[Engine] Smokey cold start and misfiring

[RobS]

Been working on this for some time and getting advice on a thread in the B59 section. As this is a B9 Multispace (2008) I have started this thread to continue. 

Background is car is the wife's we have had it about 4 years, I have been ignoring the problem!! Serviced it a few weeks back so all new filters, Oil etc. It was still embarrassing at cold start up tick over almost stalling loads of smoke. As soon as warm runs as good as gold. Then I had one of those great ideas "I'm going to fix this thing". "Ho yes" said Berlingo.

Tested glow plug heaters all open circuit easy fix!! NOT.  Fitted new heaters no change Berlingo one me nil. Fitted new glow plug relay no change Berlingo two me nil. Fitted EGR valve blanking plate no change Berlingo three me nil. Emissions warning light "on" no change Berlingo four me minus 1. Fitted new EGR valve removed blanking plate no change Berlingo five me back to zero as emissions light off, "Yes". 

https://www.dropbox.com/s/jakmg9hmr16h03...9.mp4?dl=0

Advised to get it hooked up to some monitoring. Invest even more money in a Diagbox and interface and spend a week getting it to work there is a complete thread all about it have a look, Berlingo Six me still nil. And that where we are now. 

I was beginning to think it wasn't ECU/sensors but an injector mechanical issue. But don't think it is now as in the mean time I have done a 3 cylinder cold start with each injector disconnected.  Four tests and each one no change in fact it is hard to tell it is running on three. Berlingo seven me nil, It must be over fuelling when cold.

[Sol]

There is a severe warning in the Citroen technician documents about not running the HDi with any injectors disconnected, as they can be damaged badly. Not sure why. It doesn't say why. I think it may be possible that peak cylinder pressure can shove carbon up the tip nozzles if it isn't counteracted by the high pressure fuel being injected out at that point, when the injector isn't connected.

Anyway have you tried a cold start with the MAF already disconnected? Make sure it has been off for a good few minutes before pulling the MAF plug off, then in the morning, try starting it stone cold with no MAF plugged in. I'm reasonably confident it will run perfectly.

My thinking there is the aging MAF using hot film resistors to measure airflow, has old resistors that have drifted and heating takes longer. So the resistance is higher, air flow looks higher as a result, more fuel is injected as a result, and it overfuels when cold.

Disconnect it and the ECU uses a default map value of 400 mg airflow at idle (the factory perfect value) and so, correct fuelling.

I mentioned trying this in your original thread, worth a go. It will trip the EML but not permanently.

[RobS]

Yes I did try the cold start with the MAF disconnected and it was still the same and it didn't put the emissions warning light on strangely. I will do that test again now as a have the ability to check for fault codes it should remember that fault.

[Sol]

You see when mine was doing that, I pulled the MAF while running live data on DiagBox and it instantly stopped smoking and hunting. I tried an EGR blank as it was cheap and easy and that cured it almost totally.

I did pull the MAF off while it was running badly and it slammed the EGR shut at that point, as it doesn't use EGR with no MAF. It ran smooth as can be. That meant I had two choices so tried the cheaper option and it worked.

I did note that even when smoking and lumpy, when the coolant hit exactly 50 degrees the whole thing switched to running perfectly even with no blank and everything connected. It is a weird fault. But, very common in this engine even on BMW, Ford and Mazda cars which use the same motor.

[RobS]

Had a go at it with the diagbox today spent a long time just exploring the thing. Loads of ecu faults in memory but that is to be expected as I was pulling all sorts of plug off. Cleared the faults and went for a drive the only fault then was egr valve position. Reset new part fitted egr valve, then cleared the faults and test drive. Now no faults at all, going to leave it over night and see how it cold starts now.

[Sol]

Interesting. Let us know how it goes.

[RobS]

Cold start this morning and the idle was steady at about 800ish on the dash so that must be one to me (or us) but it is still smokey and smelly. Maybe the two issues were not connected or maybe it's going to go back to erratic idle when it is real cold.

Next thing I need to do is learn how to capture live data from the diagbox. I did get some on screen yesterday but just looking at a load of number isn't much good if you don't know what they should be. Many thanks to the group members who have got me this far any one care to enlighten me on data logging and analysis ?

[Sol]

Run a global test first to gain access to individual ECU data, select the ECU you're interested in which then reveals a sub-menu including live parameters.
You will have the choice of Standard or Custom.

Standard offers all the relevant parameters according to category - Air, Fuel, Electrical etc.
Custom allows you to mix n match any parameters from all categories but is limited to just six at a time.

When you're happy with your selection, there's a box at the bottom that starts the measurement recording in the background while showing the live data list in numerical form. To watch the data live on a cold start, get the live data screen ready with the parameters you want to view, then start the engine and watch the data become real values. For this type of view when not actually driving then recording is not needed as viewing recorded data back, is not so easy. I did post about it in my original thread when I had this issue and posted graphs from Excel of the data.

I'd say you want to map measured airflow, EGR throttle (which is doser position), EGR position, fuel pressure, inlet air temperature, coolant temperature, injector corrections for all 4 injectors. Only 6 can be selected so look down the list and tick only the ones you really need as above.

For instance if 3 of the injectors are running -/+ 0.3 etc and one is -10 correction then that would indicate one is overfuelling. The ECU is trying to limit it with a big negative factor. For example.

Airflow should be around 400 on idle and fuel pressure about 290 bar again at idle. Don't touch the throttle so you see only the idle control values.

[RobS]

OK thanks I have ordered some Diesel Extreme Injector Cleaner so I will do some tests before and after. The issue at the moment is we aren't doing many miles so it will take a long time to run a tank of fuel with cleaner through it.

[RobS]

I have done some cold start testing and the air flow and fuel pressure at idle are in the correct area around 400 and 290. No injection faults were being reported and EGR seems to be working OK since it was reset. 

Never the less it is still diesel smokey / smelly at start up. I have put some injector cleaner in when filling the tank and we will see how it goes. That will take some time as we are not doing much driving at the moment.