Engine: D5244: Ecm 6805 and boost related issues

[aland]

I had a spare MAF in the garage, so changed it. Showed around 35kg/h while idling.
No change to issue though, graph below showing when I booted it and it went into limp mode.
I forgot to add the EGR to it.
Air filter is about a year / 6000 miles old and is a little discoloured but not dirty. This issue pre-dates the air filter though!

@ Davebb - I don't see an option for requested MAP??

Same as before though - 1st boot after engine warm, limp.
Shutdown / restart a few miles later, then no further issues for the next 5 miles home. Surely air filter and most sensors won't care much about temperature / run-time, but sticking mechanical VNT could?

I'll do another graph tomorrow from cold. Can only add 5 parameters, so which ?

[davebb]

Hi it maybe newer cars that you can log what the ecu is asking for,
I would say that the car is over boosting at nearly 23psi of boost, the 163bhp should be max boost of 16-17psi,
has the car been re-mapped ? if not it is the vnt,
Like Simon said make the vnt move with vida, do it after a good run, so the car/turbo is nice and hot, and see if vnt is moving well,
Dave

[davebb]

Originally Posted by aland

Well that was short lived.
Last weekend there were no faults, no matter how hard I tried to provoke it.
Now we're back to the 'Engine Service Required' when booted and ECM-6805.
It's odd that it can be fine, then re-appear. I expect the turbo was HOT last week after several 'enthusiastic' drives, so maybe the VNT is sticking when cooler.
I'll blank off the engine mounts again to confirm that is (still) not related. There were no vacuum leaks anywhere when I checked last week with a mitty gauge.

May need to give in and remove the turbo to inspect it.

have another look at the pipe and make shore there is no leakes
this would show low mass air flow and can make the car overboost,
also have a look at the ally pipe that can crack were it is bolted on to the engine block,
Dave

[aland]

Thanks Dave.
It's not been re-mapped as far as I know, I've owned it from 3 years old, company car before that.
The turbo intake pipe (and ali pipe) have been swapped with an 'almost new' one from my spare engine, no change.

I'm assuming that the MAP sensor isn't lying - it's reading flat lines even though the rpm continues to climb - and I assume the turbo continues to produce more boost... Or maybe that's just the max it can register?
I don't have a spare MAP to try that unfortunately.
I do have a spare turbo though!

I notice also that the fuel pressure drops before it goes into limp - maybe that's the ECU attempting to reduce power?

[cheshired5]

Peak rail pressure is too high.

When was the fuel filter last changed?
Also, have you done the fuel correction test yet?

[davebb]

Originally Posted by aland

I had a spare MAF in the garage, so changed it. Showed around 35kg/h while idling.
No change to issue though, graph below showing when I booted it and it went into limp mode.
I forgot to add the EGR to it.
Air filter is about a year / 6000 miles old and is a little discoloured but not dirty. This issue pre-dates the air filter though!

@ Davebb - I don't see an option for requested MAP??

Same as before though - 1st boot after engine warm, limp.
Shutdown / restart a few miles later, then no further issues for the next 5 miles home. Surely air filter and most sensors won't care much about temperature / run-time, but sticking mechanical VNT could?

I'll do another graph tomorrow from cold. Can only add 5 parameters, so which ?

Hi
I don't no what you mean by the MAP sensor is reading flat, it is reading boost fine look at your log, it is going up to nearly 23psi of boost, on a drive, you need to load a turbo car to make boost pressure,
I think that your year sensor will read up to 3bar, so that is 2 bar off boost and 1bar the air pressure that we live in,
also a vacuum leak from any of the vnt actuator will not make the car overboost, as the turbo vnt actuator needs vacuum to operate, so if you take off the vac pipe from the turbo actuator you should only get low boost,
if you try this make shure that you block the rubber pipe that you removed,
also limp mode will come in if the boost is 400milibar higher than it should be
and that would take you to the boost level the you recorded on a drive,
Dave
Dave

[aland]

Originally Posted by cheshired5

When was the fuel filter last changed?

About 2 months ago.

Originally Posted by cheshired5

Also, have you done the fuel correction test yet?

No

Just grabbed another graph when all is well... same situation again, after 1 or 2 limps and resets it's then fine no matter how hard I poke it. Fuel pressure is in the same range as before when it went into limp.

This time the VNT does NOT flat-line at 95% - surely the only reason it was doing that is because it was over-boosting and the ECU is trying to reduce boost by increasing the VNT vacuum?
If it is sticking when colder, and not once HOT, the VNT control is then regulating boost as demanded and all is well.

I can't see how fuel delivery related issues etc can suddenly fix itself once HOT, but a sticking VNT could.
This engine has done 257k miles and the turbo etc has never been off.

[aland]

Originally Posted by davebb

Hi
I don't no what you mean by the MAP sensor is reading flat

I grabbed another graph of it going into limp. RPM only reached 3532 on that one.
You can see that both the MAP reading and VNT flat-line long before maximum rpm is reached, and then it goes into limp.
This is quite different from the previous graph when all is well, and they climb gradually, and rpm reached 4389.
(Added un-edited graph also to show peak values).

[davebb]

lower vacuum lower boost,
fuel pressure will be higher if the boost is high,
I will 99% say it is the vnt needs cleaning, but do test the vnt with vida when looking at it, hot and cold,
Dave

[aland]

Originally Posted by cheshired5

Peak rail pressure is too high.

Maybe by a tiny bit, but not much. The peak in my previous graph above is 1637300 hPa which is 1637.3 bar. As the D5 engine working pressure is 1600 bar (https://en.wikipedia.org/wiki/Volvo_D5_engine) then it's within 2% of what it should be!

In the 'normal' graph, with no limp, it reached 1681300 hPa, which is 1681 bar, or 5% above spec.
Not exactly wildly out.