406 Hdi intermittint bad idle/ surging on low power

[patrickgledhill]

Hi guys, my 406 hdi has developed an intermittent lumpy idle, sometimes very lump lasting a couple of seconds,its kind of hunting noticeable both hot and cold.
ive put a can of very expensive diesel egr cleaner through no real difference, Also have some injector cleaner in the tank.

with the foot flat it powers away smoothly no problems


EDIT : Ive noticed that the car is surging on light acceleration, sometimes very jerky, once the foot is down shes happy

have may people had diesel pressure regulator issues? what do i look for in PP2000?
Also is it worth replacing the filter and housing?

Video below of idle and PP200 results

Cheers for any help

Patrick

[Gibbo_Wirral]

Have you tried the components testing feature in Planet? How about reading the data from reference values - such as the coolant, diesel and air temp sensors.

[Peter.N.]

Most likely down to an injector or low compression on one cylinder, if it settles down I wouldn't worry about it. The 'hunting' effect you have on tickover I had on my C5, it would come and go eventually it went and shortly afterwards became difficult to start, eventually I had to replace the HP diesel pump. It was down to low rail pressure.

Peter

[patrickgledhill]

Hi again, Thanks for your input Gibbo and Peter, i went and plugged the pp2000 earlier this evening and came back with some numbers. pictured below are parameter measurements at different revs.
i also had the error code pictured there aswell.
Peter its not hunting as such just on idle it had what feels more like a slight misfire, causing the car to judder a little. The needle is unsteady on first startup

Cheers again

[Peter.N.]

You will need someone who has a Lexia that works to interpret those figures for you.

Peter

[Gibbo_Wirral]

Everything looks nominal on those screen shots.

I'm assuming the MAF error is because you unplugged it to squirt in the EGR cleaner?

[patrickgledhill]

hah yes, that would have caused it!
do these correction figures cover whats achieved in a leakdown test?

is there any other testing that can be down fairly easily? i hear a knock every now and then so i should check the engine mounts.. could this be related? lately i have heard the knock or rattle under acceleration (definitly not coming from the motor)

[patrickgledhill]

Alrighty, after having the camera out videoing start-ups for a few days i managed to get one that shows the car actually stalling. I am noticing more now that under gentle acceleration the car isint smooth, power comes on and off making it quite jerky at times. The car starts fine.. hot and cold the issue is apparent.

this is the video on YouTube " onclick="window.open(this.href);return false;

EDIT:

Thought id make a video of the parameter while startup and idle as well
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cheers guys

[patrickgledhill]

ok ive made some progress, thought id unplug the egr and see what happens. well the idle has smoothed out and it seems to be driving fine but i will give it a few more days with it unplugged just to see if thats the only issue.
with the egr plugged in i put my finger on the shaft of the egr and it was opening and closing. does anyone know what this indicates?
vacuum issue? dirty egr? solenoid problem?

Cheers

Patrick

[Peter.N.]

Try running some EGR cleaner through it.

Peter

[patrickgledhill]

Hi Peter, yes that was the first thing i did. yesterday i had it off and cleaned it up good. However the cleaning had no effect. with the erg plugged in it still opens and closes on idle and while under slow acceleration (giving that surging sensation). I swapped the solenoid with the turbo one and no difference. i'm thinking either vacuum leak or the ecu is trying to tell the egr to do funny things... so ive left it unplugged.

The car is still experiencing intermittent power cuts under low power. fine on the open road. i replace the pressure sensor last year on the common rail so might unplug that and see what its like driving around the fixed pressure limp home mode.

cheers guys

[Peter.N.]

Strange that, I have been fortunate in not having odd problems with mine - yet! although it has for sometime been running in limp home mode but it doesn't bother me as I rarely exceed 2000 rpm or 60 mph.

Peter

[patrickgledhill]

yes the car stalled itself today at idle. ive unplugged the diesel pressure sensor and all seems well so far. its not actually too bad to drive around in limp home mode.
I'm interested to know what limp home mode actually means. I understand that the diesel pressure is limited but what else. Does unplugging the sensor and it driving fine necessarily mean that its that sensor or could it be one of many.
I hope that made sense.

Cheers

Patrick

[Peter.N.]

I think its mainly a rev limiter, mine wont pull at over about 2500 rpm which is no problem unless you need to overtake quickly - which I don't often.

Peter

[patrickgledhill]

Ok ive driven it quite a bit now with the diesel pressure sensor unplugged and it is smooth as. not problems at all.. apart from it wont go fast!
does this mean the sensor i purchased last year was a dud?

Cheers

Patrick