406oc.co.uk

Hello you clever lot, I have a 53plate 2.0 hdi 110bhp, suddenly it's decided it don't like pulling away from the lights (either hot or cold), it don't have the problem all the time (prob only 20% of the time), starts easily and sometimes the tickover is like it's running on 3 cylinders, it's done 120K miles, had a new fuel filter and the EGR valve blanked off (which put the engine management light on in the dash 3 years ago) I have no method to check any error codes...............whatdya think?

I suggest you unplug the MAF sensor first, which is the grey rectangular one just off the air box, this will put a light on the dash but will go off again after a few days when it's plugged back in.
If your car is back to normal then it's likely to be the culprit - easily replaced with a new one but can be a bit pricey unless you wait for an ECP discount weekend code..
If the performance doesn't change then the MAF isn't at fault, then it may need diagnosis - but in the meantime use some posh super diesel and drive the car a bit harder than usual to try and clear the injectors...

Thanks Ging, I'll pull it off tomorrow

I remember why I hate cars!..................I can't get the 'flippin' connector off.............any tips?

Err, is it one of those connectors with a wire clip? You push the wire clip into the connector and it should just pull off.

There's a springy tab on the connector that needs to be pulled away from the sensor body, (i.e. downwards), to allow the plug to slide out of the connector housing, (towards the engine).
Once you've done it once it's easy - stand beside the n/s wing, reach under the sensor, hook a fingertip or two over the tab and ease it down and away from you.

there is nothing on top of the connector, there is a thin metal finger on each side of the square plug n I can feel a 'lump' underneath, god knows what I'm supposed to do with the thing, but all I want to do is hit it with my sledgehammer!!!

Yes, it's tempting....

Look here - https://youtu.be/tT8yHXJCjJI - it's a video from one of our members ( Farmerpug ) and you can see at 2.20 into the video the little tab under the connector - sadly you can't see him unplug it but it might help a bit.

Sadly that video was about as much use as a kick in the................ I have just spent 30 mins trying to release that clip that's underneath (so ya can't see it), right now I want to pick up my beautiful sledgehammer.............. how you blokes can stand all the tiddle fiddling aggro working on these things I can't imagine, for me I'd rather stab myself in the earhole with a bit of 4x2!!!

Can anyone on here actually tell me how to release that 'flippin' clip that's underneath the connector???

Okay.
I no longer have a 406 do I can't do a quick video, but I'm pretty sure it's just a tab that you lift away from the connector (i.e pull it down towards the ground) and the the top grey bit should* slide off to the right, the black bit is part of the MAF and is fixed....
Worse case, you can lift the air box up in the air (it's not held in, just a snug fit) and you may get a better view.
Sorry but I can't even check for my own peace of mind, and sanity...

Doggy, you're a genius, I just want to pick you up n carry you straight down the pub! the only thing you forgot to say was ' get a knife out the kitchen drawer n use that to spring out the tab n then just withdraw with much joy n relief !'

So, I've got the MAF sensor unplugged, I'll give it a couple of days n then report back

A small screwdriver is what I usually use but a mirror is also helpful.

Peter

I spent 30 mins with a flat screwdriver, but the blade must have been too thick, I'm sure though that my sledgehammer is a perfect fit

Ginge..............it's been a few days and so far the car has lost it's hesitation problem so many thanks to you and everyone that helped me...............BUT..................sadly I still have another fault which is intermittent stalling/dodgy idle when slowing down. I'm guessing it could be the idle air control valve, but where the flippin eck is the sucker?

As far as I know there isn't one on the diesel engine - its all done by its many sensors.....

There is a brown switch on the clutch pedal that is designed to reduce the engine revs when you dip the clutch, its supposed to make the gear change smoother, I guess this could be broken or dodgy wiring.. Do you have Cruise control?

Also, there is a fuel pressure regulator on the back of the fuel pump, its a circular lump held on with 2 torx bolts - this can be gently removed ( if it won't budge then don't force it!! ) and if there is a filter on the end then this can be cleaned with carb cleaner or something..

Is the throttle cable too tight, this can play silly buggers with the revs on the over-run, maybe pop the clip off and move it backwards one ridge.

Have a look on Amazon for fuel system cleaners ( BG244, Archoil, Forte etc ) which may help in the meantime - about £20.

Thats about it as far as my mechanical knowledge goes, sorry...