Solved 2010 V70 T6 idle surge

ALVO360

Hey people,

I'm hoping someone can help me figure out a surging idle issue I have with my V70 T6.

Idle surges when warm. You cant hear it when inside the car or really notice it on the tacho, but when your outside the car it's very audible.

When I pull the dipstick, idle clears up and becomes as smooth as silk.

Vacuum in the dipstick tube - relatively high by my standards, but no positive pressure.

PCV box replaced less than 3 months ago.

I do have a leak from the turbo. I know it's a common issue for one of the oil feel line bolts coming loose. Still yet to tighten that up due to the awkward position.

Unrelated to the idle, I've also replaced the Fuel rail pressure sensor, genuine Volvo plugs and cleaned the maf.

Any help would be appreciated.

ALVO360

I found this interesting:

https://www.matthewsvolvosite.com/forums/viewtopic.php?t=78791#p423906

I might get onto the turbo feed line just to rule it out.

My Volvo Infected brain can't figure out how the surging idle and oil feed line could be connected?

Any suggestions would be very helpful.

ALVO360

I tightened the oil feel line on the turbo and still have the same idle surge. The feed line was definitely loose and I'm glad I got onto it. Not much room to work with in there...

Graeme

Alex

It might be helpful to think about this: Check the YouTube videos on tracing manifold leaks, one I came across was a guy going through the process on a Volvo.

Usually a surging idle is the result of an air leak in the induction system

ALVO360

Thank you @Graeme

I'm suspecting the culprit is the charge pipe coming from the turbo. I'll look for vacuum leaks and report back with the outcome.

I appreciate the help - thank you!

ALVO360

I've been troubleshooting this over the weekend and could not find any vacuum leaks. I wouldn't mind replacing the charge pipe coming from the turbo, but I don't think it's the culprit.

I replaced my PCV box because I was advised to do so for an unrelated issue. Because it was a service item and I didn't know when it was last done, if at all. But thinking back, I believe the idle issues began after replacing the PCV.

Now, when I was under the hood I noticed this little vent hole on top of the round PCV valve on the box.

With the car running I put my finger over this hole and it made the classic high pitched PCV sound -

I repeatedly blocked it off with my finger and released it once the high pitched noise would become present.

After repeating this process 7-8 times the noise disappeared and the idle returned to normal...

So, my conclusion is the diaphragm inside the PCV was stuck and not functioning correctly.

My symptoms were that of a failed PCV, but I wrote it off as the likely cause because it had only just been replaced. The V70 now has a smooth idle and I'm relatively confident the issue has been resolved.

PolestarJad

ALVO360

I created a new login just so I could reply, to say thanks for posting this.

My T6 was doing exactly the same after changing the PCV. I googled, found your post, did what you did, now it seems to idle smooth again. Very weird! Haha.