Lack of magic (boost) - UrS4

[hunker7]

Hi guys. Not seeing more than 1.7 bar of boost? No error codes and no boost leaks. Checked all important vacuum lines and all is in order. Throttle burried, will go to 1.7 and sit there. Car doesn't misfire.

what are symptoms of fuel pump being on its last legs?

there seems to be leak new exhaust manifold, could that cause issues?

[newsh]

1.7 absolute pressure on the UrS dash is 0.7 Bar of “boost”
Disconnect N75 and see if it’s still only 0.7 Bar. This will tell us if the N75 is doing anything at all.
The stock spring should only give about 0.4 Bar (can’t remember if you have a stronger spring in the WG).

[hunker7]

N75 was replaced by MAC3 solenoid on this car was seeing 1.5/1.6 at a push, and I suspected that might be the culprit, I've fitted my brand new OEM N75 and now ticks over to 1.7.

I would try ECU out of mine but it's an auto where mine is manual.

[newsh]

So does boost drop to 0.4 with N75 unplugged?

Check vac line to ECU and moisture trap is not cracked.
Check knock sensors are torqued correctly.

[hunker7]

Drops to 1.3.

vacuum lines are all good, one of the first things I checked and knock sensors torqued to 10nm.

Comes with Nothelle ECU so isn't standard.

[Error404]

Knock sensors should be torqued to 20nm.
if they are original, I would replace them as a matter of course. Normally they are so degraded you can crumble them in your fingers.

[hunker7]

Knock sensors should be torqued to 20nm.
if they are original, I would replace them as a matter of course. Normally they are so degraded you can crumble them in your fingers.

I believe they've been replaced. Wires were in good condition and intact. I will re-torque them, just to be 100% sure.

[newsh]

Does the ECU in an auto car interact with the transmission in some way?
Just a thought.
You’ve checked the DV diaphragm? Doesn’t show up in a boost leak test unless you pull the vac line to it.
Same with the one-way pcv valve, a leaky one doesn’t show unless you disconnect the PCV hose from the maf hose.

[hunker7]

Does the ECU in an auto car interact with the transmission in some way?
Just a thought.
You’ve checked the DV diaphragm? Doesn’t show up in a boost leak test unless you pull the vac line to it.
Same with the one-way pcv valve, a leaky one doesn’t show unless you disconnect the PCV hose from the maf hose.

You think problem with auto box and that's why it's holding back?

Checked DV by applying vacuum to the small vacuum hose : all good.

PCV valves both replaced and hold vacuum/pressure.

[newsh]

Possibly..

[K Simmonds]

Knock sensors should be torqued to 20nm.

If they are original, I would replace them as a matter of course. Normally they are so degraded you can crumble them in your fingers.

The torque for the knock sensors is absolutely critical, I'd undo them completely and clean the both the contact surface on the block and sensor with a fine wire brush before reinstalling them.

Should you require them I have a set of nearly brand new ones.

Otherwise I think John has got you covered with good advice.

[hunker7]

No luck. Torque to 20nm and still won't see more than 1.6bar. Weird thing is it doesn't misfire just sits at 1.6 bar, so ignition system is good and fuel is getting supplied too.

just seems extremely sluggish.

[fish]

Blocked cat? Knackered WG spring?

[psiconauta911]

I had something similar to what you described and had to much play on the WG valve letting the exaust gases escape and not building boost! it started by not reaching maximum boost till I could only get 4psi and had to have the WG reconditioned and all the boost was back again.
Dismantel the top of the WG and check the valve shaft for play lateraly!