Problem solving time?

[ian_jemo]

Hi all

Just about nearly had enough with my car but I know you probably know what I mean.

My problem is with boost and it seems very temperamental. Sometimes boost comes in hard and other times it doesn't boost at all. So I have connected my boost gauge up today and have found that when all is well the car boost to about 17PSI, and the other times it stays on 5PSI and will not move.

I'm presuming 5 PSI is mechancial boost. Does anyone know what can be causing this problem or anything I should test?

It happens about 50% of the time! And is starting to drive me mad

Thanks

Ian

[merlin's S4]

Dodgy wgfv?? Do you get any missfires or overboost protection as the ecu could maybe be going into limp mode? Are there any fault codes?

[Jamo]

Sounds like knock sensors.

[CliveH]

or Hall sender? do you ever have trouble in starting her??

[ian_jemo]

I have got one fault code and thats 2212 throttle Sensor, but I don't think this is causing the problem.

The WGFV is practically new. I do get a slight miss fire but this is only sometimes its nothing major. I don't know why but if I floor it in first gear the car hates it. It revs up ok but really sounds like it doesn't want to do it. I do get a few bangs out of the exhaust from time to time from unburnt petrol but no major misfires.

Where abouts on the car are the knock sensors. Could it be just a loss connection or do you think they might need replacing.

Thanks

Ian

[Jamo]

They'd need replacing, does the below sound identical?

I had exactly the same problem - it kept getting worse and worse.

It would boost to 1.4 -1.5 bar then after a few minutes cut right down to .5 and not go any higher until engine restart.

I also replaced:
WGFV
MFTS
ARS
etc etc..


Turns out it was the knock sensors.

I replaced them both (one had completely bare cable showing.)

Now its fine again.

I would try that if i was you.

Good Luck.,


Cheers.
Bo

[ian_jemo]

Jamo looks like you might have saved the day once again.

I have practically changed everything on the car so knock sensors could be a possibility.

Where are they hiding on the car? Might check to see if they loose.

Thanks again

Ian

[ian_jemo]

As its two sensors are the sensors the same. As seen here on Vagparts

Take it I need two of these

[ian_jemo]

I got the part codes gonna give vagparts a call tomorrow.

Parts Numbers if interested are 054 905 377G (ABY) & 054 905 377A (3B).

[S2central.net]

I think there are actually different numbered knock sensors Ian - the connectors are colour coded for one thing and sensitivity might be different on them - I don't know for sure. They are screwed into the block underneath the water rail - right PITA to get at really but not too bad. Do NOT overtighten them.

I have often wanted to wire up a knock sensing indication light off these - I have a circuit for one with adjustable sensitivity - just one of those jobs that never gets done.

Paul

[CliveH]

I have often wanted to wire up a knock sensing indication light off these - I have a circuit for one with adjustable sensitivity - just one of those jobs that never gets done.

Paul

Great idea Paul - any details?

[ian_jemo]

I just fitted the knock sensors onto my car and it has solved the problem.

Drove it for about an hour and it boosted fully every single time. Non of the on/off boost I was getting earlier.

Its taken awhile to get my car running right but know that it is, I'm loving it. Thanks to all the help, couldn't of done it with out you

[Jamo]

Heh Ian return the favour and fix mine

[s2_bo]

Thats Great news Ian! - Im glad you got it sorted Did you have to move the PSP to get to the sensors with out stripping your knuckles?

@ Paul, thats a great idea about a knock indication light. - my friend did this in his saab and now he just has a LED by the boost gauge constantly flickering

Cheers.
Bo

[ian_jemo]

It was abit tricky and did take some patience.

The only things I removed were the radiator cover and the PCV valve as I found this made it easy to get to the bolts.

Both sensors were pretty rusty and one was practically falling to pieces. Can’t believe the difference it made.

Cheers Jamo, sounds like your having a few probs at the moment, good luck tho as I know this cars can be a pain in the butt