Loss or lack of power - 1z TDI

[NiGh7]

Hello guys and galls,
I drive a 93' B4 TDI Sedan, 1Z engine.
It will be two months now after the car lost power, perticulary in the lower band (below 2k rpms), its like im towing smth all the time.
I've tried running vag-com diagnostics, there are no fault codes, also no read-outs from the groups.
I've changed the pressure-relief valve on the valve head cover, washed the intercooler and checked the pressure reg. valve (N75) (its within ohm range), also checked the EGR valve controls and the EGR itself. There are no cracks or leaks in the turbo piping. The thing I noticed was that before it lost power it usually ran boost around 1 and peak at 1.2(3), now it barelly goes to 0.95.
Everything working thus far.
I'm open to suggestions.

[Tractor Dave]

Fuel filter blocked or fuel pump dying?

[NiGh7]

Fuel filter blocked or fuel pump dying?

Well, the fuel filter is brand new, at approx. 5k, changed once the symptoms became noticeable.
About the fuel pump, the car starts ok, no judders or stutters, no shaking, no excessive smoke (on the contrary), not much difference in fuel consumption also.
Any way to test the said pump?

[Tractor Dave]

Well, the fuel filter is brand new, at approx. 5k, changed once the symptoms became noticeable.
About the fuel pump, the car starts ok, no judders or stutters, no shaking, no excessive smoke (on the contrary), not much difference in fuel consumption also.
Any way to test the said pump?

You can do a flow test.
My pump recently failed. Worked fine on low revs but low on power and then started to cut out intermittently. It also started to buzz.

[newsh]

Maybe a bad injector?

Not sure how to check the diesel pump, I think there’s a sticky post on here somewhere though.

You can check the N75 works, connect a 12v battery across it it should click.
Also check for boost leaks.

[newsh]

Also
Try it with the N75 unplugged, see what boost you get. On the S2 it would be 0.4Bar on a stock WG spring but not sure what spring the tdi uses.

[NiGh7]

Also
Try it with the N75 unplugged, see what boost you get. On the S2 it would be 0.4Bar on a stock WG spring but not sure what spring the tdi uses.

Its even worse with N75 unplugged.
No boost leaks detected.

You can do a flow test.
My pump recently failed. Worked fine on low revs but low on power and then started to cut out intermittently. It also started to buzz.

Can you walk me through the flow test? I could not find it.

[Tractor Dave]

There was a post about doing one here. Not sure if it's the same on yours but basically disconnect the feed at the rail and by pass the pump relay and measure how much you get in a set period. You can also test pressure if you have a gauge.

[John.]

Not sure if it's the same on yours ........

Are you referring to your S2 Dave ??? 1Z is a diesel, no electric pump.

[Tractor Dave]

Are you referring to your S2 Dave ??? 1Z is a diesel, no electric pump.

My apologies. I thought there was a pump in the tank on that model as per some of the later diesels

[NiGh7]

So, no flow test, any other way to test the pump? or perhaps the MAF/MAP sensors?
Thing I noticed today, with MAP unplugged, the only difference is that there is no turbo whistle, its the same power /no MORE loss either/.

[Tractor Dave]

So, no flow test, any other way to test the pump? or perhaps the MAF/MAP sensors?
Thing I noticed today, with MAP unplugged, the only difference is that there is no turbo whistle, its the same power /no MORE loss either/.

Maybe its this?
https://www.youtube.com/watch?v=yRMTEAKsScE

[Monkeymagic]

Check all the vac pipes behind engine abd firewall. Even the smallest of vac leaks will cause issues on 1Z.
Is there and air bubbles in clear fuel feed line. Vanes on pump sticking and causing poor flow/pressure is common..
Check the short boost hose between intercooler abd throttle body.. They split underneath.

[John.]

I remember checking the air flow on a previous tdi, you're looking for 5v(I think) and earth on 2 of the wires.....and with engine running an output from the sensor which will be constant at idle and vary as the revs increase/decrease. There will likely be a wire for air temp as well?
Apologies if the above lacks detail, it wasn't yesterday!

[NiGh7]

I remember checking the air flow on a previous tdi, you're looking for 5v(I think) and earth on 2 of the wires.....and with engine running an output from the sensor which will be constant at idle and vary as the revs increase/decrease. There will likely be a wire for air temp as well?
Apologies if the above lacks detail, it wasn't yesterday!

Check all the vac pipes behind engine abd firewall. Even the smallest of vac leaks will cause issues on 1Z.
Is there and air bubbles in clear fuel feed line. Vanes on pump sticking and causing poor flow/pressure is common..
Check the short boost hose between intercooler abd throttle body.. They split underneath.

All the vacuum lines are new, changed them the other day, no difference. The N75 was tested once again and its OK, the EGR valve is OK, the wiring to the MAF itself is OK (exact 5v on wires 3 and 4). Sadly I didnt test the MAF with the engine running, simply because i have nothing to test it with.
Open for ideas once again

Maybe its this?
https://www.youtube.com/watch?v=yRMTEAKsScE

The fuel have no bubbles in it, no restrictions.


P.S I think I can try and make a video , just to show you whats wrong.