FSi Uneven idle when up to temp...???

chrisnic

chrisnic

Member
After replacing the thermostat on my FSi and finally getting a reading on the temp gauge, another issue has cropped up.....!!! The car idles fine when warming up, but once up to 90 degrees and only sometimes, the car will rev higher (1200 rpm) whilst idling...!!! If I put on the aircon or the fast windscreen demist, the revs fall back to a normal idle...!!! I have cheked and cleaned the camshaft sensor so far, so any advice on what else to check would be appreciated......

Thanks in advance....
chris
 
I only have basic scanning software (app) that only shows p1031 error and is easy enough to clear...!!! would a full scan point to the faulty component...??? I'm near sutton/croydon if anyone has vcds and can do a scan...!!!
chris
 
Hi,
That P1031 error relates to the inlet manifold flaps. They are either stuck, or not moving through the full rotation range. Depending on the position they're in, the engine management may well be struggling to get the the mixture right once the engine comes up to running temperature. You need to figure out what is happening, and a licensed version of VCDS will do that, via the potentiometer output. Once you know, what's what, you can consider the options. If the flap spring is returning them to the rest position (open) the ProBoost map may be for you. If the flaps aren't fully open with engine off, this would need fixing first, as (I'm assuming) the ProBoost map is based on flaps permantly open. @A2Steve can comment on my assumption.
Mac.
 
PlasticMac said:
Hi,
That P1031 error relates to the inlet manifold flaps. They are either stuck, or not moving through the full rotation range. Depending on the position they're in, the engine management may well be struggling to get the the mixture right once the engine comes up to running temperature. You need to figure out what is happening, and a licensed version of VCDS will do that, via the potentiometer output. Once you know, what's what, you can consider the options. If the flap spring is returning them to the rest position (open) the ProBoost map may be for you. If the flaps aren't fully open with engine off, this would need fixing first, as (I'm assuming) the ProBoost map is based on flaps permantly open. @A2Steve can comment on my assumption.
Mac.
Click to expand...

Yes Proboost map works on flaps open at all times so they would need to at least be free moving to resting position before fitting.
 
I will check to see if the flaps/actuator are actually moving - I know the connecting rod is not brocken and does move (long nose pliers) last time I checked...!!!

Odd that it was running fine before the thermostat was replaced, but I gues it was never getting up to temperature info before...!!!!
 
Have a read of the P1031 thread, especially the posts from @Andrew and @lfield. The suck test might be your next best move. Look for 15mm movement on the actuator rod. If less than 15mm, the flaps are not rotating through their full range. P1031 strongly suggest that they're not. To find out where they're starting and finishing, use VCDS or the @lfield multimeter check.
Mac.
Edit:-

@chrisnic This post explains things:

fault p1031

I did consider clamping the pipe to see if the vacuum was leaking away through the actuator or somewhere else, but couldn't get in there with Mole grips with the intake hose in place. But it does sound like it's all operating as it should even if it thinks it isn't and is bringing the MIL on...
www.a2oc.net www.a2oc.net
 
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