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Thread: 3.2 FSI Petrol, very lumpy idle when cold problem

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  1. 3.2 FSI Petrol, very lumpy idle when cold problem 
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    Hi guys,

    Been struggling to figure out an issue with my car only when cold that suddenly started happening a few days ago. When the engine is cold, and the weather is cold, you start it up and it's really rough, relunctant to rev (if you try to rev it misses badly). So all I can do is let it idle, after a few mins it all smooths out and it drives fine.

    The colder the weather the worse it is, often stalling. You cannot set off until it's all smoothed out and idling fine.

    I suspected a faulty ignition coil pack as they are known to fail, as the spark plugs were only changed about 4K ago. However there were no faults logged at all in VCDS which was strange, everything I read suggested a misfire should be logged. Initially I was thinking to change all 6 coil packs.

    However yesterday I moved the car, same issue, and when I had finished I noticed the cooling fans were on full pelt, turned off the AC and still going.

    This evening I needed to use the car, worst ever lumpy idle, took a good 5 or so minutes before I could set off. However I noticed the coolant temperature gauge was showing just below normal operating temperature which it couldn't have been as the engine was cold and hadn't been run for over 24 hours.

    I'm pretty sure my issue here is a faulty coolant temp sender. If it is saying the engine is hot then the cold start map would presumably not cut in and the fueling would be set accordingly. That would explain the low and very lumpy idle, cooling fans cutting in and why it runs fine when warm. Would also explain why no faults logged.

    Appreciate any thoughts on this. Driving me nuts and would love to get it fixed.

    Thanks in advance for any help.

    Andy
     
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  2. Re: 3.2 FSI Petrol, very lumpy idle when cold problem 
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    Which version of VCDS are you using?
    Anthropogenic climate change, the biggest con inflicted on mankind since religion...

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  3. Re: 3.2 FSI Petrol, very lumpy idle when cold problem 
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    Hi Crasher, latest one 18.9. I have a proper VCDS not a copy so it always updates.

    Any ideas would be gratefully received.

    Thanks

    Andy
     
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  4. Re: 3.2 FSI Petrol, very lumpy idle when cold problem 
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    Sorry forgot to put version in, 18.9
     
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  5. Re: 3.2 FSI Petrol, very lumpy idle when cold problem 
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    Quick update. Pretty sure it's the sensor, I unplugged it this morning, car started fine, revs just above 1k, then settled down after a couple of mins, no misfire etc. Turned off, plugged sensor back in and restarted. Lumpy idle back. I know the part number so will be getting a new one.

    Hopefully an easy and cheap fix
     
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  6. Re: 3.2 FSI Petrol, very lumpy idle when cold problem 
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    My Octavia did this a few weeks ago. Really difficult to start but no codes, when cold the engine temp showed as 112 degrees, it was -3 outside! New Febi sensor as well, I only fitted it 12 years ago....
    Anthropogenic climate change, the biggest con inflicted on mankind since religion...

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  7. Re: 3.2 FSI Petrol, very lumpy idle when cold problem 
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    Thanks Crasher,

    Do you know what would happen if I drove with the sensor disconnected? Going to drive it to pick new one up, will it just run rich?
     
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  8. Re: 3.2 FSI Petrol, very lumpy idle when cold problem 
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    It runs at default which I think is 40 degrees. Make sure the engine is cool and you release the system pressure before you start, I ended up in casualty with severe face scalding because of one of those, stupid owner had fitted a new sensor but not fitted the clip correctly. It was Golf G60 and to do the timing you unplug the sensor with the engine hot and running, hit me under the chin and all over my face, I even had a square dent in my chin where the sensor hit me! I was going to the Frankfurt motor show the next day for the unveiling of the new Golf 5 I was covering for a magazine and I had a red blotchy face covered in ointment....
    Anthropogenic climate change, the biggest con inflicted on mankind since religion...

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  9. Re: 3.2 FSI Petrol, very lumpy idle when cold problem 
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    Quote Originally Posted by apole View Post
    Hi guys,

    Been struggling to figure out an issue with my car only when cold that suddenly started happening a few days ago. When the engine is cold, and the weather is cold, you start it up and it's really rough, relunctant to rev (if you try to rev it misses badly). So all I can do is let it idle, after a few mins it all smooths out and it drives fine.

    The colder the weather the worse it is, often stalling. You cannot set off until it's all smoothed out and idling fine.

    I suspected a faulty ignition coil pack as they are known to fail, as the spark plugs were only changed about 4K ago. However there were no faults logged at all in VCDS which was strange, everything I read suggested a misfire should be logged. Initially I was thinking to change all 6 coil packs.

    However yesterday I moved the car, same issue, and when I had finished I noticed the cooling fans were on full pelt, turned off the AC and still going.

    This evening I needed to use the car, worst ever lumpy idle, took a good 5 or so minutes before I could set off. However I noticed the coolant temperature gauge was showing just below normal operating temperature which it couldn't have been as the engine was cold and hadn't been run for over 24 hours.

    I'm pretty sure my issue here is a faulty coolant temp sender. If it is saying the engine is hot then the cold start map would presumably not cut in and the fueling would be set accordingly. That would explain the low and very lumpy idle, cooling fans cutting in and why it runs fine when warm. Would also explain why no faults logged.

    Appreciate any thoughts on this. Driving me nuts and would love to get it fixed.

    Thanks in advance for any help.

    Andy
    Where was this sensor located on your car?

    Sent from my SM-G930R4 using Tapatalk
     
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  10. Re: 3.2 FSI Petrol, very lumpy idle when cold problem 
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    Hi,

    Sorry for the slow reply, life has been hectic.
    @Crasher, ouch, that sounds painful. I changed my sensor, easy to do and did it when engine cold. Quick and easy fix. Didn't drive the car much whilst waiting for part, threw an engine management light. Once sensor changed I cleared it, just FYI it logs a code under the engine module and the HVAC. Been great ever since.

    The sensor on my engine is very easy to get to. Under the front engine cover that says V6, black plastic pipe going left to right in front of engine block, sensor on top of that.

    Thanks everyone for all the help.

    Andy
     
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