The engine installation is a bit odd, it has a Digijet computer but it has the Digifant style modulated air bypass idle control (VW 251 907 393) as opposed the usual idle stabilizer (VW 251 906 083).
The idle controller is faulty so someone has “fixed” the idling by winding out the idle screw to compensate. An upshot of this is that the throttle position micro switch is open at zero throttle, but is closed correctly at full throttle.
You have to apply a bit of throttle to start it and hold it on the throttle until it warms up a little, but it starts on the money every time. Once warm, idles nicely at about 800rpm.
The ignition timing is set to 10’ with no vacuum connected. The centrifugal advance cuts in and out at the specified RPM. The vacuum advance and retard both appear to function correctly.
The fuel flow rate is good and the fuel pressure is as specified 1.8Bar and 2.5Bar with and without vacuum on the fuel return valve respectively. The injectors all seem to be working fine but no flow test has been done.
The water and air temperature sensors are within spec as is the air flow meter resistance. The air flow resistance varies as per spec with no noise or dropouts (i.e. no Vanagon syndrome)
Dizzy cap and leads are new. Earths have been cleaned. Filled with 98 or 99 Ron fuel.
The engine runs nice and smooth, doesn’t misfire, doesn’t cut out but unfortunately doesn’t rev above about 3000 rpm
When we got the van last year the power was so low that the kids and I had to push it up some hills while my wife gamely tried to incinerate the clutch in a vain attempt to keep the revs up. This was traced to incorrect timing, once this was sorted it became an absolute blast to drive
On its next trip out after about 30 motorway miles the power dropped right off (although not as bad as before).The engine is unwilling to rev. On a flat bit of road it will not rev much above 3000 rpm in third or forth rear. There is no “hard” rev cut off or cutting out, just no power.
Does anyone have any suggestions? I’m all out of ideas.
Many thanks.
