# Limp mode - Help needed



## Pysle1 (Jan 19, 2016)

Hi

for about 1 year i have had this boost problem with my TT. The problem is boost related and throwing the car into limp mode(safe mode).

The symptoms are: When i start the car from cold the car runs great for about 20 minutes. boosting all the way up to 1.3 bar(18-19 psi) max. no misfires or nouchyness through the rev range. But then all of the sudden after 20 min have passed, it drop down to just maxing 0.6 bar(8-9 psi) and the car feels super slow. This happens sporadically and not happening just when i'm on max boost. it also happens when i cruise on the highway at 80-100km/h without putting any boost/pressure on the turbo(lets say i have been driving nicely and want to accelerate and then i realize: "aw, gone into limp mode again". If i turn the ignition off and on again, the problem is gone until it occurs again a bit later.

When this problem started for about 1 year ago i checked my fault codes with vag-com. on of the codes was triggered my O2 sensor. bought a new O2 sensor and fault code still occurs). after some research on forums i see people have two O2 sensor. i have just one pre-cat O2 sensor.

Specs of car and what i have upgraded/tested
Audi TT 180 AJQ Quattro 1999mod 210km

- BSR stage 2 chip with exhaust after cat and out.
- Changed out many rubber lines with silicone and fixed minor boost-leaks
- 2.0 coil packs upgrade
- Changed spark plugs (NGK) 6 months from now. (did not check the gap, can this be the problem if they are now gapped at .028mm?)
- Tested with a working n75 valve
- n249 delete
- Forge diverter valve (tested with OEM aswell)
- New O2 sensor 
- Cleaned MAF sensor.

Can this be caused by the MAP-sensor even though no fault codes are showing(not maf there are two different things)?

Any help or answers is much apreciated


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## miknix (Jul 26, 2015)

Are you sure it's limp mode? Do a Vag scan and check for faults to confirm. For a long time I thought I was losing boost, when in reality the car was just adapting the throttle to my driving. If you cruise for some time with low throttle and you never request full throttle, the car will adapt to that to reduce fuel consumption. Usually, when the car is adapted to low throttle/city driving, doing a couple of consecutive WOTs will make the car deliver full throttle again.


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## Pysle1 (Jan 19, 2016)

miknix said:


> Are you sure it's limp mode? Do a Vag scan and check for faults to confirm. For a long time I thought I was losing boost, when in reality the car was just adapting the throttle to my driving. If you cruise for some time with low throttle and you never request full throttle, the car will adapt to that to reduce fuel consumption. Usually, when the car is adapted to low throttle/city driving, doing a couple of consecutive WOTs will make the car deliver full throttle again.


I think you just led me to the solution! Yes pretty sure it goes into limp mode. Solution: i cleaned my throttlebody 1 year ago when this problem startes to occur. I remember i read on here that you could just turn on the ignition an let it sit for a couple of minutes, i remember i did that but clearly that did not work AS it should. This was before i got vag-com.

To fix the problem was just to realign the TB in vag-com.

Been driving/testing the car constant on now for 1.5 hour and it has not fallen Into limp mode. Looks like Victory.

Thank you again for gotten me out of this problem which almost made me a madman!


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