Technical Multijet high boost fault

[Cinq999]

I parked my 2005 MJ up for 2 weeks while I was away on holiday.

Since I've got back, it keeps on throwing up the high boost pressure fault code.

I thought at first it would be the normal thing, the wastegate actuator getting stuck.

However, the actuator moves perfectly freely. I've doused it in WD40, and worked it with a long lever bar several times, but the fault keeps on coming up.

Sometimes its when the engine is almost cold, it'll suddenly pop up and lose power......other times I can drive 50 miles no problem, then it'll suddenly happen.

Being that the actuator seems to be moving freely, is it possible that its the MAP sensor in the intake manifold that could be causing the issue?

Any ideas?

 

[koalar]

As a stating place try reading the atmospheric pressure with a scan tool should be roughly what google tell you

 

[Cinq999]

Checked barometric pressure, 14.4psi.....which I guess is about right.

It did it again today quite randomly.

Sometimes at low rpm when turbo just kicking in......other times at high rpm when the turbo has been under load for several seconds.

Checked the actuator again and put a load more wd40 on it.....moves smoothly, no hint of it sticking open or closed.

Took the map sensor off.....looks pretty clean.....but I suppose it could still have an issue?

 

[koalar]

I don’t have enough experience with the multijet
MAP failure is normally way off 14.4 sounds like the right ball park to me

 

[bugsymike]

I don’t have enough experience with the multijet
MAP failure is normally way off 14.4 sounds like the right ball park to me

I have a vaguely similar issue in a 2010 Doblo Cargo 1.6 Multijet, start off from cold with a little black smoke on acceleration, once warm on the ring road give it some boot and it loses vacuum to the wastegate (tested by a gauge) so lose boost then goes into Limp mode with overboost code. Delete it and off we go again.
On mine my thoughts are as EGR vacuum is activated when warm it is losing the vacuum to the turbo wastegate . Turbo is new as bought vehicle with loads of issues one of which was the smoke screen from the turbo seals! Tried reducing boost, made no difference.
I have other vehicles so only look at this problem when the thought takes me, due to lack of enthusiasm

 

[koalar]

Unfortunately not so many diesel pandas about. The same engine is the same in a lot of cars.

I was hoping someone else would have come along by now

Maybe posting in the 500 section ?

Blocked pipe ?

1.3JTD Turbo P0238 | FIAT Doblo

I've bought a 2004 Doblo which can't go faster than 110km/h because the turbo is always on. Engine light flashes one second and the car goes in limp mode. I've read a lot on this forum and it seems to be 'normal' that a 1.3JTD has this error. It can be a seized waste gate or the sensor. I...

www.fiatforum.com

Should be able to see if the actuator is working. Depending if it’s a normally open or closed type applying vacuum or pressure you should see it operate. Plus if it holds the pressure you know the pipe is okay

 

[Cinq999]

I've actually got a spare engine at work, and I'm fairly sure it's still got the map sensor fitted.

I'll have a go at swapping that over first, and see if it makes a difference.

If it still does it, then I'll try and get underneath, take off the rubber pipe and clean it out.

I guess I could use an airline at work and make sure the diaphragm itself is okay.....although I would of expected it to be more often if that was the issue.

I'll update on Monday once I've had a further look.

 

[bugsymike]

Just a thought, one of my daughters had a GTD VW Golf 130Hp, which would go into Limp mode occasionally, the code indicated "overboost". I traced her problem to a sticking VVT (variable vane turbo) due to her not having a heavy enough right foot , what was happening was the vanes in in the turbo were sticking in a half open position so when driving at lower speeds it was providing too much boost.
The cure was spraying "turbo cleaner" aerosol into the turbo via a sensor hole , then working the lever on the waste gate vigorously several times to ensure full movement in both directions.
What happened is due to high mileage a build up of carbon deposits jamming the mechanism.
You would need to check if your car uses VVT on it's turbo as my knowledge is general and not specific to Fiat.
I am sure you know, but diaphragm is vacuum operated so high airline pressure will destroy it.

 

[Cinq999]

I'm becoming more convinced this is a sensor fault.

I've just driven 50 miles, driving like a granny, changing gear by 3k rpm to make sure there's not too much boost.....and it was fine....but it's used nearly 1/4 tank of diesel.....which is never right.

I'm guessing it's massively overfueling constantly.

 

[DaveMcT]

Check the vacuum pump is properly doing its job and there are no vac leaks in the system. It might have enough umph for the intermittent use of braking but could be dropping too low to keep the turbo actuator happy.

 

[Cinq999]

Problem solved.

It was the short rubber pipe that connects the wastegate to the turbo.

Took it off, blew compressed air through it, and it was clogged solid.

Fitted a new piece of pipe and new clips, normal operation has been resumed.

 

[koalar]

Problem solved.

It was the short rubber pipe that connects the wastegate to the turbo.

Took it off, blew compressed air through it, and it was clogged solid.

Fitted a new piece of pipe and new clips, normal operation has been resumed.

Cool well done