I was that chuffed at being able to drive the car again after changing the duff HP fuel pressure sensor, I omited to say that it was still rather sluggish at low revs, However, in the hope that it may help someone else, I can now say that I believe I have found out why this is as well. Some or all of you might know that the turbo has a set of variable nozzles at the turbine exhaust gas inlet, which open and close depending on load, to vary the air delivery. I noticed today that as soon as I started the engine and ran it at tickover, the actuator which varies the nozzle geometry started working, and operated to about half stroke, and thus, at tickover, altered the nozzles, either reducing the velocity of the exhaust gas over the turbine blading by opening, or, by only
operating half stroke, did not close the nozzles sufficiently . It appears the end result is a reduced air inlet flow. As a test, I pulled the vacuum pipe off the servo cylinder, went for a run, and had all the low end power back about as it should be . There was a lack of "Oomph" over about 35 to 40 mph, but this is to be expected as the nozzles obviously couldn't adjust to the load & speed, with the servo disconnected. On returning home and removing the Pierburg vacuum modulating valve
, which controls the blower operating servo, the valve appears
to be open all the time by the same amount (i.e. leaking and thus operating the nozzle control servo incorrectly), whether powered up electrically or not - so I guess another bill is coming my way for a new one.
So, to any of you experiencing low end power loss/smoke, this is maybe something else to check. I have not seen mention elsewhere of this possibility, so maybe this might help someone out of a quandry in the future.
- great tip on checking the function of the EGR valve, and well worth remembering - will certainly try that if the need arises. As for the other suggestions, the fuel supply side was the first thing I checked, with the filter being renewed, as I had suspected blockage there and/or water (though the water sensor should have operated the warning light if any present. I was leaving the fuel pump/injectors as an expensive last resort, and scrabbling furiously at everything else - which is how I found what I believe is a malfunction of the Pierburg modulating valve - but thanks for your (and everybody elses) input - what a great bunch of guys on this forum