Late turbo kick in

[lukahu]

Hello,

I have a problem with my Peugeot 406 2.0 HDi.
While car is cold it pulls like it should but as it warming up turbo kicks in laser and later.
At working temperature it kicks in on 2900rpm.
But I feel like turbo works from 1800-2200 rpm and than sudden loss of turbo until 2900rpm.
Vacuums are checked, and hoses of turbo and intercooler, replace MAF sensor l, replaced boost sensor.

At least I feel it's kicks in on time while engine is cold, I could be wrong, but you can feel late turbo best in 4th and 5th gear.
It takes forever to go from 2200 to 2900rpm, and after that works fine.
I think I can hear turbo working all the time, and on idle take longer to build boost we comparer 2 same cars with same engine and mine is building boost longer than the other.
If air escaping system you should hear air coming out, but I do not.

If somebody knows what should I look and test I would be greatfull.

[WillNZ]

If you can get or have a mechanical boost gauge, install it (T-piece in pipe connecting the MAP sensor on top of intercooler) and drive it. It will tell you if you are in fact losing boost. If you are losing boost, try swapping the turbo solenoid with the egr solenoid.
Another thing you could try if it is not losing boost is to disconnect the vaccuum pipe from the EGR solenoid (plug it when you do so)/blank off the EGR system at the flange on the intake manifold. If the EGR is opening at the wrong time or not closing properly it will affect running.
I personally have blanked off all my 406's EGR systems as they just cause chaos by gumming up the intake manifold with thick black gummy sludge and causing the motor to run like ...
Another thing to try is to unplug the MAF and see if this sorts out the problem. Non-OEM MAFs often do not perform properly out of the box...

[GingerMagic]

Hi.

I agree you should swap the solenoid over, you can do this while they are still fitted to the bulkhead by swapping just the vacuum pipes and the connectors.

There's should be two, unless you have a very late model that had 3.

Not sure why it's performs worse when it's warm, maybe the coolant temperature sensor is giving duff readings?

You can unplug the MAF, no I'll effects but it may put the management light on the dash - ignore it, it'll go off after a few trips once you plug the MAF back in

Have you checked your air filter?

[486]

Vacuums are checked, and hoses of turbo and intercooler, replace MAF sensor l, replaced boost sensor.

What is the boost sensor?

[WillNZ]

Vacuums are checked, and hoses of turbo and intercooler, replace MAF sensor l, replaced boost sensor.

What is the boost sensor?

Think he is referring to the MAP sensor..?

[GingerMagic]

The MAF sensor ( Mass Air Flow?) is a chunky sensor on the air intake pipe.

It does also detect the boost in a way.

The boost sensor I should imagine would be the MAP sensor ( Mass Air Pressure?) which is mounted on top of the intercooler

The MAP sensor rarely fails, if anything there will be an air leak under pressure in the actual intercooler, boost leak, which you can see in the form of air bubbles in the oil at the bottom...

The MAF is the one that ideally would be replaced, and definitely a genuine one if you can afford it.

I should imagine, after re-reading the original post that blanking the EGR is priority, then swapping the solenoid valve with a known good one.
To check the EGR valve is working, it's possible to suck on the vacuum pipe as hard as you can, and listening to it popping shut with a ping, once you let the air back in.

[486]

The MAF is the one that ideally would be replaced, and definitely a genuine one if you can afford it.

Is there chance that MAF seems OK (from diag values) but is not OK? I know when MAF is replaced the car goes very good but not sure whether to risk and buy new MAF if this is not necessary. The 3rd way is to buy cheap MAF only to test whether there is difference and eventually get genuine/Valeo MAF later. AFAIK, cheap MAFs work fine at least for short time.

[GingerMagic]

Have you driven the car with the MAF unplugged yet - try this next time you go for a drive.

[486]

Unplugged the MAF - the car drives the same way like with connected MAF, i.e. no change. What does this mean? MAF is for replacement or normal?