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In true STW fashion I have an 07 plate Audio A4 Avant, 2.0L TDI 170 S-line.
At about 60 MPH when I've gone from 4th into 5th gear the glow plug engine management light illuminates and the car goes into safe mode with a significant loss in power. It doesn't happen all the time, but often enough to start pi55ing me off.
The EGR valve has been replaced and on the most recent occasion there were no fault codes registered (a previous code related to the boost valve, or some such). One garage said it had something to do with how the cambelt was fitted at it's 80K service - I think it might be something to do with the turbo but I know FA about cars. I've got it booked in at a new garage next week but all previous ones seem clueless to diagnose the problem.
What's going on?
Cheers.
Ooh! Ooh! I know!
Maybe the wastegate is stuck! Stuck open could result in you not getting any boost pressure. Stuck closed could cause you sever problems with overboost. Best to get it checked I reckon!
(I love it when something you learn immediately comes in handy. Like learning the word "syzygy" on University Challenge and immediately using it as an answer on Only Connect)
Could be a heap of things to be honest, those symptoms are not overly helpful! This is the problem with modern cars - the PCM is pulling the power for whatever reason it sees fit, you need to connect to it to find out why it's unhappy, as it can probably detect and error long before you'd notice it manually. If you're anywhere near Glasgow I can lob it on my diagnostics box and drag the code off for you.
16stonepig - cheers, sounds like it could be something along those lines.
coffeking - again thanks, I live way south from you but thanks for the offer. I took it to a garage within an hour of one of these occurrences - matey connected his thingy-me-jig to it but no fault codes were registered?
Bear in mind that I only bring that diagnosis up as it's what happened to mine yesterday...
I'll go out on a limb and stake my reputation on partially seized vanes in the vnt turbo causing overboost. You can try innotec on car chemical treatment - has reasonable success rate depending on severity of carbon fouling or it's new turbo time ( approx 1100 inc vat fitted ). Avoid recon turbo units like the plague - not had long term success with any I've had dealing withs in the past. Get ecu fault codes checked at a vag specialist as first course of action. Turbo problems are unfortunately very common, we see approx 2 a week (independent diagnostic specialist).
coffeking - again thanks, I live way south from you but thanks for the offer. I took it to a garage within an hour of one of these occurrences - matey connected his thingy-me-jig to it but no fault codes were registered?
It should be checked with live data as it happens if no faults are recorded.
I'll go out on a limb and stake my reputation on partially seized vanes in the vnt turbo causing overboost.
This was my thinking based on the circumstances but I didn't want to suggest the most expensive fault to begin with lol.
Our passat was doing a similar thing last year and didn't give a code the first 2 times it was tested. Turned out to be a dicky crank/engine speed sensor. Could be anything though as said above, you need the code. Good luck.
saracendan - per chance, are you anywhere near Bristol?
Nope - but if you venture into deepest darkest Norfolk anytime soon let me know! Thetford forest has some ace (but flat!) singletrack!
You can buy fault recorders quite cheap:
Search U380-Diagnose-Tester-Diagnostic-Scanner
Saw Edd on WheelerDealers using one.
Bought one as my wife's car lurched the injectors due to a faulty low-pressure pump - didn't know it was faulty until it failed...
I have just become aware of the "Italian Tune-Up"
Given that I tend to not rev mine much above 2k, I wonder if a good blow-out would help now and again.
Given that I tend to not rev mine much above 2k, I wonder if a good blow-out would help now and again.
Universally helps, even if there's nothing wrong with it.
I had a Boost Pressure Sensor fail on my Passat recently with similar symptoms (except no light came on). Did produce a "too much boost" fault code though.
Guy in Bosch service centre at Caernafon sorted it (we wos on hols). Did did talk about coked up turbo vanes as a possibility too.
had something like that on my 02 honda civic diesel. turned out to be a partially blocked fuel filter. try that first. worked for me as the engine was fuel starved and lacked pressure in the fuel rail, hence shutdown.
thankfully a simple fix.
How hard are you trying when it goes? Full throttle, very light etc? Turbo vanes are certainly a possibility. When this happened in my t5 it was a turbo fault caused by oil in the fuel filter due to dodgy injector seals.
To find this out I had to buy a £30 ebay VAGCOM machine that I could leave plugged in and get the code as the fault occured as it kept not storing the code.
Mass air flow sensor? Any garage should pick this up though. When it goes limp is it completely gutless, or just above 1500 or so rpm?
If it's completely gutless you could try disconnecting the maf sensor to see power is more consistent.
New sensor should be in the region of £50.
^^
MAF was going to be my bet too (if it was a 1.8t i'd be saying MAF 100%!)
Jiggle valve or briffalator rods thats my stock answer.
Alot of the 2.0 tdi VAG engines have a problem with the oil feed to the turbo getting blocked, there is a modified pipe now. But wouldnt bring on a glow plug light.
the 170 has a dpf - is it the dpf light that is on? The Italian method or a good thrashing on a regular basis would keep that at bay.
Take a look on Seat Cupra dot Net - there are some really knowledgeable enthusiast on there and as the engine is shared across the VAG range you are sure to find the cause.