Could be MAF, but not a typical case. Might be an EGR issue; but getting the codes checked is the wise first step. If there was a boost leak etc. it should have noticed.
If it's fitted with a rudimentary diesel cat, then that can't be ruled out either.
When was the fuel filter last changed? Winter DERV in the tank? No veggie oil?
Edited by Screwloose on 23/12/2007 at 19:22
|
|
Fuel filter was changed about month ago , I only use BP diesel , the change in power was instant so it isn't the cat , whatever it is has failed or almost failed quickly.
|
My 02 TDI 100 went in to a low power mode 6 months ago after I switched off the engine at a queue for road works. It came back to full power mode a few miles later .
I had a diagnostic check done. I did not get a fault number but the verbal report was related to something allegedly blocking the air intake - not satisfactory for the £50 I know. No problems/blockages were found on a visual inspection.
Problem has not recurred in the 9000 miles since . I had the EGR assembly changed recently due to an oil dribble. 108,000 miles on clock now.
Not helpful to you I know.
|
|
|
|
Ok I now have a scan code thanks to my trusty US vagcom software, it says
17964
Charge pressure control: Negative deviation : P1556-35-10 intermittent
I don't know about the intermittent part but the vehicle was like this for 2 hours, it seemed to be in some sort of survival mode. The engine ran smoothly enough and ticked over but the throttle seemed limited to a very small amount , flooring it made no difference to the speed.
|
Stuart
Strange that the MIL didn't come on; you were in limp-home mode, flagged by one of the evil twins - 17964 and 5.
They come in two flavours, but you've got the underboost one. Basically; the ECU knows what boost to expect and when it doesn't get some, it defaults to limp to save the engine.
Many causes; boost pressure sensor; "N75" turbo control solenoid; it's vacuum hoses damaged or perished; or the nasty - the VNT turbo itself - coked-up. 17964 can also be caused by a split intercooler or a leaking turbo hose.
You'll need a good man to test for:- leaks, the thrust sensor, the vacuum system and the smoothness of movement of the wastegate actuator - a really good one might even de-coke it for you if necessary.
|
|
Thanks for this , I will check out the obvious things myself , I doubt the VNT is cocked because of the immediateness of the fault , I have just done the cambelt so if I am lucky something may have got disturbed , after the festive season I will drop the floorpan cover and have a look around
|
If the vanes of the VNT stick; the ECU will notice the low boost and drop to limp in an instant.
There's little that you can do yourself, beyond checking every inch of the vital vacuum hoses, unless you have the equipment to physically test the components. [An oscilloscope; a Mityvac and a good meter.]
|
Problem solved!!!
I decided to tackle what I could on my sick Passatt. Started by removing the plastic engine cover and immediately discovered a hole in the vacuum pipe to the charge overflap actuator. I decided to check a few other things like the air filter whilst I was at it , I removed the ducting to the air box and the cover plate and guess what more vacuum pipes with holes in . The main one being on I think the line to the charge pressure solenoid. The lines have been chaffing on the bottom of the airt ducting and the engine plastic cover. I suspect the lines have been disturbed in servicing , some of the ties cut off and not replaced leading to them rubbing on bits they are not supposed to touch. I replaced all the damaged lines and used cable ties to ensure they now can't rub. Low and behold the power was back , much more than I remember , plus as a bonus no black smoke!! I suspect I lost emmision control slowly as the pipes leaked , then a big enough hole in an important one shut the turbo down.
|
Nice going. Any vac leak anywhere and the control solenoids would be switching fresh air.
I know plenty of garages that would have started by changing the turbo for that code and would only have checked those vital hoses after it didn't work. A few metres of vac hose costs a lot less than a VNT.....
|
|
Well done stuart and screwloose, a happy ending for a change.
|
|
|
|
|
