tarphenry

tarphenry

Well-Known Member
Hi all, I hope that someone can point me in the right direction. I have a P38 Diesel that has developed a problem .It starts and runs fine in neutral and revs freely. However once in Drive it has no power at all .The box changes up and down ,but the engine is very lethargic . The car will not accelerate and takes ages to get to 30mph. I have changed the fuel filter and checked the tube under the manifiold. My Nanocom shows no fault on the gearbox and the only fault showing on the engine is a low voltage to the immobiliser that will not clear. This fault occured once before ,but cleared before I could investigate I have checked for splits and disconnected pipes and the wastegate on the turbo can be moved. because it is intermittant I feel it must be something failing but what?. Thanks in advance Mick
 
tarphenry said:
Hi all, I hope that someone can point me in the right direction. I have a P38 Diesel that has developed a problem .It starts and runs fine in neutral and revs freely. However once in Drive it has no power at all .The box changes up and down ,but the engine is very lethargic . The car will not accelerate and takes ages to get to 30mph. I have changed the fuel filter and checked the tube under the manifiold. My Nanocom shows no fault on the gearbox and the only fault showing on the engine is a low voltage to the immobiliser that will not clear. This fault occured once before ,but cleared before I could investigate. Thanks in advance Mick
Click to expand...
Have you tried disconnect pipe to MAP and if fitted MAF sensors. One at a time
 
If the car has a MAF, unplug the MAF and see if it improves. A failing MAF can cause loss of power, disconnected the engine runs on defaults. Also, if fitted, check that the EGR valve is closing fully.
 
Datatek said:
If the car has a MAF, unplug the MAF and see if it improves. A failing MAF can cause loss of power, disconnected the engine runs on defaults. Also, if fitted, check that the EGR valve is closing fully.
Click to expand...
Thanks, tomorrows job
 
Hi, I have cleaned the MAF but for some reason I cannot see how it unplugs (Got my stupid head on this morning) but I feel after the clean ,it is slightly better (but not much) I have also disconnected the EGR valve temporarily. I notice that on the NANOCOM (showing no faults) that the boost pressure is showing the same as atmosphere even when I rev the engine.. (I checked that the wastegate is not seized. There is no smoke ,it just seems as though someone has turned the engine down to about 50%. It still drives well and is just slower all round. Any help would be greatly appreciated
 
tarphenry said:
Hi, I have cleaned the MAF but for some reason I cannot see how it unplugs (Got my stupid head on this morning) but I feel after the clean ,it is slightly better (but not much) I have also disconnected the EGR valve temporarily. I notice that on the NANOCOM (showing no faults) that the boost pressure is showing the same as atmosphere even when I rev the engine.. (I checked that the wastegate is not seized. There is no smoke ,it just seems as though someone has turned the engine down to about 50%. It still drives well and is just slower all round. Any help would be greatly appreciated
Click to expand...
If it's an auto, stick it in gear, foot on brake, briefly increase revs to 2000 and watch the boost pressure. If it doesn't increase, either the pipe from the manifold to the MAP sensor or the spigot on the manifold is blocked , or just possibly the sensor is not working. A blockage or split pipe is the most likely.
Look carefully and you will find the latch holding the MAF connector, it doesn't part easily.
 
I have cleared the spigot in the inlet manifold and the MAP sensor. Tested the turbo boost (it struggles to get to 2000 revs) but the boost is119 so it appears that the turbo is functioning I have managed to unplug the MAF and the car is back to normal so I suspect that replacing it is in order thanks again
 
Last edited:
tarphenry said:
I have cleared the spigot in the inlet manifold and the MAP sensor. Tested the turbo boost (it struggles to get to 2000 revs) but the boost is119 so it appears that the turbo is functioning I have managed to unplug the MAF and the car is back to normal so I suspect that replacing it is in order thanks again
Click to expand...
Don't go for the cheap Chinese ones. They don't last more than a few months. Try and find an original from a scrapper. They are often on the bay
 
It seems that mine is an odd one with a round plug . I wonder if it can be fitted with the rectangular plug type and change the plug
 
tarphenry said:
It seems that mine is an odd one with a round plug . I wonder if it can be fitted with the rectangular plug type and change the plug
Click to expand...
Never seen one with anything other than a round plug on the diesel. They are not the same as the petrol, the petrol is hot wire, the diesel is hot film, they are not interchangeable so no, you cannot swap the plug. It will run fine with it unplugged, it will use a little more fuel and may smoke on hard acceleration. It might fail the MOT on emissions.
 
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