P38A 1999 2.5 DSE down on power

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ar1g3

ar1g3

Active Member
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Belgium
Hi all, I have an issue (I think) with my 1999 p38 2.5 DSE auto. I am not sure there is an issue because I never drove the car without engine issues, and it's my first car with automatic transmission. So I don't know what is normal..

So some background:
  • I got the car with leaky injection pump and cutting out when lifting off the gas.
  • I have also spotted a hot start box
  • Car is a bit tatty
  • Changed the pump seals including lower one
  • Dismantled the fuel quantity regulator inside the pump to clean everything out. A previous fix someone did with RTV caused some contamination inside. This was the cause if the cutting out when lifting off throttle I think.
  • When I put everything back together the car felt sluggish and the auto box was not working nicely engine revving very high. Turned out to be the vacuum line to the MAP sensor next to fuel filter, I forgot to connect it.
  • MAP sensor connected the car changes gear normally but still revving high to my liking
Now I think the car is still down on power. The engine revs easily but it's sluggish. Not much bite when setting off, power only arrives once you git 2700 rpm or so. I have a suspicion that there is a boost problem. How could my works (removing intake etc) have caused this? Or is it maybe something else?

I know taking the fuel quantity sensor apart is tricky and I don't have the equipment to recalibrate it. However as I understand it as long as it is within an acceptable range it calibrates itself at each ignition on. The fuel quantity sensor is the part under the upper lid of the pump. To set the fuel quantity regulator itself I used the hammer back and forward technique.

Or can it be a vacuum leak in the intake? Normally I would say this wouldn't be an issue with a diesel but since there is a MAP sensor and what seems to be a MAF sensor maybe it is?

Any pointers? I did the obvious thing to check if all hoses are connected etc.
 
No powe
ar1g3 said:
Hi all, I have an issue (I think) with my 1999 p38 2.5 DSE auto. I am not sure there is an issue because I never drove the car without engine issues, and it's my first car with automatic transmission. So I don't know what is normal..

So some background:
  • I got the car with leaky injection pump and cutting out when lifting off the gas.
  • I have also spotted a hot start box
  • Car is a bit tatty
  • Changed the pump seals including lower one
  • Dismantled the fuel quantity regulator inside the pump to clean everything out. A previous fix someone did with RTV caused some contamination inside. This was the cause if the cutting out when lifting off throttle I think.
  • When I put everything back together the car felt sluggish and the auto box was not working nicely engine revving very high. Turned out to be the vacuum line to the MAP sensor next to fuel filter, I forgot to connect it.
  • MAP sensor connected the car changes gear normally but still revving high to my liking
Now I think the car is still down on power. The engine revs easily but it's sluggish. Not much bite when setting off, power only arrives once you git 2700 rpm or so. I have a suspicion that there is a boost problem. How could my works (removing intake etc) have caused this? Or is it maybe something else?

I know taking the fuel quantity sensor apart is tricky and I don't have the equipment to recalibrate it. However as I understand it as long as it is within an acceptable range it calibrates itself at each ignition on. The fuel quantity sensor is the part under the upper lid of the pump. To set the fuel quantity regulator itself I used the hammer back and forward technique.

Or can it be a vacuum leak in the intake? Normally I would say this wouldn't be an issue with a diesel but since there is a MAP sensor and what seems to be a MAF sensor maybe it is?

Any pointers? I did the obvious thing to check if all hoses are connected etc.
Click to expand...
No power low down is normal, all the action occurs after half throttle. Unplug the MAF sensor and see if it makes a difference.
 
Datatek said:
No powe

No power low down is normal, all the action occurs after half throttle. Unplug the MAF sensor and see if it makes a difference.
Click to expand...
For me all the action is at full throttle. I need about half throttle to keep speed. Did a 200km drive this weekend over a mix of mild hilly motorways and flat A and B roads managing 15l/100km which is on the high side I think. Feels like I lack boost.

Thanks I'll unplug the MAF and see what that does.

I'm also going to replace the vacuum line to the MAP sensor in case it is split and I don't get any boost fueling.

For what is the MAF used in the engine management? EGR management?
 
Like Data says these arent very torquey low down, i think around 2k is when they start to get going. I have experienced a damaged MAF wire in a 3 series with the same engine and it did make it worse. I seem to remember it was about 2.5k then before any power
 
ar1g3 said:
Hi all, I have an issue (I think) with my 1999 p38 2.5 DSE auto. I am not sure there is an issue because I never drove the car without engine issues, and it's my first car with automatic transmission. So I don't know what is normal..

So some background:
  • I got the car with leaky injection pump and cutting out when lifting off the gas.
  • I have also spotted a hot start box
  • Car is a bit tatty
  • Changed the pump seals including lower one
  • Dismantled the fuel quantity regulator inside the pump to clean everything out. A previous fix someone did with RTV caused some contamination inside. This was the cause if the cutting out when lifting off throttle I think.
  • When I put everything back together the car felt sluggish and the auto box was not working nicely engine revving very high. Turned out to be the vacuum line to the MAP sensor next to fuel filter, I forgot to connect it.
  • MAP sensor connected the car changes gear normally but still revving high to my liking
Now I think the car is still down on power. The engine revs easily but it's sluggish. Not much bite when setting off, power only arrives once you git 2700 rpm or so. I have a suspicion that there is a boost problem. How could my works (removing intake etc) have caused this? Or is it maybe something else?

I know taking the fuel quantity sensor apart is tricky and I don't have the equipment to recalibrate it. However as I understand it as long as it is within an acceptable range it calibrates itself at each ignition on. The fuel quantity sensor is the part under the upper lid of the pump. To set the fuel quantity regulator itself I used the hammer back and forward technique.

Or can it be a vacuum leak in the intake? Normally I would say this wouldn't be an issue with a diesel but since there is a MAP sensor and what seems to be a MAF sensor maybe it is?

Any pointers? I did the obvious thing to check if all hoses are connected etc.
Click to expand...

If it was cutting out when lifting off then the FIP needs a complete refurb, your lift pump might also be weak or stopped working (Wammers did a post in the Technical Section on how to check the output) and the timing chains are probably stretched. You might get away without doing the chains with decent pump(s) and setting the static timing as per RAVE. Note the section in RAVE on replacing the cam-shaft and check the part about using a shim under the cam-holding tool to get the cam in the right position before tightening up the new cam-bolt. I am sure that also helps with starting and running. I'd leave the hotfix. Unless it is broken it won't cause issues.
 
Turbo kicks in around 1750 rpm although the auto is way more sluggish than the manual. Check all turbo hoses for delamination inside and that the hoses are done up tight on reassembly. Also worth cleani g out the intercooler - I just use petrol and then leave it in the sunshine for an hour to dry afterwards. I suspect yours is more a fuelling issue though.
 
ar1g3 said:
For me all the action is at full throttle. I need about half throttle to keep speed. Did a 200km drive this weekend over a mix of mild hilly motorways and flat A and B roads managing 15l/100km which is on the high side I think. Feels like I lack boost.

Thanks I'll unplug the MAF and see what that does.

I'm also going to replace the vacuum line to the MAP sensor in case it is split and I don't get any boost fueling.

For what is the MAF used in the engine management? EGR management?
Click to expand...
Check the manifold spigot for the MAP pipe is not blocked. The MAF fine tunes the fueling to meet emissions regs of the time and controls the EGR, on both mine it appears to effectively replace the MAP sensor as they both run fine with the pipe MAP pipe off. I think on later engines the MAP is no more than an over boost sensor.
With the MAF unplugged, the engine runs on default values and you may see smoke on hard acceleration. A duff MAF is known to restrict performance.
 
Last edited:
Datatek said:
Check the manifold spigot for the MAP pipe is not blocked. The MAF fine tunes the fueling to meet emissions regs of the time and controls the EGR, on both mine it appears to effectively replace the MAP sensor as they both run fine with the pipe MAP pipe off. I think on later engines the MAP is n more than an over boost sensor.
With the MAF unplugged, the engine runs on default values and you may see smoke on hard acceleration. A duff MAF is known to restrict performance.
Click to expand...

That's a good point. Early engine seems to need the MAP pipe.
 
MAF on EGR models was explained to me like thus
Wammers explains how MAF works on my P38


Right then, on EGR equipped cars IAT is a low preset in the ECU. ECU relies on MAF for running air temp readings. Normally if you have EGR fitted but disconnect the vac pipe to EGR valve car will run normally without issue. However EGR only runs at a steady fairly lightly loaded road speeds. It does not work at idle or on acceleration or when the engine is under load. If the MAF has gone duff and is feeding crap to the ECU the ECU may think EGR is operating and prevent high load fuelling. The ECU will only allow fuel to be injected that can be cleanly burned by what it thinks is the oxygenated air present in the cylinder. If the MAF is telling the ECU the airflow has dropped as it does when EGR is active, then that will cause your problems. If you run the car with MAF disconnected in your case the preset will be used for IAT. This may slightly change fuel usage as the fine metering adjustment extrapolated from IAT/ fuel temp and engine temp will not be as fine. Fitting good MAF is best option.
 
Rubberknees said:
MAF on EGR models was explained to me like thus
Wammers explains how MAF works on my P38


Right then, on EGR equipped cars IAT is a low preset in the ECU. ECU relies on MAF for running air temp readings. Normally if you have EGR fitted but disconnect the vac pipe to EGR valve car will run normally without issue. However EGR only runs at a steady fairly lightly loaded road speeds. It does not work at idle or on acceleration or when the engine is under load. If the MAF has gone duff and is feeding crap to the ECU the ECU may think EGR is operating and prevent high load fuelling. The ECU will only allow fuel to be injected that can be cleanly burned by what it thinks is the oxygenated air present in the cylinder. If the MAF is telling the ECU the airflow has dropped as it does when EGR is active, then that will cause your problems. If you run the car with MAF disconnected in your case the preset will be used for IAT. This may slightly change fuel usage as the fine metering adjustment extrapolated from IAT/ fuel temp and engine temp will not be as fine. Fitting good MAF is best option.
Click to expand...
The MAF contains an IAT. In the ECU, there is an unused default value for the IAT sensor fitted in the manifold pre MAF which is not present with the plastic manifold.
 
Rubberknees said:
MAF on EGR models was explained to me like thus
Wammers explains how MAF works on my P38


Right then, on EGR equipped cars IAT is a low preset in the ECU. ECU relies on MAF for running air temp readings. Normally if you have EGR fitted but disconnect the vac pipe to EGR valve car will run normally without issue. However EGR only runs at a steady fairly lightly loaded road speeds. It does not work at idle or on acceleration or when the engine is under load. If the MAF has gone duff and is feeding crap to the ECU the ECU may think EGR is operating and prevent high load fuelling. The ECU will only allow fuel to be injected that can be cleanly burned by what it thinks is the oxygenated air present in the cylinder. If the MAF is telling the ECU the airflow has dropped as it does when EGR is active, then that will cause your problems. If you run the car with MAF disconnected in your case the preset will be used for IAT. This may slightly change fuel usage as the fine metering adjustment extrapolated from IAT/ fuel temp and engine temp will not be as fine. Fitting good MAF is best option.
Click to expand...

Makes sense. Pre-MAF it used the air-temp with the pressure to work out the volume of air for combustion. MAF gives the value direct to ECU I suspect.
 
I'd go back to the pump and check the pump placement, also if you have a nanocom or something that can read the modulation. This engine will run without a manifold installed and no faults. If both the maf and map are unplugged it'll run on defaults as said if the issue remains then go back to the last job down and recheck everything. ;)
 
Mark Piercy said:
I'd go back to the pump and check the pump placement, also if you have a nanocom or something that can read the modulation. This engine will run without a manifold installed and no faults. If both the maf and map are unplugged it'll run on defaults as said if the issue remains then go back to the last job down and recheck everything. ;)
Click to expand...

Certainly if the top of that FIP has been moved that can cause issues. Fractions of a millimetre required to get it idling at 750 rpm. If the top has been off then sometimes a 30 or 40 mile run seems to settle it down.
 
Thanks all!

I cleaned the MAF sensor with contact cleaner, replaced the hose clamps in the inlet before the turbo (they were bit broken) and I replaced the vacuum line to the MAP and checked if the MAP connection on the manifold was clear. No noticeable improvement unfortunately.

It's not like there is a major issue, it still pulls but it changes gear quite late and seems to only have some push above 2750 rpm.

I did mess about with the pump using the hammer technique before but this was the best I could get. I will try again. I have Nanocom but not for this engine, only for my V8.

To demonstrate how deep I went in the FIP:
AJFCJaUnTvFaif__9rNVDEUIQddnUfrkkcmSn3y6mLC5i0opAa4lg-O7MY8FCCDYQTnMJoi0Lhs7sGJyqNcfn2DsMRpvtB-I9zx_im0x4ZBnq7k7HMV1GQvy6TTWMDTED7OG5lNacrwX7pxUdmF_q0Q2nOVv=w1082-h811-s-no

The main two things I have doubts about:
- FIP positioning (will try to further finetune but previously without succes)
- fuel quantity sensor calibration

Anybody went this deep yet? Anybody any idea about how the fuel quantity sensor works? I know on VW's the fuel quantity sensor does a sweep at ignition on to calibrate itself, but you have to make sure that it's mounted so that the lower and upper values are within the calibration range.
 
ar1g3 said:
Thanks all!

I cleaned the MAF sensor with contact cleaner, replaced the hose clamps in the inlet before the turbo (they were bit broken) and I replaced the vacuum line to the MAP and checked if the MAP connection on the manifold was clear. No noticeable improvement unfortunately.

It's not like there is a major issue, it still pulls but it changes gear quite late and seems to only have some push above 2750 rpm.

I did mess about with the pump using the hammer technique before but this was the best I could get. I will try again. I have Nanocom but not for this engine, only for my V8.

To demonstrate how deep I went in the FIP:
AJFCJaUnTvFaif__9rNVDEUIQddnUfrkkcmSn3y6mLC5i0opAa4lg-O7MY8FCCDYQTnMJoi0Lhs7sGJyqNcfn2DsMRpvtB-I9zx_im0x4ZBnq7k7HMV1GQvy6TTWMDTED7OG5lNacrwX7pxUdmF_q0Q2nOVv=w1082-h811-s-no

The main two things I have doubts about:
- FIP positioning (will try to further finetune but previously without succes)
- fuel quantity sensor calibration

Anybody went this deep yet? Anybody any idea about how the fuel quantity sensor works? I know on VW's the fuel quantity sensor does a sweep at ignition on to calibrate itself, but you have to make sure that it's mounted so that the lower and upper values are within the calibration range.
Click to expand...
There is not much poke below 2750. Get the engine module for your Nanocom and check the modulation. You will also be able to check the MAP sensor and turbo are working.
 
Datatek said:
There is not much poke below 2750. Get the engine module for your Nanocom and check the modulation. You will also be able to check the MAP sensor and turbo are working.
Click to expand...
The thing is that the car is up for sale and I'm not willing to buy the Nanocom module for a single use. I am already making a loss on the car. That's why I used the hammer method.
 
ar1g3 said:
Thanks all!

I cleaned the MAF sensor with contact cleaner, replaced the hose clamps in the inlet before the turbo (they were bit broken) and I replaced the vacuum line to the MAP and checked if the MAP connection on the manifold was clear. No noticeable improvement unfortunately.

It's not like there is a major issue, it still pulls but it changes gear quite late and seems to only have some push above 2750 rpm.

I did mess about with the pump using the hammer technique before but this was the best I could get. I will try again. I have Nanocom but not for this engine, only for my V8.

To demonstrate how deep I went in the FIP:
AJFCJaUnTvFaif__9rNVDEUIQddnUfrkkcmSn3y6mLC5i0opAa4lg-O7MY8FCCDYQTnMJoi0Lhs7sGJyqNcfn2DsMRpvtB-I9zx_im0x4ZBnq7k7HMV1GQvy6TTWMDTED7OG5lNacrwX7pxUdmF_q0Q2nOVv=w1082-h811-s-no

The main two things I have doubts about:
- FIP positioning (will try to further finetune but previously without succes)
- fuel quantity sensor calibration

Anybody went this deep yet? Anybody any idea about how the fuel quantity sensor works? I know on VW's the fuel quantity sensor does a sweep at ignition on to calibrate itself, but you have to make sure that it's mounted so that the lower and upper values are within the calibration range.
Click to expand...

Been in there once this deep. I had to knock the top of the pump about to get it steady at 750rpm. After that it was a bot shakey but after 40 miles or so of driving it seemed to sort itself out.
 
ar1g3 said:
The thing is that the car is up for sale and I'm not willing to buy the Nanocom module for a single use. I am already making a loss on the car. That's why I used the hammer method.
Click to expand...
Depending where you are located, there may be someone nearby with a Nanocom. The hot film MAF used for the diesel is not like the hot wire device used on the petrols, I have never heard of one being successfully cleaned. Have you tried running with the MAF unplugged?
 
Datatek said:
Depending where you are located, there may be someone nearby with a Nanocom. The hot film MAF used for the diesel is not like the hot wire device used on the petrols, I have never heard of one being successfully cleaned. Have you tried running with the MAF unplugged?
Click to expand...
Interestingly it did work cleaning mine on my Freelander diesel and that much like the range rovers only like the Bosch MAF that cost on arm and a leg but maybe mine wasn't too bad as It only felt a little sluggish nothing major and no codes coming up so probably wasn't too bad.

I can see why in theory cleaning would work as you think how quickly you windscreen gets dirty with all the fumes from other cars even going through an air filter the MAF is going to get some of that too and being small it would only require a bit to coat it. Personally the way I see it if its suspected MAF anyway it doesn't hurt to try and clean it because if it doesn't work your gonna need a new one anyway.
 
Khemitude said:
Interestingly it did work cleaning mine on my Freelander diesel and that much like the range rovers only like the Bosch MAF that cost on arm and a leg but maybe mine wasn't too bad as It only felt a little sluggish nothing major and no codes coming up so probably wasn't too bad.

I can see why in theory cleaning would work as you think how quickly you windscreen gets dirty with all the fumes from other cars even going through an air filter the MAF is going to get some of that too and being small it would only require a bit to coat it. Personally the way I see it if its suspected MAF anyway it doesn't hurt to try and clean it because if it doesn't work your gonna need a new one anyway.
Click to expand...
As you say no harm in trying to clean the MAF. It works on the hot wire types but seemingly not on the hot film types.
 
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