Boost issues.

[Jas11n]

Thanks for the feedback guys.
Fitted the new MFTS today and as suspected..........no change.
Waiting on the new knock sensors arriving and I'll test the wastegate diaphram tomorrow with a vacuum pump down at my local specialists (just incase the caps full of hydrochloric acid or something, knowing my luck at the minute )

[europeanme]

the smoke is black....it builds up pressure to 1.3-1.4 bar and then the over boost kicks in....on the off chance I get chance to change gear there is a ploom of black smoke..not really thick but enough to scare the hell out of me....when I am cruising (virtually no pressure on the throttle) along it very occasionally, what I can only describe, as a 'flat spot' just before I push the throttle and then away we go....

I did have a few issues before the turbo coolant line was found to be perishing.....it almost "flutters" on WOT...I have since fitted all but one roose hose...the three way hose (sorry cannot remember which one... )

my exhaust is on it's last legs...OJZ on saturday...what about knock sensors??...as it can give it the full beans..sometimes just not very often...

[s2_bo]

Any more clues? Sounds like it could be something simple unless the turbo is already toast

[europeanme]

Cheers Steve.
Yup, these damn cars can test your patience at times.

your not wrong there.....

Just saved my turbo from coolant starvation and a huge repair bill and while it was being getting some TLC, fixed a water leak...new Roose hoses...homefry.....and runs like a bag of poop....before the water leak fix was overfueling ever so slightly...now it's like I'm in a ****in' die-sel....

sorry to hijack your thread....

[LHD_Kid]

You can check the WG diaphragm quite easily, do you have a vacuum gauge?

Hi Jase,

A man of your talents should be able to easily check the wastegate diaphragm....

simply put a length of tube onto the hose connector, suck out as much air as you can with your mouth and then block the hose with your tongue..... wait some seconds, maybe 30 and then pull your tongue off - you will know if it has kept vacuum or not....

Chris

[Fat Audi 80]

You have no doubt already worked this out, but I would suspect a catastrophic failure of a Motronic feedback component, due to the complete lack of boost at all. What that failure is, given your already exhaustive list of testing and changing is somewhat confusing though?

Best of luck.

[s2_bo]

Knock sensors can defo limit boost with out giving fault codes, i had this too and it ended up that both the cables were perished and the cable shielding was all exposed. As soon as they were replaced it was all fine again.

You can check the WG diaphragm quite easily, do you have a vacuum gauge? then just plug it in to the nipple on the top and suck air out of it. If it leaks you'll soon know, otherwise just take the bolts off and have a look that way.

Good luck in sorting it out!

Cheers.
Bo

[Jas11n]

Cheers Steve.
Yup, these damn cars can test your patience at times. I missed the camping weekend just gone because of this
Just hoping the knock sensors do it, only other thing I can think of is maybe a split wastegate diaphram.
If not either of those, I'm stumped and in a corner as to what to do?

[Fat Audi 80]

Sorry to hear about this Jase. You have obviously spent a bloody long time trying to fix this.

Unfortunately all the things I would have suggested, you have already tested or replaced. Let's hope someone can come up with some other ideas.

You have my sympathy.

Cheers,

Steve

[Jas11n]

Cheers Chris, I'd jumped the gun and ordered two new knock sensors in between posting and your reply.
Lets hope this cures it, cos I'm getting a bit fed up now

20nm is the specific torque amounts isn't it? I read that it's crucial to be right.

[LHD_Kid]

Last thought, knock sensors????? No codes pulled with these

on my 3B I had similar boost issues, and was a knock sensor, no code either....

You can get away with buying the front one, as it has a longer cable, fitting it and then fitting the old one to the rear if there is no change from exchanging the front one...
I would say it is worth buying one of them....

was about 60 quid from Pete I seem to remember....

Chris

[Jas11n]

I've held off posting on this as I've spent an inordinate amount of time using the search function cos this issue seems to get at all of us at some point. I've read literally hundreds of posts.

Symptoms.

Intermittent engine cut out, ie a total momentary engine cut rather than an odd cylinder missfire. At first I had no boost issues after each episode. Then the engine decided to cut out completely, just died as if I'd switched it off. No stuttering like you'd get with fuel starvation.
Sometimes the car if left for only 5 mins or even 5 days, would absolutely refuse to start. Turn off and retry saw it start no problem.

Last two times it's did this it's left the boost now pegged at 0.4bar max at all times.
No fault codes..............ever. Output tests confirm the function of all covered parts, injectors click away, the WGFV is clicking away like mad, same for the ISV and carbon canister solenoid.
After reading posts and the motronic manuals and my bro's experience with a similar issue, I initially suspected Hall sender. He had had momentary engine cuts, engine cutting out completely, non starts and boost pegged at 0.4bar. Hall sender change cured this.

So far I've replaced the following;

1/ Hall sender (G40) - new,
2/ Engine speed sender (G28) - new,
3/ Crank position sender (G4) - new,
4/ Fuel pump - new,
5/ Fuel pump relay - new,
6/ WGFV - new (even though old one seems fine)
7/ F5DP0R plugs x 5 - new
8/ Both POS's swapped for my spare new ones (although I seriously doubted it'd be these two anyway)
9/ My spare set of x5 OEM coils (again didn't think it's be these)
10/ MAF swapped to a known good working one (my bro's) and also used mine on his car, fine too.
11/ My MTM chips removed and OEM chips put back in,
12/ My spare known good standard ABY ECU ("non imo" if that makes a difference, my ECU is an immo version) .
13/ Altitude sensor - new (vag-com wasn't showing a problem with it while looking at it's value with the engine running).

I've unplugged the MFTS and this makes no bleedin difference at all. Ordered a new one to be on the safe side anyway. Water temp fine, fan cuts in at just over 90°C and I've never had an autocheck warning of an overheat situation.

ZERO boost leaks, I'd assume I'd need a bloody major boost leak to be pegged at 0.4bar at all times. I've a set of bungs and the system holds pressure well. No audible sounds of air leaking (car has good condition hoses and vacuum lines and has the silicone reducer hose on the intercooler to crossmember instead of the O-ring (which was fine anyway, took me 10 minutes of twisting and pulling to get that apart)

Apart from the 0.4abr boost limit, the car has not cut out again, idles and drives very well but is still pegged at 0.4bar.

It's just not on being blown away by a bloody 2.0TDi Golf

Last thought, knock sensors????? No codes pulled with these and they are covered under diagnostics. although saying that, the damn Hall sender is and it never started crying to the ECU either.
I did notice a few times the car seemed to pulse a little under high boost and heavy load in a low gear and always put that down to crap 95ron petrol I had in at the time.

It's getting expensive now, worth buying two new knock sensors? If so, part number for an ABY as "KATE" is a little unclear with regards to one of them.

Sorry for the long winded post, but I believe it's best to give as much info as possible rather than the normal "Car got no boost..help"

TIA,
Jase..