1.6tdii

[Rubbadub]

Morning all

Hoping for a little help if possible,

I’m expecting g this to be something f stupid and something that’s been overlooked.

Daughter bought a caddy 1.6tdi.
Basically it drove all the way home about 70miles fine other than going into limp mode on hills and under load, driven steady it was ok and got upto 70 mph.

Pulls up at home and it’s smoking, injector seals are leaking and the rocker cover is cracked.
Changed rocker cover and resealed injectors that seams to have sorted that, oh and a few split hoses have now been replaced.

Fault codes showing were
P08700 fuel pressure low (sporadic)
P03000 02 heater control sensor 1bank 1 low
P040100 egr insufficient flow

I’ve since found the egr as been blanked.
Leak off on the injectors showed next to no fuel.
And the fuel pressure problem I watched live data on the diagnostic and the fuel pressure actual vs required are very close then under load it will just sporadically drop right off compared to the required, or it will go the other way at times and be more than the required.
Also sometimes the injector volts drop to 0.0v however this might be 2 or 3 of the injectors at a time and not all (which I’d expect when I’m off the throttle)

Is there any wiring faults I need to look out for?
does this sound like something commonly found on caddy’s?

Also the oil pressure light came on 2days ago once we put a flush in the oil as it was gunky, replaced oil and filter yesterday and the filter was about as bad as I’ve ever seen.
New oil and filter and was better for a while but oil light came back on after about 30mins driving so I’m assuming this is all the dislodged crap in the engine, I’ll empty the oil again and remove the sump and clean everything

Any advice would be gratefully received. I’ve done a few bag engine conversions so I’m normally quite good at finding these kind of faults but I’m starting to scratch my head.
Thinking of stripping g the loom down to have a better look.

Also the h02s shows 3ohm at the heater so I think this should be ok


Tia

[Rubbadub]

Just a bit of additional info.

Removed sump yesterday that was full of crap and gunk, no metal or anything though, so all that has been cleaned out including the pickup strainer.
Oil light hasn’t come back on since.

Has the problem is only under load I decided to try a moving leak off test, hoping that when the fault occurred one of the jars would fill up rather quick
That didn’t happen so I think I can rule out the injectors.

The van drives spot on now other that the massive hesitation at 2500-3000 revs
Dosent do it in 1st gear though.

I’m thinking it’s either got to be the pressure regulator or the in tank pump.

HPFP looks new

If anyone has any thoughts it would be appreciated if not I’ll keep plugging away and update

Ta

[STP]

Boost control maybe? And another possibility is if anyone has fitted one of those dodgy power box things which mess with the FPR or even injectors directly to fool the ECU into injecting more fuel, instead of a proper remap. They can and do fail, and cause issues like this. Check for anything plugged in between the rail pressure sensor and the ECU harness original sensor plug.

A hard cut at 3000 rpm for boost errors however would show up in the codes memory. So probably not that.

Are the MAF readings consistent under load? Often they go bad with no codes, but normally idle badly or cut out on pulling away. However this could still be the issue, low airflow values suddenly under load would cut the fuelling back severely.

[Rubbadub]

Thanks for the reply.

I’ve found the fault today
I was checking pump flow to ensure the in tank pump was producing sufficient fuel when I just thought something wasn’t right, quick google to get a picture and sure as hell, someone has put the fuel pump feed and return onto the wrong spigots on the filter.

Van runs lovely thought I’d take it for a run.

Brand new return pipes are leaking now
So now I need to work out why those are leaking.
And the oil pressure light come on again, but I noticed this before when the returns had leaked so not sure if it’s causing a short for something or not or if the diesel is getting into the engine. Anyway changed the oil, and it drove home lovely other than the leak on the return.

So any advice on why this may happen other than cheap parts I would appreciate.

May bite the bullet and order genuine

Ta

[STP]

Leaky returns can probably be sorted with good parts or a bit of fettling, I'd be more worried about the oil pressure.

It's worth dumping the oil and dropping the sump, get a look at the pick up pipe gauze and check the sump inside for sludging. Put another filter on while you're at it.

If you really do have poor oil pressure then all this work could be for nothing if oil starvation kills it.

The Audi 1.8t engines were very sensitive to oil pressure for example and sludging was a common issue. Flushing treatment can dislodge some horrible crap that ends up blocking oil feeds and in that engine it drops the hydraulic cam chain tensioner in the rear (16v twin cam sync chain) from low oil pressure and the engine detonates when the cams lock up. Been there and got the (very expensive) tee shirt.

It began by flickering the oil pressure light after a flush and oil change, did yet another oil change but thought the filter would be fine as we'd just changed it. It wasn't. It went bang soon after. It bent the head like a banana and most of the valves were smashed into it.

The sump had filled with weird rubbery sludge which solidified when cold, and the filter was full of it too. The pickup was also clogged of course. We think the sludge was caused by previous owner using mineral oil instead of synth but will never really know. They don't mix well. We probably dislodged it with the flush.

[Killomiter]

Had trouble also with leak off pipes and found out that the o rings need to be swapped out and the colour of ring is so important. so either change for new rings that match the original and if anyone removes the pipe/s at the injector remember to change the o ring seal.

Regards Andy

[F20KJB]

I’m not sure if it affects these engines but the 1.8t / 2.0tfsi has oil squirters which are spring closed check valves. They fail and allow some oil pressure to be lost giving you a random oil pressure fault at low rpm as it expect to see a certain value.

Be interesting to put a pressure gauge on the oil system and get a genuine reading of what the pressure is and when it’s low.

Might not be relevant but might be worth a check. They’re about a tenner each for genuine. Not great to fit but not horrendous. I’ve never come across a perfect one on a car with over 100k on it