Hello all, looking for a bit of assistance please.

 

A bit of background for those in the mood for light procrastination -

Over the past year we've covered in excess of 20k in our 1.6 Octy hatch, not missed a beat, lovely car. However I did some calcs and figured out just how much we would have saved if I'd have started us off with a dizzle..... 

 

So now we have -

 

 

A T reg Octavia GLX Tdi with extra cat swinging room in the back.

140k miles FSH 4 previous owners, to the tune of - 3 years, 11 years and 2 within the last year. The seller was a bit of a geezer but the car seemed nice and I'm far too trusting. I took it for a quick spin around the block and was happy enough that all was well.

However on the way home Mrs Reviver radios through that it's slower than an advancing glacier and she's not impressed. I assure her it's just a bit sluggish compared to the sprightly 1.6 and she'll learn to live with it.

But once back home I jump in for another ride, and pulling up a hill in 3rd the engine looses some power and I realise that we have trouble. Limp home mode takes over and I concur that this is tediously slow and apologise for inflicting it upon her. 

 

Anyway. I have exhausted the searches on here as best I can to glean as much information as possible. I'm not a diesel man tbh, so had to familiarise myself with a few concepts, but think I've got most things pinned down.

 

The symptoms then -

 

Engine pulls strongly through 1st and 2nd up to red line. No undue noises, sounds or other complaints as far as I can tell. The turbo does perhaps "whizz" or "screech" a bit, but I wouldn't readily declare it as an unhealthy sound - similar to that which I've had on Turbo cars before.

 

Under load / heavy acceleration the engine power cuts at approx -

3200 / 3rd

2800 / 4th

2600 / 5th

 

VCDS scan gives me just one fault code

 

1 Fault Found:
17958 -  Charge Pressure: Control Deviation
        P1550 - 35-10 -   - - Intermittent

 

Which re-appears once cleared and driven.

 

Now we are of course dealing with a wastegated turbo here, so no VNT issues to talk of. This may make life simpler, but perhaps not as we don't have the usual suspect to point to.

 

I'm all set to strip down the induction, boost and vacuum pipework to clean, inspect and replace as neccesary, but struggle to believe this will be the cure / source of the fault given that the car runs fine and boosts well in lower gears. That and it's a tad cold outside so I'm putting it off!

 

What would people suggest is the best course of action?

 

 

 

Are you sure the turbo isn't a vnt one still?

I got my 2001 TDi 90 in Aug and had similar issues but I unplugged MAF and it was a lot better so changed that out and been mint since. Searching 'Mr Muscle' on here might be worth a go. 

I've had a peer down the back of the oil burner to satisfy myself that the windmill is indeed a flanged affair as expected and not the integrated manifold type of the VNT.

 

Will try unplugging the MAF. Presume the ECU will run on a fixed parameter map subsequently.  Incidentally we did this a few weeks back to get a Boxster home that my brother won on Ebay. £35 later he has a Boxster that's working perfectly, hopefully this too will be a quick fix.

 

I've already spent out a few sheckles on a new replacement N18 pressure transducer, my understanding is that this is the earlier quivalent of the N75 - which is not present on the older models. Corrrect me if that's wrong?
Anyway having now swapped in the new N18 it hasn't made any difference, that said this component does only seem to be related to the EGR control?

Should I expect the EGR operating arm to visible move when revving the engine with no load? The flap moves freely enough by hand but doesn't do anything when observed with the bonnet up running.

So there's no vacuum hose going to the turbo then?  That's probably a sure sign its not VNT (you can still have separate turbo/manifold setups whilst keeping VNT).  Might need to hook up VCDS to see what car thinks is wrong.  Probably best sure fire way to go in the right direction from the start.

Ooh ok, I'll take another look, but fairly sure I didn't see any sign of a VNT system down there. Just assumed that if it was a flanged turbo it wouldn't have the VNT system. 99% certain the car shouldn't a VNT being a pre-facelift, '99 with an AGR engine code. 

 

Admittedly the cable is a cheap item and I'm using the free VCDS Lite software, but only fault shown up is the one mentioned above. Not managed to view any live logs of pressure etc. Which I'm not sure I can do with the setup I have. 

If there is a vacuum fed actuator on the turbo then it probably is.

 

Good news if turbo is just flanged on to the manifold, removing it to clean up the sooty VNT mechanism should be a bit easier.

Off the wall maybe, but you say FSH last 4 owners. - When was the last cambelt? I'm asking because if the belt stretches then the fuel timing can change, and that affects power.

Can't recall exact date / mileage, but within last 2 years / 10k. Was done by an independant outfit, but if they had buggered it up I suspect there would be more obvious issues. 

Had a quick hoon up the road and back with MAF disconnected. Stunted the performance somewhat, but still the physical power wall remains at 3200-3500rpm in 3rd where limp mode kicks in.

 

Vacuum line wise, I can see 2 tacked onto the inlet pipe of the turbo, one follows down to the waste gate actuator for sure, the other one dips out of sight.

 

Does anyone feel that this could be an issue related to the EGR valve? If so I'll whip it off over the weekend and give it a deep clean. 

Sounds like a vacuum actuated turbo then do the Mr muscle trick which should assist in cleaning up the vnt. The point when lol mode kicks in for you makes me more confident about this

 

May be of interest to some that I did eventually get to the bottom of this after putting the job off for far too long.

 

Assuming it was a turbo problem I hatched a plan to remove inlet manifold and turbo with intention to thoroughly clean and inspect all related components. 

 

Went under the car with work light to clean up and spray various nuts with penetrating fluid in preperation. It was at this point I spotted a crack in the underside of the hard plastic pipe feeding from the vacuum pump to the bulkhead / brake servo. Pipe replaced and all now functioning correctly! Bitter and sweet. Nice to have a simple fix, but would have been better to have found it months ago. Thoroughly checked all the smaller 4mm "signal" pipe running to and from turbo etc. just managed to miss the obvious slightly further up the line *sigh*

 

Anyone for a set of Tdi exhaust gaskets?

 

The estate  has since been sold now as Mrs Reliant-reviver now has something else and I've inherited her hatch..... and it's problems......