TD5 low power Air flow fault

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Danastle1992

Member
Posts
32
Location
Derbyshire
Hi guys!

First post so bare with me :)

Right, I've recently purchased a 1999 discovery 2 TD5, amongst all it's other problems I have found that it is absolutely gutless! Now I owned a discovery 4 before this which was very powerful so I thought I was comparing this to that, but since having a second opinion it seems I was not imagining it.
I had a trailer on the back which with contents weighed around 2.3 tonnes and even on flat ground I was having to slip the clutch 2-3 times to even get moving.
I plugged the diagnostic machine in and got this
- Air flow sensor circuit
-intermittent high signal

Now after doing some googling there doesn't seem to be a definitive answer to wether it's the MAF or not.
I did live data readings and got
-52-54 at idle
-270-300 at 3000 revs
Then when I let go of the throttle it dropped to 32-33 and then after 20 seconds or so it crept it's way back up to 52 ish.

I've already checked the Wastegate and that is not sticking, I've bypassed the boost controller because that was Brown bread and I've cleaned the MAP sensor which was absolutely caked in crap!

Any suggestions?

Thanks
Dan.
 
Danastle1992 said:
I'm going to order a delete kit tomorrow, I might also order an inlet manifold gasket so I can take that off and give it a good clean then report back, thanks!
Click to expand...
Well worth doing, I did all that with a new MAF as well the difference was surprising...
....you'll still want a stage 1 map after a few weeks
 
I don't think I'll be replacing the MAF just yet as I unplugged it and went for a run and it appeared to make little difference, but looking at the code even though it's MAF related, there could be other reasons as things like the egr valve seem to have an effect on it for some reason, I've got a horrible feeling it's going to be a nightmare to trace! I don't want to waste £150 ish on a genuine air flow sensor and it make no difference.

My plan in the long run after I've done the clutch and attempted to sort the gearbox and transfer box leaks out are to eventually get it remapped, then maybe later on go for an updated intercooler and stage 2 but that's a long way off yet!
 
Egr blanking kit came this morning so I've fitted it and believe it or not, the egr valve was working as it should and it was closed when I removed it with a good seal so there were no exhaust gases going in permanently, I might have to bite the bullet and try a new MAF but as I said, unplugging it made little to no difference.

Any ideas?
 
Danastle1992 said:
I don't think I'll be replacing the MAF just yet as I unplugged it and went for a run and it appeared to make little difference, but looking at the code even though it's MAF related, there could be other reasons as things like the egr valve seem to have an effect on it for some reason, I've got a horrible feeling it's going to be a nightmare to trace! I don't want to waste £150 ish on a genuine air flow sensor and it make no difference.

My plan in the long run after I've done the clutch and attempted to sort the gearbox and transfer box leaks out are to eventually get it remapped, then maybe later on go for an updated intercooler and stage 2 but that's a long way off yet!
Click to expand...

Gen MAFs are generally around £80, however can be bought for as low is £50 if you look hard enough on ebay. Can be genuine, VDO or Siemens.

Cleaning the inlet manifold is well worth it, some can be so badly caked the reduce the inlet by up to 50%!! Generally very easy to remove.

Other things to help things along is the airbox mod. Open up your airbox and pull out the "impeller". With it removed the engine can draw in air far more easily. Cant put a pic up due to them all being Photobucket hosted, so google TD5 Airbox Mod.

Id double check the air intake pipe work isnt blocked at all and the air filter is in good nick.
 
If you have nanocom record a live data log from inputs fuelling, if unplugging the MAF made no difference dont spend on a new one it can be AAP or MAP/IAT issue cos Eu2 modells are using those for fuelling calculations, the MAF is more important for Eu3 engines, also if the depression controll valve is old better replace that than the MAF ... you have to troubleshoot and restore the power with unpluggged MAF then if you feel it well get a new one and that will improve it more, remove the air filter and go for a drive test without it and see then cos it's possible that the MAF is good and the air flow is low in reality
 
Some great info there, I will be going through these over the next few days!
I haven't got nanocom but I've got access to a dealer level system that gives me live readings etc so I will record the fuelling inputs and other stuff and report back!

Thanks :)
 
Right I've gone through some stuff today, I've cleaned the MAF and it looks intact
Cleaned the MAP sensor which was clean anyway
Checked the red ecu plug and there was no oil
Checked Wastegate again and that's fine
No boost leaks
The DPV was clean but I can blow through both sides, not sure if that's correct?

I've also done some live data at idle

Inlet manifold pressure 101-102 kpa
Inlet air temp 28 degrees c engine warm
Ambient pressure 101.79 kpa
Air mass flow 51 kg/h idle
Air mass flow 300-320kg/h at 3k revs
Says in low when in high and vice versa
Cylinder 1 balance 0 -3 rpm
Cylinder 2 balance 0- 4 rpm
Cylinder 3 balance -2 3 rpm
Cylinder 4 balance 0 - 5 rpm
Cylinder 5 balance -2 3 rpm

Can anyone see anything wrong here?
I've found an old thread on mass air flow sensors that says at 3000 revs it should be showing 600-650kg/h of air where mine is only showing 300-320kg/h
Not sure if this is correct or not
 
No as for some reason the laptop won't record anything so I didn't think it was safe to do on my own, I tested the MAF whilst driving under load this morning and the results are the same as just revving it on the drive, forgot to add - the MAF has two filaments in it which from some Google searching suggests it's an aftermarket one but it says Siemens on it. Also the air flow intermittent high signal fault has not returned although I've only done a few miles since clearing
 
Air flow on the low side, should be minimum 48 at idle... Decompression control valve perhaps? Air filter ok?
 
Discodevon said:
Air flow on the low side, should be minimum 48 at idle... Decompression control valve perhaps? Air filter ok?
Click to expand...

It is at 51-52 ish at idle, decompression valve I can blow through it both ways, not sure if it's buggered but I'm going to order one anyway, air filter is brand new done less than 100 miles
 
Ideal MAF at idle is around 55, that 320 is irrelevant as long as we dont know the MAP reading at that point, ideal maximum MAF reading UNDER LOAD is around 600+ provided the MAP is around 230 then cos the boost and the sucction must be related ...also a good MAF must have 2 filaments... you can't check the DCV just by blowing throug it the only way to rule it out 100% is to put a new genuine one
 
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