Technical Engine issue

[Zekarn]

Hello,

I am trying to make my Doblo run correctly and am still searching on the issue that cause instability between a cold and hot motor (temps can be provided if needed)
After talking with quite a few people I have rule out any issue with pre-heat elements, fuel related issue up until the high pressure pump, battery, coolant, oil, blown head gasket, turbocharger and battery. Since Doblo aren't known for HP pump and injectors issues, I set that aside for now

My question today is what is the use/purpose of the screw circled in red and could it be related with my issue ?
I am actually replacing the MAF sensor (for the 3rd time btw, 2 open parts have been defective from factory IN THE SAME WAY, don't buy it from them)

Thanks in advance

Edit : the green pipe isn't unplug when I have my issues, I had unplug it to try to better see if I can remove the moving parts below witout removing the whole pipe

 

[bugsymike]

It may help if you tell us what the symptoms are.

 

[Zekarn]

My symptome is some instability at idle while the engine temp is between cold and hot
And that it shake the whole car
Unfortunatly I have no more informations than that

 

[Greasytrucker]

So once it warms up it’s fine and the erratic idle stops?

 

[Zekarn]

Yes, exactly

 

[Mike1alike]

What you circled is not related to your issue, that's the screw on the collar holding the air duct I would say.
Do you have a diagnose tool?

 

[Zekarn]

Yes I use MES but I don't have any fault code
And it don't look like a collar as it enter directly the metal duct. The collar is bellow, his screw isn't visible on the picture

 

[Mike1alike]

Do a graph with lambda sensors voltage, engine running on idle.

 

[bugsymike]

Air in fuel or EGR partially stuck open?
I assume well beyond heater plugs and cold start area?
Any smoke and if so what colour?

 

[Mike1alike]

And it don't look like a collar as it enter directly the metal duct. The collar is bellow, his screw isn't visible on the picture

And yes, I see the collar's screw now that you've mentioned it.
But the circled screw looks like part ot some spring clamp sitting there, above the collar. Not related to the problem, I'd say.

 

[Greasytrucker]

Air in fuel or EGR partially stuck open?
I assume well beyond heater plugs and cold start area?
Any smoke and if so what colour?

I was thinking EGR related

 

[bugsymike]

I was thinking EGR related

The early ones could be blanked off without causing error codes and ran better.

 

[Zekarn]

Do a graph with lambda sensors voltage, engine running on idle.

I will do the graph for tomorrow

Air in fuel or EGR partially stuck open?
I assume well beyond heater plugs and cold start area?
Any smoke and if so what colour?

Air in fuel is possible as I don't have the knowledge yet to check it but since I have this issue since I buy it almost 2 years ago and that I have done ~35000 km with it I believe it should have vanished ?
I had test EGR, blocking the air with a thin sheet of aluminium but it doesn't change anything except a fault code and an engine light on the dashboard
Yes it is well beyond cold start
No smoke most of the time and when I have some it is thin white smoke

And yes, I see the collar's screw now that you've mentioned it.
But the circled screw looks like part ot some spring clamp sitting there, above the collar. Not related to the problem.

Thanks !

 

[bugsymike]

I will do the graph for tomorrow



Air in fuel is possible as I don't have the knowledge yet to check it but since I have this issue since I buy it almost 2 years ago and that I have done ~35000 km with it I believe it should have vanished ?
I had test EGR, blocking the air with a thin sheet of aluminium but it doesn't change anything except a fault code and an engine light on the dashboard
Yes it is well beyond cold start
No smoke most of the time and when I have some it is thin white smoke



Thanks !

Air can keep coming in from things like leaking fuel filter etc and iuf small will clear after a short distance , but be worse if left standing for a few days.
I assume it doesn't have DPF at that age?

 

[Zekarn]

Oh, ok. It does not look worse after standing for a few days, in fact I had the issue less than 6 hours after doing ~1000km with my doblo. Fuel filter is new, fuel line from the fuel filter to the HP pump is new too (it was in bad condition when I buy it) and return line from the injectors was also renewed a few days ago (also bad condition). All parts came from Fiat except the filter
No I don't have one, DPF was only for 120HP version for this generation as far as I know

 

[bugsymike]

If white smoke and hard to start but clears as engine warms up then possibly low compression causing unburnt fuel. does exhaust bwhite smoke smell of diesel?

 

[Zekarn]

I don't have issue at start and the white smoke appears only when I have someone behind me with lights on. I don't smell diesel when behind it stinks a lot (smell like exaust gaz but more than other cars)
I wish I could take compressions on it but I don't have the knowledge nor the tools to do so. My dad have booth of them but don't have time or place to do it unfortunately

 

[bugsymike]

I don't have issue at start and the white smoke appears only when I have someone behind me with lights on. I don't smell diesel when behind it stinks a lot (smell like exaust gaz but more than other cars)
I wish I could take compressions on it but I don't have the knowledge nor the tools to do so. My dad have booth of them but don't have time or place to do it unfortunately

Generally white smoke on diesels, if smelling of diesel is unburnt fuel caused by low compression or if only just started then heater plug fault and it will smell of diesel.
These smoke tests can be done with car stopped and someone bringing the revs of the engine up whilst you check the exhaust smoke.
If the white smoke is real;ly choking but doesn't smell of diesel then it points to a DPR fault trying to do a Regen.
Apart from that if black smoke it points to excess diesel or not enough air/oxygen from the turbo.
If "blue" smoke and smelling of engine oil then usually piston wear.
The only other white foul smelling smoke I have ever seen was over 50 years ago on an Alfa Romeo Guilietta with a faulty brake servo which drained the brake master cylinder into the servo and the vacuum sucked it into the cars inlet. Servo design is different these days so unlikely to be that.

 

[noDi]

I've had some similar problems with a stilo jtd, do an injector leak down test, easiest to do with 4 syringes on the injector fuel return outlets, google it. Also, if you have mes or alfaobd, log fuel pressure, my hpfp was struggling to keep up on idle when cold but when hot it got pretty much normal.

 

[Mike1alike]

The only other white foul smelling smoke I have ever seen was over 50 years ago on an Alfa Romeo Guilietta with a faulty brake servo which drained the brake master cylinder into the servo and the vacuum sucked it into the cars inlet.

Wow! That sounds... thrilling!
You should have done drifts with the car in that state!