'97 TDi 110 (AFN) not boosting?

[BadgerBoy]

Update - The problem is now sorted and turned out to be a lot more simple (and a hell of a lot cheaper) than originally suspected. If you're having similar issues, might be worth your while reading the whole thread to get some different ideas as to what your problem might be and how simple the solution could be.
BadgerBoy




Hi all, hoping you can advise!

I have a '97 TDi 110 with 150,000 that has suddenly lost power. It has seemed a little down on power for a while and just put this down to general wear and tear but there was sudden big drop in performance yesterday. Seems ok'ish to maybe 2000rpm but then, just as turbo would normally really be starting to pull, there's nothing. The engine is running as smoothly as ever and will rev cleanly when not under load but not when driving.

I've searched these threads until my eyes are square and concluded it was likely to be either the Air Mass Meter or vacuum hoses. Have checked hoses as best I can and they all appear in good condition and I tried a new Bosch Air Mass Meter but this made no difference.

Thing is, mine is doing something slightly different/not mentioned in all the other threads I've seen and I wondered if this might give any ideas:

If starting from cold, starts fine and idles at 800rpm immediately but if I start from hot, revs immediately jump to 2000rpm then drop to idle at 800rpm straight away, almost as if I'd started with my foot on the accelerator then removed it.

Also, I'm sure I used to hear a slight hiss/whoosh when I put my foot down (assumed this was just excess boost being dumped and can hear similar on my mates PD130) but can hardly hear this now and not at all after 2000rpm, just as the power drops off.

Oh, and my diagnostics socket does not work! Presently in process of removing centre console to check wiring but would really appreciate it if anyone has any ideas about the poor running?

Thanks
BadgerBoy
Getting greyer by the minute...

[calum]

First thing I can suggest is to sort the diagnostic socket . Do you have an aftermarket head unit in the car ? if so there's usually one wire that connects to a wire that it shouldn't , called the K wire , this results in the diagnostic socket not working . Do a search on this , it should come up with something , hope this helps you along the way ,

Other thought's , revs jumping when starting from hot but not from cold , have you changed the coolant temperature sensor yet ? Calum .

http://en.allexperts.com/q/Volkswage...-Wont-Smog.htm

[BadgerBoy]

Calum, many thanks for your quick response.

The car still has the original head unit though I've only had it 4/5 months (previously had another for 5 years that the cambelt went on after a cowboy supposedly changed it 8000 miles previously...) but judging from previous owners, I don't think it has ever been swapped.

Coolant temperature sensor has not been changed but could this cause the lack of boost/power? The revs jumping on a hot start has only just started happening, same time as the power loss, so the two symptoms do seem related but the temperature gauge is still sitting dead on 90c.

Thanks again, at least you’ve given me a direction to start looking in. Any other ideas appreciated though!

[calum]

On second thoughts , with the revs jumping up on hot starting but not on cold starting , could this be because of a split inlet hose somewhere ? My reasoning , a hot inlet hose will be much more pliable and more prone to leaking than a cold inlet hose . I'm referring to radiant heat from the engine affecting them , nothing to do with coolant temperature .

You could do a visual inspection of the inlet hoses but I'd recommend taking them off for a thorough check , flexing them against the bends to uncover any leaks / splits also check the o rings and of course the intercooler ,that's all I can think of just now , hope you come across something , Calum .

[ini]

When you hit 2000rpm onwards do you have excessive smoke?

Can you hear the turbo spooling up at all?

From your description it sounds like your turbo is not working.

Possibly the turbo variable vanes are jammed open in high boost position - check that the actuator rod moves freely on startup (needs 2 people), or by moving it by hand - 2cmish movement, its quite hard to pull against the spring.

Also suck on the control tube to the turbo actuator capsule to ensure the diaphragm is holding vacuum.

Or the N75 boost control valve is not functioning - test by blowing through it when energised and also when inactive, and lube with wd40 etc.

[hongkongstuey]

cheapest thing to try is do all the vacuum hoses with 3mm inside diameter silicone from demon tweeks or similar, the standard ones have probably been on since 97 and mine were cracked and perished. i had to change my coolant temp sensor on mine too, didnt turn out to be what i needed but was a pain to fit, right at the back of the engine bay, sounds like it may be that with the idle problem if it doesnt know wether its hot or not, whats the dash temp gauge saying?