Pulls like a train when cold, but...

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sparg

Active Member
Posts
103
2002 TD5 110. 93K, VGC
First thing in the morning - it's tugging at the leash.

Couple of miles up the road, it's less enthusiastic.

Not stuttering, just - not pulling that well.
Uphill, 55mph, start to lose speed slightly - drop to 4th - and it's still lost a bit more, it might maintain, say, 46-48, but struggling to accelerate at all.

Sometimes, the 'reluctance' starts to manifest just after I've done an overtake - you know, the 40-55 range where many people just stick at 40 on a de-restricted country road. I nip past, but notice that, going from 4th to 5th, it's a bit flat, doesn't really pick up.
In fact, I'd say that the engine sounds slightly laboured

Oh - I tried something today - turned engine off at traffic lights (about 4 mins). When started, it seemed to pull ok for a little way, then 'reluctance' returned after about half a mile.
Thoughts:
fuel (filter, mesh on pump in tank, other?) - pump not noisy.
air: hose delaminating? (which - intercooler to turbo?)

Other: - sensors? - EGR (should that affect it under load?)?

ONe last thing - it does have a tiny, tiny diesel leak (not enough to drip on floor) - there's pressure regulator (something like that) at the back of the block, right hand side - common fault I'm told. It was little enough that it's just passed MOT with it.

Finally,my previous 2002 90 did something similar, though not as pronounced and less often; some days it just went well, others less so. The last time I saw hurtling off, driven by a couple of hoodies, it seemed to be going very well...

My question really is about how to go about diagnosis. I don't want to just change parts at random, so I suppose I'm after a methodical approach to eliminating possible causes one by one.

Anyone else had something similar?
cheers
 
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Sounds like a fuel/air starvation problem.

Here's what I would do.

Check For oil in injector harness.
Check Turbo wastegate is free to move across the range
Check MAF sensor has 2 sensors protruding into the air flow. Then Clean it.
Check Air Filter for cleanliness. Clean AAP.
Remove and Check all intercooler hoses. Check internally very carefully.
Check hose from turbo wastegate actuator to Intercooler metal pipe. Check for cuts/leaks.
Check vacuum pipe to Air filter (not on all TD5s)
Clean MAP sensor and EGR Valve
Check Brakes not binding
Satisfy yourself that the Fuel Pump is ok

Then its on to changing/removing other stuff and more in depth work.
Such as:
Check Fuel Pressure
Replace Fuel Filter
Check for blockage in pipes to Fuel Filter
Drive with MAF Disconnected
and lots of other stuff......

HTH

Chan
 
the EGR would be my first call... disconect the vacuum hoses from the EGR/ILT valves and clog them well with something as to not lose vacuum there... if the symptom will dissapear then that's your problem
 
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Fuel starvation IME...

1- Replace fuel filter
2- Check fuel pressure (@ loaded engine not idling) to try determine whether it is the fuel pressure regulator, fuel pump, or a combination of both.
 
I'm not completely convinced by the starvation argument.
If, sometimes, I turn it off for 30 seconds, then restart - it can have returned to pulling well. That would be consistent with fuel or air starvation. But it continues for a decent while, going off the boil later, sometimes just after I've been using the right foot (overtaking, setting off briskly from a junction)

In fact, once it is slightly reluctant, I can partially compensate by using more right foot - that is, it will still get up to 70, but will take longer.
I even wondered if it was a daft thing like a pedal sensor.

It's getting a fairly consistent 27mpg, which for a 110 countryside use, is not too bad, I suppose. I might have been tempted to put bigger tyres on (33" instead of 31.something) to improve the gearing, if it weren't that sometimes I find myself having to change to 4th when I reckon I shouldn't need to.

My gut feeling is that it's not an airflow, could be a fuelflow, but most likely a mangement problem, perhaps stemming from the MAF or similar
 
I'm not completely convinced by the starvation argument.
If, sometimes, I turn it off for 30 seconds, then restart - it can have returned to pulling well. That would be consistent with fuel or air starvation. But it continues for a decent while, going off the boil later, sometimes just after I've been using the right foot (overtaking, setting off briskly from a junction)

You're quite right, if restarting the engine (= CTRL+ALT+DEL the ECU) restores power then its an engine management issue (limp mode). Suspect oil in loom or ECU cutting back on fueling due to MAF or MAP. Need to interrogate ECU for fault codes & more importantly have live fueling parameters looked at.

How long since injector harness was replaced and red plug + engine harness connectors cleaned and drained of oil?
 
Could it be with the engine under load, there is some leakage past the injector copper seals? This would result in air in the fuel line and hence fuel starvation just when you need it most? Once normal service resumed then the air would be purged and everything normal again. Just a thought...
 
Would imagine some form of very noticeable missing/misfiring should be experienced as gas reenters injectors via the fill ports?

Also exhaust gas leaking past the injector washers usually comes with other symptoms such as difficulties to start, fuel pump gargling, etc.

Another potential scenario is dirt build up in the fuel pump intake filter.

But all in all keeps having the looks of fuel pressure playing up.

HTH
 
Speaking from my own experience of this, misfiring was never a problem. I did have fuel pump problems also but even after that was sorted problems persisted. Eventually got to the point that that it would only go about a mile and die. After a few minutes it would restart and go again for a mile again and die.
Changing the injector washers certainly gave the engine a new lease of life. It was much livelier than it had been which suggests to me that these washers had been deteriorating over time. Is it possible that the problems you are having are indicative of the early stages of a copper washer failing?
 
You're quite right, if restarting the engine (= CTRL+ALT+DEL the ECU) restores power then its an engine management issue (limp mode). Suspect oil in loom or ECU cutting back on fueling due to MAF or MAP. Need to interrogate ECU for fault codes & more importantly have live fueling parameters looked at.

How long since injector harness was replaced and red plug + engine harness connectors cleaned and drained of oil?
Yep, just had a quick furtle -some oil on the red plug under the seat. (I've only had this vehicle a month = 2K miles)
Latest on 'rebooting' - today, it did the opposite: after restarting, it was very reluctant indeed, then after 30 secs, picked up and accelerated.

Now, if oil down the loom were the cause, would I be right in saying it actually MUST be in the ECu already? - in other words, I have to open up the ECU to clean it? (Isopropyl alcohol?).

Also, I'm pretty sure, if it's wicking along the loom - so that, even changing the injector harness won't alter the fact that there's still some travelling along the loom) - it's probably travelling down the outside of individual cables, and inside the loom wrapping - does thast seem right?

So, additional to replacing the injector harness, I should, using some 'blotting' arrangement, try to syphon off oil just back of the red plug.

If, however, it were travelling down the inside of individual cores, between the copper and the insulation, then this wouldn't work..?
 
the oil travels along the copper core get yourself some brake and clutch cleaner and just keep spraying the red plug and the conector at injector harness somtimes takes a few weeks to get rid .shouldnt be oil in ecu but you can open it if you like but be carefull .
get yourself new injector harness £40
 
the oil travels along the copper core get yourself some brake and clutch cleaner and just keep spraying the red plug and the conector at injector harness somtimes takes a few weeks to get rid .shouldnt be oil in ecu but you can open it if you like but be carefull .
get yourself new injector harness £40

thanks - so even after new harness, I may have some few problems for a while.

But, if it is actually affecting the ECU - surely, it must be in there, to cause very slight signal shorting?
 
i dought it my red plug was like an oil slick but none in ecu .
when you clean plugs she will run good for a day maybe then you have to clean again and again bit of a pain but new wire harness for engine bay is £250 quid ,so a couple off cans will cost £6.
nothing to loose give it a try injector harness will take half hour or so to fit
 
i dought it my red plug was like an oil slick but none in ecu .
when you clean plugs she will run good for a day maybe then you have to clean again and again bit of a pain but new wire harness for engine bay is £250 quid ,so a couple off cans will cost £6.
nothing to loose give it a try injector harness will take half hour or so to fit


Right - so the signal shorting actually occurs at the red plug itself, then?
 
IME the oil in loom problem cannot be fixed, only kept at bay by regularly replacing the injector harness and cleaning the affected connectors. Oil enters and travels conductors by capillary effect (between copper wires and insulation) aided by vibration.

Re oil entering ECU although not frequent this can happen (check for oil stains around the tiny ports on the back of the ECU, one @ ea corner). AFAIK the circuit board is varnished with some form of insulating coating --reckon oil ingress would have to be massive to cause a short there.

The 'reluctancy' to go even after the reboot would indicate some sensor output playing up? Need to get live readings to say.
 
it is the dirty oil that cuases broplems with connectors in the plug giving an unbalenced signal so to speak

+1 on that

New oil is non-conductive, as it 'wears out' it becomes more and more acidic which increases its conductivity (which BTW is very marginal)
 
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