T4 Boost cut off!

[Alex121]

Originally Posted by tt82

Sounds very much like the problem my brother had with his Audi 1.9Tdi. That would go into limp mode for no reason. A VAG specialist reckoned a new turbo as the old one was over boosting. Me, my dad and my brother all reasoned that if the turbo was overboosting, then it was certainly fine. If I remember correctly we narrowed it down to 3 things.

1 Intake pressure sensor
2 Wastegate sticking
3 A control valve that was operated by vacuum pressure

Hmm, well it can't be the turbo or wastegate as they are both only a few months old, can't be the control value either as that was replaced.

Do these cars have intake sensors?

[malteser]

Why don't you turn the actuator down one turn and see how you go?
I had the same problem on mine once and that cured the problem.

[Alex121]

Originally Posted by malteser

Why don't you turn the actuator down one turn and see how you go?
I had the same problem on mine once and that cured the problem.

Hi Danny, how you doing buddy?

Ashok suggested that too, unfortunately a few months back when the issue started I tried that. Took it right back to 15 psi and within a week it was doing it again...

[pierremcalpine]

Why don't you find yourself another Known good MAF and throw I on temporarily to see if anything changes. May want to dump that air filter first though...

[SIAMBLUE]

I would fit a manual boost controller and then you will know the BCS isn't spiking.or fit a EBC if you can afford it.

[gazO2V40T4]

Originally Posted by Alex121

Hmm, well it can't be the turbo or wastegate as they are both only a few months old, can't be the control value either as that was replaced.

Do these cars have intake sensors?

They have a sensor on the intercooler which I believe is an atmospheric pressure sensor they also have the map sensor in the intake pipe

[tt82]

Originally Posted by Alex121

Hmm, well it can't be the turbo or wastegate as they are both only a few months old, can't be the control value either as that was replaced.

Do these cars have intake sensors?

I would imagine there would be a pressure and temperature sensor after the intercooler. Turbo Diesels do and I don't see why Petrol should be different!

[malteser]

Originally Posted by Alex121

Hi Danny, how you doing buddy?

Ashok suggested that too, unfortunately a few months back when the issue started I tried that. Took it right back to 15 psi and within a week it was doing it again...

All good here Alex sorry for late post been moving flat lol

Was the car doing it before you had the turbo done? Or is it a new thing?

[Alex121]

Originally Posted by malteser

All good here Alex sorry for late post been moving flat lol

Was the car doing it before you had the turbo done? Or is it a new thing?

Hiya Danny,

Glad you're well Yep, the car was doing it before the new turbo and new TCV. Something isn't right. It did it again this morning, just the once.

The strange thing is, is that it always does it at around the same point of my journey, I do a lot of hard driving down the country roads once the engine is warm, then join a main road about 30 minutes into the drive, so normal driving resumes with traffic, then I take a roundabout to join the M3 and that's when I notice I've lost boost - Always after hard driving then 10 mins of calm driving. It's very strange!

[DXMachina]

Originally Posted by Alex121

The thing is, is that it always does it at around the same point of my journey, I do a lot of hard driving down the country roads once the engine is warm, then join a main road about 30 minutes into the drive, so normal driving resumes with traffic, then I take a roundabout to join the M3 and that's when I notice I've lost boost - Always after hard driving then 10 mins of calm driving. It's very strange!

I've seen extremely similar symptoms with both of my Mondeo TDs (Yes, I really am comparing an 89bhp paraffin-burner to a thoroughbred petrol turbo.. because its a turbo-car specific issue)

It was caused by a small valve on the fuel pump which opens to increase flow rate when the turbo comes online at (in that car) 1600rpm. Fresh from cold it worked fine, when fully warmed up it worked fine if constantly adjusted. After 10 mins of driving at a steady throttle setting it would stick and when I next opened the taps nothing would happen

(As opposed to something slowly starting to happen in an only moderately interesting way, which is what Mondeo TDs excel at)

So does the T4 fuel pump have a valve that opens with increased boost? possibly solenoid controlled? A new solenoid fixed both my cars when it occurred.