Limp Mode

[Austineer]

Gents,

I have a few questions regarding the ECU limp mode as I think my car has been subjected to this on a few occations. This seems to be happening on random occasions i.e. both playing with the N75 & doing nothing at all to the car and its really annoying. The main symptoms which I have noticed are the following:-

a) General sluggish performance

b) Boost readings never change whether in sluggish or responsive mode.

c) When in sluggish mode at full boost (15 psi) seems almost gutless

d) Slower responce to throttle input regardless RPM, Boost or Engine load

After my recent playing with the N75 it happend again, though strangely it didnt happen with the N75J in, but only when I put the stock N75 back in. The car was like a snail of which felt even worse due to the fact of going down to the original N75 from the N75J. The car drove like a snail for 2 weeks then seemed to have a complete transformation whilst driving.

I was getting frustrated thinking to myself that this didnt feel like a 230bhp/250flbs car and took it for a proper thrash. Half way through the car seemed to transform itself and went from a snail to a rocket.

Luckily that rocket type performance (well rocket to me anyway lol) has stuck ever since but it has made me think whether the car was in limp mode. Before you all ask I have actually cleaned the MAF and yes it did make a good difference at the time. The only thing is there were no visable lights that ever come on durring these sluggish periods, so I have a few questions about limp mode:-

1) What are the symptoms of the ECU going into limp mode?

2) What method can be used to detect the fault? i.e. VAG COM, dashbord indications or any other tool etc

3) What is the best way to clear the limp mode? i.e. disconnect battery etc

So guys i would appreciate any comments of this subject and also any past experiences you have had.

 

[Austineer]

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1) What are the symptoms of the ECU going into limp mode?

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The car wont be boosting properly. it will cut the boost back to a 'safe' limit.

Rich

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Rich,

Thanx for the info mate. However I did say that the car always indicated full boost when in sluggish mode and not any type of reduction. I thought perhaps the Ignition timing might have been retarded etc to create this sluggish effect at full boost. I am honestly not sure what is happening hence the thread, but there is a massive differenece between the two different states when under the same boost.

 

[RichA3Turbo]

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1) What are the symptoms of the ECU going into limp mode?

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The car wont be boosting properly. it will cut the boost back to a 'safe' limit.

Rich

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Rich,

Thanx for the info mate. However I did say that the car always indicated full boost when in sluggish mode and not any type of reduction. I thought perhaps the Ignition timing might have been retarded etc to create this sluggish effect at full boost. I am honestly not sure what is happening hence the thread, but there is a massive differenece between the two different states when under the same boost.

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Doesnt sound like limp mode to me then. all limp mode does is drop boost right down. It could be that the MAF is knackered... Know anyone who you could swap with to try it?

Rich

 

[RichA3Turbo]

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Rich,

So you think its the MAF then eh, I was thinking along these lines also noting that I wasnt actually loosing boost. Unfortunately I dont know anyone who to swap it with for a quick trial, so may look at getting a trade in via audi.

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Not a bad idea Mat. I think its around £70. i'd be surprised if this does not cure the problems, but if not then atleast you've eliminated one possibility albeit not the cheapest.Hopefully there are no deeper lying issues.

Rich