Revs rising/ dropping at idle

[leebes]

Hi All,

Had a strange issue on the drive to work this morning. I do about 10 miles before I have to stop at a junction, so the engine is nice and warm by then. Stopped at said junction, clutch in, foot off the power and the revs went up to approx. 1500-2000rpm and then dropped back to 800-900rpm which is standard tick over for my 07 GTi.

Wasn't sure if I imagined it the first time, but a mile down the road, hit a bit of traffic and there it was again, in neutral, the revs climbing to 2k ish and dropping to idle, then up again and so on.

Had a suspicion it could be an air leak gremlin as I removed the intake a couple of weeks back to fit a short shifter, but all seems tight and sealed there. Have just unplugged the MAF sensor, gave it a quick, careful wipe, plugged it back on and everything appears to be fixed...bizarre!

Any one had a similar issue and know if a bit of dirt or dust in the MAF could have caused it that issue?

Cheers
Lee

[Ollieeee]

I had the same issue a while back, it turned out to be the corrugated vacuum pipes off the PCV.

[leebes]

I had the same issue a while back, it turned out to be the corrugated vacuum pipes off the PCV.

Thanks, so I was on the right lines with an air leak. Will check the PCV over later and see if there's anything obvious

[lukemk5gti]

I had the same issue a while back, it turned out to be the corrugated vacuum pipes off the PCV.

This thing - http://www.ebay.ie/itm/Breather-Hose-Pipe-Line-Hose-For-Audi-A4-A6-TT-2-0TFSI-VW-Jetta-New-06F103235-/151510344696

[leebes]

I had the same issue a while back, it turned out to be the corrugated vacuum pipes off the PCV.

This thing - http://www.ebay.ie/itm/Breather-Hose-Pipe-Line-Hose-For-Audi-A4-A6-TT-2-0TFSI-VW-Jetta-New-06F103235-/151510344696

Thanks Luke 

If it is the breather hose then might be a good time to fit a PCV delete?

[lukemk5gti]

Why bother with a delete?

Do you need it? Everyone (including me) sees a modification and immediately thinks they need it. If your PCV is fine then why bother, a new hose is only €10 from China - https://www.aliexpress.com/item/For-VW-Jetta-Golf-Eos-Passat-A4-A6-S6-TT-New-Air-Breather-Vent-Hose-Line/32601636338.html?spm=2114.01010208.3.10.PYVGik&ws_ab_test=searchweb201556_0,searchweb201602_4_10057_10056_10065_10068_10055_10054_10069_10059_10058_418_10073_10017_10070_10060_10061_10052_10062_10053_10050_10051,searchweb201603_1&btsid=002a745e-81b6-4720-83b6-441aca16a85b

I would never buy a cheap Chinese rip if it for anything important but how wrong can you go with a piece of corrugated plastic pipe?

[Ollieeee]

I had the same issue a while back, it turned out to be the corrugated vacuum pipes off the PCV.

This thing - http://www.ebay.ie/itm/Breather-Hose-Pipe-Line-Hose-For-Audi-A4-A6-TT-2-0TFSI-VW-Jetta-New-06F103235-/151510344696

That's the badger! There's two though so check both, I replaced both just for peace of mind. It was cracked round the back so not immediately obvious.

[leebes]

Why bother with a delete?

Good point, well made!

[leebes]

So checked over the PCV breather pipes earlier today as suggested, couldn't see any obvious damage or leak holes so put them back on.

Thought while I was under the bonnet I'd have a clean round and make sure everything was tight, induction kit fittings, etc...and the 4 torx bolts on the PCV plate which all turned out to be slightly loose! Nipped them all up as thought there could be an air leak through the gasket.

Result - on run into town and back, no dodgy revving and the engine sounds quieter and smoother, so maybe the PCV plate has been coming loose for a while and finally loose enough yesterday to cause the leak.

Anyway, looking good at the moment...Cheers for all the advice peeps

[lukemk5gti]

Glad to see it's sorted!