Help required please!!!

[marcher2011]

Hi guys, I'm new to this site so want to thank everyone in advance for any advice or help given.

I have an 2004 Audi A3 2.0 Fsi petrol, currently my ESP light is on (the skid triangle warning light) and only that light, i have no other warning lights and the car has also had a code check and theres no codes saved at all, while the engine is running there is a very bad misfire, not quite enough to cut the engine but it trys to cut out and its very wavey when idling but also only at idle when you rev the engine it doesn't seem to jump or feel anything at all, i've search for an air leak to no avail and also checked all the valves and switched connected to the vacuum system but still the light is on and the engine is running poorly, also the brake servo no longer has air compression as the brake pedal is very hard, I did do a servo test by gently pressing the brake down while starting the car and there was slight movement in the pedal which apparently suggests the servo itself is fine but i'm now scratching my head, i'm already baulding and this is just making it worse lol, i'm hoping someone can advise me some how as to where to look now.

Again thank you guys for any help you can give me this is driving me crazy.

[Drive Blind]

who did the code check and what tool did they use?

I find it hard to believe you have warning lights on and misfires yet a code scan comes back with nothing.

You got a local VW group specialist or somebody with vcds ?

[marcher2011]

I took the car to halfords, they did the code reading. Came back with nothing, and confirmed with me that it was just the esp light that was on but they couldnt give me any info what was wrong.

[Drive Blind]

i suggest you find a local VW group specialist

or maybe try a local forum or facebook group for VW group cars, some kind person with vcds might scan it for a few beer tokens.

[Dr G]

Old 2.0 FSI was a bit of a bar steward for faults like that back in the day and they were often air/vacuum related.

You can disconnect the MAF (airflow meter) as an easy test. If it's unplugged it goes into a "safe" map rather than relying on what may well be false data from a failed meter.

Before setting fire to the car or throwing money at parts you don't need do you live nearish to any decent VAG independent?

[marcher2011]

thank you both, i shall look on facebook and forums now and i shall also look around for a VAG independant, I shall let you know how it goes.

[marcher2011]

Thank you for your advice, there are 3 codes coming up which are:
p1914- pressure sensor for brake boost (g294): implausible signal.
p0069- Manifold absolute pressure (MAP) sensor/barometric pressure (BARO) sensor correlation
p0113- Intake Air Temp. Sensor (G42): Signal too High

To me this is potentially wiring as it's 3 sensors but I'd love some input from you guys to maybe point me in a more localised direction?

[SS2.]

Can you clear the fault codes and see which one(s) come back ?

[marcher2011]

the guy asked but i said no at the time so i could get advice first, i'll ask him to clear them as he did say to let him know if i wanted them cleared.

[Smurfsarepeopletoo]

Might be worth just checking the abs ring on the hub, could be that is damaged and that would be causing the light.

[marcher2011]

I did check the sensors and the rings around the wheels but everything looked good and secure, and because of the rough running of the engine as well as the hard brake pedal thats whats lead me down the route of air leak or air related sensor. I'm now just waiting for the guy to get back to me with a time to remove the codes.

[marcher2011]

Ok so the guy was able to clear the codes for me and the esp light stayed on and didn't go out even for a second, also the engine has very slightly improved on idle but i am talking very slightly, the p1914 code did come back on which is the boost pressure sensor with implausible signal as the fault, i'm looking for a new sensor but im constantly getting MAP sensor, from what ive experienced thats the sensor going into the intake manifold, 1. are the boost sensor and MAP sensor the same? and 2. would the boost sensor be the cause of the esp light, rough idle and also the servo not having any air pressure, the last one i'm sure the answer is yes but i'd rather ask a stupid question and be told yes than to question myself and not get as much info as possible.

[SS2.]

MAP sensor = Manifold Absolute Pressure sensor.

The P1914 error seems to refer to the Brake Boost Pressure sensor.

These are not the same devices.

Whilst a defective MAP sensor could result in rough running, I'm wondering whether the P1914 error has caused the ECU to put the engine into 'limp mode'.

Apologies if I missed it but, when the error codes were reset, what is pointing you back to the MAP sensor ?

[marcher2011]

Sorry I don't think I explained the map sensor problem correctly, the only fault code I'm now getting is the p1914 which is the boost pressure sensor, when looking up a new boost sensor I get MAP sensor and boost sensor together, they even look the same and even have the same switch connection, that's why I was asking if they were the same or if there is a difference as I'm struggling to decifer between boost sensor and MAP sensor when trying to order a new one, limp mode seems somewhat right the only trouble I have with that is the engine is only running rough on idle and revs up really well under acceleration, like I said I just keep scratching my head with this one lol

[SS2.]

P1914 = Brake Boost Pressure sensor ( link)

[marcher2011]

Hi guys, i've now been in contact with Audi themselves and they believe the it is crankcase related, again either a leak or some kind of blockage, i'm going to have a good look tomorrow morning but just wondered if you guys have had problems with your own crankcase, maybe i could narrow my search somewhat?

[SS2.]

I thought the only error being returned was the the brake pressure / boost sensor.

On what did Audi base their suspicions of a crankcase (or breather) leak / blockage ?

[marcher2011]

The theory is that the code came up because there's no air passing through that sensor, they believe that the sensor isn't the fundamental problem, which makes sense as there doesn't seem to be air getting to the sensor, I just need to find where it's either blocked or leaking.