Turbo issues and someone to diagnose?

[HuwSy]

Hi, my S2 Avant (ABY) has some form of turbo issue going on. Mainly it's not providing any noticeable boost or making its usual whistle. Iv tried vagcom and it said no faults, Iv tried a couple of other bits and looked for various leaks but couldn't spot anything obvious. The garage here supposedly plugged it in and decided the MAP sensor was faulty but then when I asked where that was located they identified the temp sensor on the plenium chamber and gave the part no for that sensor. So I'm looking for someone who I can take this to diagnose who knows these cars better in the north west (Chester area if possible) Thanks

[UrS4boy]

The shop that you had your car in is cr@p. They're idiots. Run away and don't look back.

Here is some MAP sensor info:

http://forums.quattroworld.com/s4s6/msgs/20417.phtml

It's the black box with the red dot inside the ECU in this photo:

[Error404]

If you have no fault codes and no boost there are two common culprits, no.1 most likely:

1. The MFTS coolant temp sensor (Brown 4 pin plug under the water manifiold) the pins corrode and short out giving the ECU an ever-temp signal and it cuts active boost control - unplug this and see if you have your boost back

2. Knock sensors - these can go bad and give false knock signals so the ECU pulls timing or cuts boost altogether.

I am in Staffordshire if you want me to take a look

[HuwSy]

Hi,

I couldn't see how to get to MFTS connector, it's too small a gap for my hand when the engine was still warm. Will try again in the morning. But reading what it does it seems to also control the dash temp gage which does seem correct (as I'm used to at least 70 deg once warmed and only reaching 90 in traffic) so I'm assuming that's not faulty?

As for knock sensors is there anything easy to check these? Or can these be upset by an oil change which happened aaround the same time as the turbo stopping?

I may take you up on that if it still persists past next weekend. Too busy before that to get much done.

[newsh]

The MFTS is Multi Function so can operate the gauge correctly but still send a bad signal to the ECU.

[HuwSy]

Hi. Tried pulling the MFTS this morning and no improvement. It looked slightly corroded but not that bad. The connector next to it with spades and no rubber looks corroded and will look into this eve.

[Error404]

The two pin connector next to it is the temp switch for the after-run water pump

[HuwSy]

That possibly explains why that is a little intermittant. Will clean that one up if I can get a crimp tool and new spade connector to it.

is there any way of diagnosing the knock sensors? Will they show in vagcom anywhere?

[quattrito]

I have similiar problem with my ABY Coupe, in beggining when its turned on it delivers me full boost (1.0 in aftermarket boost gauge) but when it goes more than 5k it just cuts off the boost and without turning the ignition out it just gives me 0.4 boost in gauge. Everything is ok if I don't go over 4.5 - 5k RPM or turn it off! Where could I look for reason?

[Greg_S]

Its most likely a boost leak so I would check your pipe work first and see if you are loosing air somewhere

[HuwSy]

I have had a quick look over the pipes and couldn't notice anything obvious, which I know is by no means a definitive but it's the best I have access to. Would I not still here the turbo spool and waste gate? Is there any way to force the N75 to a boosting state to test if it is electronic or mechanical or would that be too risky/destructive.

[Greg_S]

You can disconnect the n75 and you should get mechanical boost of 0.8bar max. If you have some bungs I would perform a leak test. It's a common issue on s2's. Have you put a silicone hose on the joint between intercooler and x member on the pipe that goes across over the top of the intercooler? It typically leaks here, also the throttle body hoses are prone to splitting.

[HuwSy]

Hi. I don't have anything to close this off or run compressed air until next month. Although might get some silicone hoses just to rule it out and should be easy enough to change over atleast in the interim.

[Rusty]

Where about near Chester are you? My in-laws are up that way, so could swing by next time I'm up?

[HuwSy]

Hi, just in Tarporley.