Help! Bad running and no fault codes

[Spencer superb]

I have a skoda superb 2.5tdi v6 2004 plate. I've had it now for about 2 months. It struggles on long journeys. After about 1.5 hours driving the performance weakens and starts to rattle (like bad tappets noise) if I continue to drive the car it shudders in idle and even cuts out. Engine light was on. The fault found was throttle body. Had it replaced. Still the fault on long journeys but no light now. Took it to skoda today and they plugged vagcom in. No engine/transmission fault found. And they say its a great car no problem. GREAT HELP!! anyway. I want to love this car but I'm finding it hard with this big fault.

I should mention I've tried a full service (fuel and oil and air filters) also. No change.

Please help!!

[rotodiesel]

Take it to a diesel specialist who understands VP44 pumps. I find that VAG dealers generally have no useful knowledge or interest, especially in diesel related problems.

rotodiesel.

[Spencer superb]

Thanks for your reply. How do I know which garages are diesel specialists?

[Danny 57]

You could try Goggle and then make a couple of phones calls in your area, even from the yellow pages be patience there is bound to be someone locally.

[Spencer superb]

Done. Booked in with SAS autos in Guildford on tuesday. If they dont find anything then no fee. After paying Skoda my 2nd diagnostic fee. rubish. Will update this if/when they find anything. Thanks.

[ericsuperbee]

Another good place to try is VAS Motion, by the railway line at Merrow. They looked after my V6TDI brilliantly for the 5 years I worked in Guildford.

Be aware there is not much easy repair on a VP44 pump and VAGCOM will throw up all sorts of faults. If the pump has to come off you are in to front of car off/ cambelt off etc - and you might as well replace cambelt / idler and water pump.

This happened to me this past January at 116k miles; pump repair was c £600 and another £1000 for labour, belts VAT etc. Definitely not a job for an amateur and front of car off work really needs to be done by V W / Audi trained people (but not at their prices!)

Have since covered another 5k miles and the smile is back!

Took mine to Skoda Aldershot - ONCE!! - obviously not a clue at what they were looking at................

[rotodiesel]

Another recommendation for VAS Motion. Thoroughly competent and knowledgeable - I believe started by two ex-VW people who didn't like seeing customers ripped off and vehicles messed up at the dealers.

Normally I do all of my own work, but VAS fitted me in at very short notice for a CV joint boot change (thanks, VAG - they've only been useless for about 10 years) as I had to go abroad on business the following day.

I could not fault their work - and I'm very fussy.

rotodiesel.

[Spencer superb]

Ok update guys. Just back from SAS auto. He checked fuel pump readings and all fine. He couldn't find anything it could be. Suggested that the ECU was playing up and misreading the EGR. So disconnected the air hose from EGR and plugged the EGR. Said to drive and see if fault occurs.

Now this if anything has made it worse. The car is running badly after 40 minutes of driving as a apposed to the 90 minutes before!!

I am very stuck and frustrated, all though he didn't charge anything I just want this car fixed.

Seriously considering selling, after 2 months of ownership.

[CRC]

How long do you have to leave it switched off (after it's started mis-behaving) before it's OK again?

5 mins, 1 hour, 2 hours ....... overnight?

[Spencer superb]

Usually it's left over night. But I'd say about three hours before its ok to drive on short journeys again

[CRC]

Hmmm ..... I'd say the V6 takes about three hours to cool down pretty much completely. They're a big old lump with a lot of thermal inertia and even in the winter, after going to watch a football match for a couple of hours, there's still some residual heat in there as the heater takes nowhere near as long to get warm as it does in the mornings.

However, the fault can show itself after 90 minutes of driving, and I would say that even in the depths of winter, mine is pretty much fully warm after 20 minutes and defintely warm after half an hour or so.

So the fault can take up to an hour from being fully warm to show itself, and then goes away once the car is fully cold again.

Based on that assumption, you tend to think that it might be a temperature related fault, but would expect the ECU to show fault codes if it was a sensor / connector fault on the car.

I suppose it could be a heat related fault on the main ECU or the FPCU that's sat inside the VP44.

I'm not entirely sure what fault codes can be read from the FPCU, but it could just be that prolonged exposure to heat causes a problem, which resets itself when the temperature returns to normal.

If a warm, rotating diesel engine is supplied with the right amount of fuel at the right time, then it should run ......

Only guessing .....

[Spencer superb]

The guy at SAS suggested maybe looking at the mapping of the ECU and sometimes cars can lose their mapping parameters. However, I want to be sure before remapping at £200.

I know remapping would help with running and performance. But would like to be sure

[CRC]

Why would an engine ECU lose it's parameters when it's warm and remember them when it's cold?

My experience with industrial control systems says that once memory gets corrupted, then it stays corrupted.

Type "VP44" into E-Bay and look at the results ..... the ECUs on these pumps live in a tough working environment ........ as I'm sure Rotodiesel will confirm

[Spencer superb]

Thanks for the input. I'm not really clued up on engines to be honest, especially these ones. However what are you suggesting is the problem?

[CRC]

Obviously, I don't actually know what's wrong with your car, but I'm just going through the thought procedure that I would be going through if I was in the same boat.

I'd be thinking that the fault only happens after extended driving periods, so it's probably heat related?

As the fault appears to be a fuelling problem (diesel engines don't have sparks to worry about, the pistons are still going up and down compressing the air to the correct temperature and the valves are still opening and closing correctly), the assumption would be that fuel is being incorrectly delivered to the engine at that time.

The fuel to the V6 is delivered to the VP44 pump by a lift pump in the tank. The VP44 has within it mechanical pumps, advance solenoid, fuel shut off solenoid, position sensor and ECU to control the delivery of the correct amount of fuel to each of the 6 injectors. If any of these components are failing due to heat, then the VP44 will not do what it's supposed to and the engine running will suffer accordingly.

The ECU within the pump has been known to fail (try searching on VP44 on YouTube) and there are companies out there who will test and replace the ECU, indicating that there is enough business available to allow them to offer that service.

That's the path I would be pursuing, but I would be very wary about who I went to for help. The main dealers will want in excess of £2.5k to sell you a new one (sir), so it may well be worth ringing VAS Motion (as suggested in a previous post ) who sorted out ericsuperbee's problem.

Of course, I may be totally and utterly wrong and it could be something else really simple, but these are the joys of owning ageing cars outside of their warranty periods.

[allclownsareevi]

I know this is probably an overly simplistic answer but given that the issue seems to be when the car is run hot, and disappears when cold again, are you certain temp sensors and MAF sensors are sending back solid signals? Do you happen to know somebody else with the same engine you can swap sensors and test?

I'd be surprised if it were the ECU suffering corrupted code.

[Spencer superb]

Just a stab here but could it be anything to do with bad oil in the system? From previous owner.

I did an oil and filter change as soon as I bought the car. But the day after I checked the oil and it was very black after only a 90 mile journey. I know diesels are bad for this. But that seems quite quick to me.

I will give VAS a call next week and try get it down there

[Cown]

The oil will always turn instant black on both the 1.9 and 2.5 engines.

[Spencer superb]

I thought so. Thanks Cown.

Just been reading/watching video on vaccuum leaks causing the same sort of problems as mine. Anyone in the know how think this could be the cause of this mystery fault?

[allclownsareevi]

I thought so. Thanks Cown.

Just been reading/watching video on vaccuum leaks causing the same sort of problems as mine. Anyone in the know how think this could be the cause of this mystery fault?

Easy enough to check for vaccuum leaks. Run the engine at idle and grab yourself a can of WD40 or Carb Cleaner. Spray a mist of it anywhere you think a vaccuum leak may be and listening for the engine note changing in pitch/revs. No change, probably no vaccuum leak.

Not sure why a vaccuum leak would only present itself after a few hours driving though. Worth a shot before you start throwing money at it.

edit: Oh heck, here

to explain better. Edited 20 June, 2013 by allclownsareevi

[CRC]

Extended exposure to heat can cause electronic items to "stall" and then be good as gold again once they've cooled down.

If you run a PC without the CPU cooling fan, it will work fine when cool, but the PC will stall when it gets hot. I've had ethernet cards on industrial PLCs that exhibit the same problem and I once had a Honda Accord that started perfectly throughout the winter, started fine in in the summer when parked in the shade, but would refuse to start when left parked in the full glare of the summer sun.

Turned out it was a known fault with the FI relay which sat inside the cabin and the problem was related to the dodgy soldering on the base of the relay. Whenever it got really hot, it would just not make the contacts. Five minutes spent re-soldering the base of the relay cured the problem for good (and saved £80 for the cost of another one from Honda.)

Just remaking all the electrical connections in the engine bay with a squirt of WD40 (or better a contact cleaning solution) can sometimes work wonders.

Sometimes it really can be a very simple fault that stops things working.