Flat spot at 3600 rpm after service...

So, just completed a full service on the old beastie (2005 td4), oil change and filter, air filter, pollen filter, turbo filter, and fuel filter. I also uprated the PCV to the BMW cyclonic version. I even pipe bypassed the EGR to see what happens... and it's never driven better for the most part.

The car is sharp, quick, responsive, smooth, starts first time... perfect! But... if I accelerate hard I get a drop in power at 3600-3700 rpm between gear changes and the engine management light comes on then goes off again.

tested the car, runs past 70 smoothly, pulls away smoothly and quicker than ever before on a roundabout. Seems to just lose acceleration massively in that one place. It's really odd - the drop is quick in normal mode and prolonged in sports mode, but it's like the car isn't getting enough juice. I know many people will yell "fuel pump!" straight away, but it was perfectly fine before the service. I used a non-LR fuel filter - only thing I can think of. i verified it was nothing to do with the PCV change etc. Everything works perfectly, just a massive flat spot at that point on hard accelerating.

Any ideas? My guess is fueling but I can't believe the pump just died immediately - one hell of a coincidence.

I am wondering if the new responsiveness has highlighted a fuel pump deficiency, but it literally never happened before at full acceleration. IT can't have been THAT much worse...

Anyone know a good test?

I thought my fuel pump was fine, but it just went one day. Actually, on reflection, it had been going for a while, but one day it just decided enough was enough.

How many miles has your TD4 done?

I used a non-LR fuel filter

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what filter did you use ?
if it were an aftermarket budget one .. perhaps it doesn't have the flow capacity ..

How many miles has your TD4 done?

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+1

is the fuel pump noisy at startup?

in any case .. should fuel pressure supply not be able to keep up with demand ( i.e. acceleration )
the ecu will cut the engine power to prevent damage to the high pressure fuel pump

It was a generic one (bearmach? something like that) and could be the issue.

I am not convinced it was the pump as it literally worked two hours before no problems; when I start up to pump is the same as it has always been and I can hear it pumping fuel clearly but not too noisily. When I swapped the filter I turned it on and it filled the filter quickly and efficiently - started first time 60 seconds later.

Car has done 112k I've made sure I've kept everything up - not sure if pump has ever been replaced but I'm honestly not sure it's the pump. Perhaps I should source a proper filter and test that first... don't really fancy replacing the pump unless I know it is at fault.

It does feel more like an ecu cut rather than a failure to fuel - the engine won't rev higher and it feels constrained, rather than struggling per se. You may have hit the nail on the head chaps. Wonder if the (slightly thinner non landy) filter simply isn't allowing the flow.

It was a generic one (bearmach? something like that) and could be the issue.

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do not bearmach? supply LR ( i don't know for sure )
'mahler' are supposed to be good .. ( but don't know who makes the filters for LR )

Car has done 112k

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r.rons site sais the pumps are good for about 100k miles

when i had my filter replaced ( was 10k overdue ) ..
was forced to do it as the engine hit a brick wall at 3500rpm
i also had the pump replaced as a matter of course .. ( vehicle on 75k miles )
new pump is much quieter .. 'n kept the old pump as an emergency spare

Thebpump may have been replaced before (remember the seller saying something) so would rather rule out filter first. Was a 7 quid jobbie so...

After that I guess pump it is.

Just checked... Rimmerbros do the same aftermarket one I got. Forbtue sake of a tenner for the genuine I may just try that. Will let you know!

Before I realised my pump had gone, I was overtaking a slow car and using steptronic and the car didn't change up so I had to. At the time I didn't realise it, but I hit about 3500 rpm ceiling. It just would not rev any higher.

When I realised there was a problem I replicated it all the time. It then got steadily worse, so that the engine management light came on at around 2000rpm.

No problems on that front since changing the fuel pump. I fitted an oem one. Same make as what i removed.

What about the air or fuel sensor? The ECU will not allow higher revs if it doesn't sense the mixture is right?

Epicuser said:

Before I realised my pump had gone, I was overtaking a slow car and using steptronic and the car didn't change up so I had to. At the time I didn't realise it, but I hit about 3500 rpm ceiling. It just would not rev any higher.

When I realised there was a problem I replicated it all the time. It then got steadily worse, so that the engine management light came on at around 2000rpm.

No problems on that front since changing the fuel pump. I fitted an oem one. Same make as what i removed.

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Epicuser:
That is the exacy same scenario I am having. Just waiting for the pump to arrive in order to change it!
Thanks for the very detailed description.

RicardoG said:

Epicuser:

That is the exacy same scenario I am having. Just waiting for the pump to arrive in order to change it!

Thanks for the very detailed description.

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Glad to be of help.

have you checked the vacuum hoses ?, sounds like the turbo vanes not adjusting correctly possible loss of vacuum to solenoid valve.
did you blank off the egr valve vacuum hose ?

I did blank the EGR hose.
I did change my fuel filter and got a little better response but still get the flat spot at 2500 RPM.

This is what my filter looked like:

difficult to say exactly what the problem would be
but certainly be looking at the fuel pump, mine gave me problems for quite a while, wouldnt rev past 3000, and very sluggish,, when it finally gave up, it failed to start, but a little tap got it going again,
also similar symptom is the turbo vanes not responding correctly either, sticking turbo actuator, vacuum solenoid,blocked filter, map sensor ? fuel rail connections

Thanks chaps. So, an update:

I have been ill and at funerals etc so this was the first opp to change the filter.

The official one went in, all greased up. put her back together (I've got changing this thing down to an art form now) and took her for a spin.

WORSE THAN EVER

My guess is that 1) a kink in a hose twixt tank and pump and 2) a narrower aftermarket filter introduced a restriction leading to a false higher pressure. Putting in the proper girth of pump and unkinking the hose has me hitting no power at 3k now and as low as 2.5 if I catch it right.

I therefore deem you are all masterful and correct and I need a new pump worth checking but I will nab one asap and fit.

As to other filters... EVERYTHING else is serviced new. only issue is putting my foot down. I could arse around getting a LR one online but for the sake of a few extra £ I will pick one up from Hunter's tomorrow I guess.

Third time lucky...

In my case it ended up being the LP pump too. Ive replaced it and now my Freelander pulls like a freight train all the way up to 4000. What a difference.

I installed a pressure gauge in the fuel line going to the HP pump and inmediately noticed that things were not up to par. The fuel pressure with engine off and ignition on was 1 1/2 bar. Service manual states it should be 2.2 bar I even drove it around with the pressure gauge hooked on and noticed fuel pressure would drop to 0.9 bar and inmediately got an EML. It would not rev past 2500 rpm

FUEL PRESSURE WITH BAD PUMP


FUEL PRESSURE AFTER LP PUMP REPLACEMENT

I have had a similar problem with my 55 plate Td4 for a while now, pump changed twice with filter, and MAF once due to a latched fault, still with the problem. I am now starting to think turbo, either solenoid or over pressure sensor (if there is one) allowing the vanes to drop to neutral with loss of pressure.

So, good news.

Replacing the pump has sent the freebie darting like an ungainly fat old swallow again. Much improved and very driveable, jumps away from a roundabout as well as it ever will in sports mode.

However, there is an intriguing loose end.

I am still getting a flat spot as if there is not enough fuel... at over 4500 rpm. The car HAS been tuned by a master tuner to provide better economy and cleaer burn, and the temporary EGR bypass is still in place.

It revs pretty high and leaps, and just struggles to change gear with lack of power at very high revs, then jumps into lower gear again. Half second EMG light, and then back to normal.

Given it's more responsive than ever I am more curious than worried. Any ideas?

I will post up a full service list of steps when I get a chance as well.

I am still getting a flat spot as if there is not enough fuel... at over 4500 rpm

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max bhp is @ 4000 rpm

after that power falls off ..
so by 4500 rpm could feel like there's not much ooomph left to be had

maybe your retune did something to the higher rpm response

max governed rpm is @ 4800 rpm
by what means are you reading the rpm ? the tacho dial might be innacurate at higher rpm
or .. are you using a digital readout .. e.g. scangaugeII

i'd debate what point there is taking the td4 up to 4500 rpm anyway ..
i.e. Over the max bhp output rpm of 4000 rpm ..
( don't know about 'remapped' ecu/engines .. maybe rpm power curves change .. and extend ..
( max 'overun' rpm is 5250 .. must be where piston crown says hello to valves and head ..
( and that figure would prudently reduced for an engine that's got mucho miles on the crank/con rods/valve train ..
~~~~~~~

could be simply the air filter can't flow anymore ( is that new ? )
or something else just ain't up to it .. or the eco reprogramming/tuning has shifted something ..

anyhowz .. for an engine that has max bhp at 4000 rpm ..
would not supprise me it 'feels' like it's falling flat-ish at 4500 rpm .. especially when there's only 300 rpm left in the computer controlled kitty