Hello all, First post here and I am in need of some help. I got a 1996 406 2.0. On a light throttle the engine seems to respond OK but when I open the throttle it bogs down until the revs rise over 3000rpm. Being a semi skilled Alfa Romeo mechanic i have checked for the obvious air leaks etc but started getting dark and gave up, so thought I might ask here and ask what the common faults are to give such symptoms.
Lambda sensor replacement and full service is recorded in the service history within the last 10,000 miles
I have had the car over a week and I have fixed a fuel leak (from L Shape connector before the fuel rail) I also welded the pipe back on to the back box (rotted Away), fixed central locking (Key was spinning), I fixed a faulty fan motor (traced to a burned out block connector), Fixed the controls for the electric window on the drivers door and the list goes on.
I'm guessing petrol. 8v? 16v? 8v turbo? Very different units.
The only thing I can think of off the top of my head would be an air flow meter issue (16v engine only i think?). I reckon it's got to be something one of our resident pros have come across before, the symptoms are strange enough to be memorable
<steve_earwig> I think this forum is more about keeping our cars going with minimal outlay than giving our cars more reason to go bang
Do these engines rely on the map sensors as apposed to air flow meters, Alfa's common problem is Maf but cant see one on these engines.
It is strange, it now idles fine after cleaning the idle control valve, I can rev to the red line with no problems but as soon as the engine is under load it starts pulling back until i start reaching higher rpm. I initially thought i should replace the fuel filter, it did get a little worse since i fixed the fuel leak (maybe coincidence).
I presume it sparks fine so that rules out coil pack and plugs, It idles fine and still does it when cold so that would rule out lambda off the top of my head i cant think what else it would be.
To be honest I know very little about the engine and I'm not too hot in that area anyway. If it were me I'd check the HTs, plugs and gaps, then I'd tie a pair of tights over the throttle and disconnect the air filter box in case part of the intake is blocked/dislodged funny, then I'd give up and resort to a diagnostic check at the dealer
But only if I didn't get any help here from someone who knows what they're talking about (ie. not me!)
<steve_earwig> I think this forum is more about keeping our cars going with minimal outlay than giving our cars more reason to go bang
Hi there. Looks like it doesn't have a MAF so it must have a MAP (otherwise how does it know?) but the diagram just has lots of control units labelled "sensor" so I can't tell you where it is. The usual problem seems to be the lambda but you already replaced that
Dead reckoning? Well, I guess, all things being equal... I think the diagram had an air temperature sensor though and the obligatory pot but I don't know if it just has two contacts (idle and full throttle) or it is indeed a bona fido variable resistor.
Thanks for the replies, it is very reluctant under the 3000rpm mark, and starts pulling stronger thereafter. Most things that i can think of would cause it throughout the rev range or just higher up the revs.
It does sound like lambda symptoms, so i disconnected that and still the same.
Checked air filter and that's new, however the air feed pipe that clips to the metal bracket underneath the air box was loose (not the top part into the air box) the pipe has come away from the bottom where it gets the air feed, so i need to have a look at that. I seen a diagram that it has 2 parts.
Just an update, I think i may of found the problem.
You will notice on the first post i mentioned that i fixed a fuel leak, the fuel was escaping from a small L piece just before the injector rail. I fixed that and re clamped the hose. Now there is more fuel escaping from the fuel line, i could smell through the air vents.
So it got me thinking why i fixed this and it is still escaping and must be the fuel pressure is to high. I am now thinking the fuel pressure regulator is causing both the fuel leak, hesitation and rough running.
so I can't tell you where it is. The usual problem seems to be the lambda but you already replaced that 
