C70 Rumble and Occasional Lack of Power

[yomchi86]

Hello all, so I've trawled through all the C70 threads I think could relate to my issue, here's the skinny.

Bought a completely stock 2006 C70 T5 (Manual SE Lux) with a 'flutter' on idle. Price was right and I fancied a project so I bought it. I'm somewhat handy with a spanner and it's not my daily runner so I'm not too concerned if it takes a little time to diagnose. Cambelt was replaced in 2019 at 90k miles. It's now done 100k miles. Belt doesn't appear to be shiny/cracked/damaged (to my limited knowledge).

• EML - not on. (Flashes 3 times sometimes ignition Pos 2, sometimes flashes 8 times but never stays on when engine is running, nor does it light up when engine is running).
  
• Idle is rough, feels like the car is misfiring, rev counter stays constant though. Car vibrates on the flat, up and down hill with no noticable difference between the 3 angles.
  
• Car seems to smell like it's running rich. Top down and you can smell fuel.
  
• Car seems to struggle with power intermittantly. Sometimes it flies, othertimes it seems to struggle to gain speed (on flat and going up hill). Feels like there's no boost.
  
• Poor fuel economy - as in 140 miles on about 60% tank of fuel (granted with some heavy right foot action) but seems pretty poor to me?

What have I done? And with what effect?

• Spark plugs changed (old ones looked fine, genuine volvo plugs before and after) - No noticable effect
  
• Ignition coils changed (old ones appeared fine but I didn't test them) - No noticable effect.
  
• MAF sensor cleaned - No noticable effect.
  
• Battery tested and charged with CTEK 7.0. No effect, battery rated 'Good' (680/720CCA)
  
• Exhaust and Intake VVT Solenoids changed, both changed as a matter of good practice and for ease of record keeping. - Slight performance increase when accellarating but still felt like car was struggling.
  
• x2 Camshaft sensors replaced (not tested, exhaust sensor did have a fault code from what I remember on Vida) - Car flew upon replacement - I had power!!
  
• Full service (oil, filters, Throttle Control Valve cleaned - it was gunked up) - Car still flies - Hurrah!
  
• Engine top mount (the one by the coolant reservoir) had clearly seen better days (judging by the foamy brown sludge that had sprayed out and leaked on the mount. So that's been replaced - No noticable effect on rough idle.
  
• Pipe that leads to intercooler bone dry, no oil sludge I can see.

Driving today car felt sluggish again and there was a smell of fuel
I intend to get it on Vida again tomorrow and see what codes pop up. As a quick test, I pulled the MAF sensor plug out, treated it like an old Sega Megadrive game cartridge (blew on the plug and the connector) before plugging back in. Took the car out for a quick drive and again the car flew as if nothing was wrong. I've just ordered a new MAF sensor (ya know, throw some more parts at it, if nothing else at least I know they are new and less-likely to be the problem (hey, I know new parts can fail too!).

The above issues happen when it's warm or cold it seems. Anyone got any ideas? Think I'm way off in my diagnosis or thought process (I'm not too proud to be told I'm an idiot).

Car is great, when it drives properly it feels fantastic.

[yomchi86]

All faults erased - car taken out for a quick 6 mile drive. Pic attached is the output of Vida when I returned home. Again, no EML on the dash. Car still shaking on idle. There was performance today - but as I've got nothing to measure this car against in terms of 'This T5 feels the same as this other T5' I'm unsure if there are 2 issues here:

1) the DTC code about the TCV
2) the bottom mount I've not replaced yet (but have it on order)

Or if the symptoms I am facing are part of a single issue.

[yomchi86]

New MAF arrived yesterday - plugged in and took car out on 3 separate occasions. Power issue 'seems' to have gone, there's boost now but I still think the car is running slower than expected with it's power delivery.

Engine vibration is still present. Seems to get worse when the engine is warm if that makes any sense?

[iainmd]

Has it ever had the fuel pressure regulator changed? Common failure on T5s and was a recall in the Nordic region.

[yomchi86]

Originally Posted by iainmd

Has it ever had the fuel pressure regulator changed? Common failure on T5s and was a recall in the Nordic region.

Hi Iainmd - thanks very much for your helpful reply. That's a very good question, I cannot find anything in the history that would suggest that it;s been changed. I'll check the forum/google and see if I can figure out some guidance on checking this as well as potentially changing it.

I'm guessing the symptoms would be the same as what I've been experiencing? Anything that's a clear cut 'if you have 'x', then it's fuel pressure regulator'?

Cheers!

[yomchi86]

Good news, a very good friend of mine today kindly installed the engine vibration dampner that lives on the back side of the engine. The car no longer shakes. Not surprising really when you look at the state of the mount when it was taken out. So this combined with the other mount would certainly explain why the car was doing the 'Lolvo Shake'

I also checked out the sensor below the VVT solenoids - if this could be a cause of the inconsistent power...

[yomchi86]

Following the replacement of the Turbo Control Valve this morning, the above error code has now gone (following x2 separate drives out over different speeds and loads). The car now has turbo where you would expect it, in all gears and throughout the rev range. Remains to be seen what effect this has on the fuel economy but certainly for the moment I have a car that has power.

With the top down, in 4th gear and foot on the gas, you can hear the turbo too, which I've never heard before. The turbo control valve that was taken out appeared to perhaps have a leak, as there was a raised area around one of the pipes.