an accurate airflow reading,the earlier Gems ones were more tolerant of a dodgy Maf.
 
Has the reluctor ring on the flywheel been damaged during the engine swap? I had a similer fault on my 4.6 and it was a duff crank sensor,although i see you have checked it, it could be worth a second look.
 
v8hotrodboy said:
Has the reluctor ring on the flywheel been damaged during the engine swap? I had a similer fault on my 4.6 and it was a duff crank sensor,although i see you have checked it, it could be worth a second look.
Click to expand...

The reluctor looks ok as far as I can see it, I really must scope it, but was thinking if it had any bareing on the fluffy running after seeing the pattern its needs to run properly...It was oily and spaced properly for an auto but I suppose another £50 wont hurt...
 
Ian A said:
what about oil pressure, is there a chance the relief valve is stuck and it's pumping up the lifters.
just a thought.
Click to expand...

Thats what I like about these sites, whan people put their heads together more ideas pop up...Cheers Ian I hadent thought of that one, I know they are a bitch to get oil up if they dry out....Have to get the gauge out...may just bang another filter on for a try too...?
 
Assuming its not a collapsed exhaust silencer creating high backpressure, then I would agree with most of the others about it running weak. You need to read any fault codes in the Bosch EMS ecu, thats how a dealer would diagnose.
To confirm its not engine speed related, with car stationary, raise engine speed above 2000 rpm to say 4000 and see if you getting any running issues (this assumes everytime u drive car above 2000rpm u get the problem, ie its not intermittent ). If not this would suggest the cam/crank sensors are probably ok.
Have a look online for the correct voltage range for the bosch lambda sensor as 0.006 looks way too weak.
The next bit I've done on 14CUX engines, but not on a Thor and its quite safe to do. Run engine with the airflow meter connector disconnected. Ecu will then use throttle pot signal for fueling, take vehicle for test drive & see if engine performance recovers. If no change, reconnect airflow meter and disconnect the throttle pot & take for a drive. If you are planning to take fault code readings do it before you do above tests as these tests will induce fault codes. What fuel pressure did you get (when you had the poor running).
 
davidg said:
Assuming its not a collapsed exhaust silencer creating high backpressure, then I would agree with most of the others about it running weak. You need to read any fault codes in the Bosch EMS ecu, thats how a dealer would diagnose.
To confirm its not engine speed related, with car stationary, raise engine speed above 2000 rpm to say 4000 and see if you getting any running issues (this assumes everytime u drive car above 2000rpm u get the problem, ie its not intermittent ). If not this would suggest the cam/crank sensors are probably ok.
Have a look online for the correct voltage range for the bosch lambda sensor as 0.006 looks way too weak.
The next bit I've done on 14CUX engines, but not on a Thor and its quite safe to do. Run engine with the airflow meter connector disconnected. Ecu will then use throttle pot signal for fueling, take vehicle for test drive & see if engine performance recovers. If no change, reconnect airflow meter and disconnect the throttle pot & take for a drive. If you are planning to take fault code readings do it before you do above tests as these tests will induce fault codes. What fuel pressure did you get (when you had the poor running).
Click to expand...

when the car is stood still you can do what ever you want with the reves and it performs as normal, no missfire or anything, having said that there does seem to be some sort of imballance in the engine around the 4k mark and I remember reading that the thor engine was a legend for being smooth....The fuel pressure under test both at idle and under full load never changed from a static 50psi ish....I cant believe that a 4 liter engime has no fuel filter, Who in their right mind eh...?
 
JellySpanners said:
when the car is stood still you can do what ever you want with the reves and it performs as normal, no missfire or anything, having said that there does seem to be some sort of imballance in the engine around the 4k mark and I remember reading that the thor engine was a legend for being smooth....The fuel pressure under test both at idle and under full load never changed from a static 50psi ish....I cant believe that a 4 liter engime has no fuel filter, Who in their right mind eh...?
Click to expand...

Jelly
Fuel filter is in the fuel tank :D
 
JellySpanners said:
But its not a replacable service item one is it, all I could find was its the gause type on the pump pick up...?
Click to expand...

I dont think it is a service item, i bought stuff to service mine and got a fuel filter (in line type) at the same time, i serviced the car but could not find the filter so left it, i had the drive plate replaced and asked them to change the filter while it was on the ramp, picked up the car and the filter was on the seat, asked why they had not fitted the filter he told me my model filter was in the tank and didn't need changing :confused:
 
Ian A said:
I dont think it is a service item, i bought stuff to service mine and got a fuel filter (in line type) at the same time, i serviced the car but could not find the filter so left it, i had the drive plate replaced and asked them to change the filter while it was on the ramp, picked up the car and the filter was on the seat, asked why they had not fitted the filter he told me my model filter was in the tank and didn't need changing :confused:
Click to expand...

Same here the motor factor gave me the inline filter listed in the book and I searched the car for one, after a google search found that 99 onwards the fuel filter has been left off...I cant believe that a engine with so much through put of fuel hasent got one and relies on just the nylon gause on the pump???

Fair play thor is a bit of a mind blower from a technical point of view?
 
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