P38 Turbo power loss

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dubloman

Member
Posts
78
Location
UK
I am sorry if this has been covered before but I can't find any link that covers what is happening to my P38.

It is the Diesel M51 BMW engine none egr and I will explain the problem I have

If I drive normally the car drove fine, then I found that the air in pipe to the turbo had come off and was on and off so not sat firmly on the turbo and gave intermittent issues.

We refitted the pipe (it did have oil within the pipes) I know this is normal but have not yet removed the intercooler pipes etc to clean it, but I will explain more to give the full picture.

The car lost power whilst on a trip to Taunton from Lancashire, I called out my breakdown service as I thought the air intake pipe had popped off the turbo again and needed refitting, they turned up to find that the pipe was secure (I had no tools with me so could not fix it myself) but when we checked the pipe was in place and we discovered that the pipe from the intercooler to the inlet manifold (ally type) was failing and sucking in on itself, this was on Easter Sunday (I was lucky that a very kind 2nd hand parts supplier who I use had one available for me to collect) I nursed the car to him, fitted it, the car was a bit better (I could get home) but still failed.

I have now purchased a new pipe but when I fitted it and tested the car it is still losing power.

To explain how the power loss effects the car, when you put your foot down to overtake on the motorway, it just drops the power out completely, if I build up the power/speed it will reach any speed I want

The issue is the loss of power that you need in overtaking.

If I keep the revs below 3000 rpm (this can go to 3750 in lower gears and lower speeds) but if I take it above it feels like it bogs and when the revs drop to about 2000/2225 then you get acceleration back. If you stay below 3000 rpm then it will pull and pull but over that (it's linked to gear changes as well)

I know it is a weird one as if you sit and rev the car it will go to 4000 to 4500 before it pops, and we back off the revs, but I cannot see any of the pipes collapse under the vacuum, but I am not saying it is not. The pipe I replaced is fine, the vacuum being created would suggest that the turbo is working (unless I am missing something) Could oil in the system be causing this problem and a simple clean would fix the problem or is there something else. Could it have anything to do with the turbo solenoid boost control valve or the other pipes from the turbo to the intercooler?

Any comments or fixes are appreciated and if we can get the vehicle back on the road pulling the way it should I will be grateful

Thanks in advance
Dave
 
Check MAP pipe from inlet manifold to fuel filter is good.

Other turbo pipe might be delaminated inside and blocking under load.

Flush intercooler while you're at it as it should be done regularly.

Might be worth checking the lift pump is working as it should too. There's a How To by Wammers in the Technical Section.

Is this the auto? The autobox is up to the level?
 
If the map pipe is all good, pull the pipe off and try the car if there is no difference I would say the map sensor is shot
 
Thanks, I will check the suggestions tomorrow and report my findings

I had intended to do the intercooler but what is the best solution to flush the intercooler rad?

Thanks
 
Does the engine warning light flash when the power drops?
Check the spigot in the manifold where the MAP pipe fits is not blocked.
Check the fuel filter for contamination.
Check the lift pump is working.
Check the turbo waste gate is not sticking.
Get it on diagnostics.
 
I had the same problem a week or so ago, search running out of get up and go posted by me. I checked all the suggested pipes, ThenI went back to basics, changed fuel and air filter and no problem since, touch wood. Posted on April 15th
 
Datatek said:
Does the engine warning light flash when the power drops?
Check the spigot in the manifold where the MAP pipe fits is not blocked.
Check the fuel filter for contamination.
Check the lift pump is working.
Check the turbo waste gate is not sticking.
Get it on diagnostics.
Click to expand...

That's the beginning of a How To ...
 
Hi Guys

Thanks for all the advice as always.

I am going to clean the intercooler system and change the fuel filter and air filter as part of the service but I might have discovered the problem

I disconnected the MAP sensor and took it for a run, it runs smoother (no boost as expected) but it runs and revs above 3000 rpm without any issues.

Would you suggest that the MAP sensor is the issue if it is running OK without the boost and put it back on and the problem comes back. It does not give you the same pickup for over taking but it runs smoother....................I am ordering a MAP sensor as it must have something to do with it

On another point what is the ID of the leak off pipes as I put some on that just don't seal properly, if anyone can tell me where to get a few metres of it I can cut it to size
 
dubloman said:
Hi Guys

Thanks for all the advice as always.

I am going to clean the intercooler system and change the fuel filter and air filter as part of the service but I might have discovered the problem

I disconnected the MAP sensor and took it for a run, it runs smoother (no boost as expected) but it runs and revs above 3000 rpm without any issues.

Would you suggest that the MAP sensor is the issue if it is running OK without the boost and put it back on and the problem comes back. It does not give you the same pickup for over taking but it runs smoother....................I am ordering a MAP sensor as it must have something to do with it

On another point what is the ID of the leak off pipes as I put some on that just don't seal properly, if anyone can tell me where to get a few metres of it I can cut it to size
Click to expand...
If you electrically disconnected the MAP sensor, it should have flagged a fault. Disconnecting the MAP sensor will not stop boost, the turbo is mechanically regulated, but it should put the engine into a safe mode limiting power output. Are you sure that the spigot in the manifold where the pip to the MAP sensor goes is not blocked?
Are you sure the MAP
 
I have not checked to see if the pipe is blocked, I will do that next

I have just tested the 3 wires on the map sensor power 5 volt ground and sender wire.

I get 5 volts from the power wire and 1.7 volts on the sender wire, I believe this should be 5 volts and it drops depending on the vaccum being produced and it should drop depending on how much vaccum is being created. it could also suggest that the pipe may be blocked as suggested.

I will test the pipe and report back
 
I will admit I am still learning and as I have FMS and spinal issues memory is very poor and any activity is a big issue for me so things I may have known I forget or need to re-teach myself on most tasks....................so sorry if I mess up when I post I am only human.

I have checked the pipe from the MAP sensor to the inlet manifold, it is not blocked but did have a few small splits in the pipe (this would not have helped)

The pipe was not blocked (but forgot to check the spigot) but has now been replaced with new pipe (I will check it shortly for being blocked) but we are still having the same problem. It pulls like a train until it gets to 3250 rpm and then just bogs, if you keep your foot in it will not do anything but if you let the revs drop then you get power back. If you stay below 3000 rpm it is fine but go over and you are hitting a wall with the power.

Could it be the MAP or something else.

I will be changing the fuel and air tomorrow and I am waiting for the degreaser to clean the intercooler system, will brake cleaner do the job as I used to use it a lot to degrease but never tried it on an intercooler.

Thanks for all your great advice
 
Update

Spigot clear, I don't feel it is the wastegate as it doesn't feel like it is over boosting, it feels like the other way

I am going to try fitting the other two pipes from the left hand side of the intercooler when I strip it down to clean it up as I have done the one on the right from manifold to rad so it might be that by changing that failed pipe it will show the weakness in the others as they are all the same age so I should have done them all together.

If my attempt works then I will report back but it might be over the weekend
 
dubloman said:
I will admit I am still learning and as I have FMS and spinal issues memory is very poor and any activity is a big issue for me so things I may have known I forget or need to re-teach myself on most tasks....................so sorry if I mess up when I post I am only human.

I have checked the pipe from the MAP sensor to the inlet manifold, it is not blocked but did have a few small splits in the pipe (this would not have helped)

The pipe was not blocked (but forgot to check the spigot) but has now been replaced with new pipe (I will check it shortly for being blocked) but we are still having the same problem. It pulls like a train until it gets to 3250 rpm and then just bogs, if you keep your foot in it will not do anything but if you let the revs drop then you get power back. If you stay below 3000 rpm it is fine but go over and you are hitting a wall with the power.

Could it be the MAP or something else.

I will be changing the fuel and air tomorrow and I am waiting for the degreaser to clean the intercooler system, will brake cleaner do the job as I used to use it a lot to degrease but never tried it on an intercooler.

Thanks for all your great advice
Click to expand...
We're all in the same boat mate.don't know about brake ckeaner, any residual will be like Easystart when you first start it up.
 
That's what I was thinking but if it is given enough time to dry/drain it should be OK don't you think the gunwash I have never used so don't know what it does

The problem I have is I was a diesel fitter military trained and worked as an MOT tester etc etc prior to me becomming ill, it is hard to learn everything again and again as I should know this stuff and be helping others with my knowledge but it just ain't there anymore

So if I ask a stupid question, bear with me as it is just a process I need to get through

Thanks
 
spill /map pipe is 3.2mm diameter <2meters length does the lot.

White spirit or turps will do for intercooler flush just keep pouring it through again and again then with clean last. I leave it soak over night plugged with rags will show if you have a leak too. Brake cleaner will work also. MAKE SURE you air it out THOROUGHLY before refitting/starting!

Your not supposed to clean MAP sensors with brake cleaner, but I have on one that would have been binned and it worked. Contact cleaner is best I think?
 
Thanks for the guidance, it's as I thought but needed to get confirmation as some things I do seem logical but then I screw up..........it happens

The spill pipe I have is 3.2 and I have fitted it and it works

The problem I am having is the leak off pipes don't want to seal and seem to be weaping at times, I push fit them on but just wanted to check if there is any fix for when they don't seal?

Thanks
 
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