Power loss then power back again

[Minigirl]

On the way to work at 60mph in 6th I felt the car slowing to 55 like i was going up hill and it felt sort of shakey / rough (like an off balanced
Wheel) and the gear icon telling me to shift down to 5th. It still felt unresponsive and started telling me to shift to 4th. I stook with 5th for a few mins then all was normal again and it told me to shift to 6th again then it was all fine and smooth

Any ideas on what it was? Spark plugs possibly as no idea when they were done?

Thanks

[Thrumbleux]

I know you've had problems lately (now solved with Evil's sump gasket) with oil leaking, but now that's solved, how is oil consumption?

[Minigirl]

Hi, fitted the gasket 7 weeks ago and filled to half way mark on dipstick, I use the car 5 days a week so that 35 days @ 30 miles a day which is 1050 miles and the mark is still near enough at half way on the dipstick so not really using oil which is good :-)

The car is at 60 odd thousand miles, how often do the plugs need changed?

At first I thought I had a flat tyre the way it was slowing down and the sound like maybe a missfire unless a coil is on its way out

Thanks

[Thrumbleux]

Can't remember plug change mileage - it's on FQ101 and/or Eviliution IIRC.
Does sound like a misfire - except misfires will light up the EML. And tend not to sort themselves.

[mikerj]

Could be the start of the boost control valve dying. These a common failure, though more often they stick in a position that gives too much boost and the ECU switches to limp home mode with no boost at all. The part is pretty cheap (£20) though they are a fiddly PITA to get to, being mounted on the back of the TIK pipe support bracket.

[Thrumbleux]

Pushed into limp mode by overboosting from faulty boost control valve doesn't reset without battery disconnect.

[mikerj]

Yes, if overboosting it will need an ignition cycle to restore normal operation. If the valve is sticking in the other direction then boost will drop (controlled only by wastegate actuator spring) but no fault code or limp mode will occur. This is assuming OP's car has the valve fitted (i.e. 61bhp rather than 50bhp).

[Minigirl]

Thanks, noticed something this morning, when first setting off I can hear a relay click in the pass footwell and the car sort of looses power then a few seconds later it clicks again and power is back then it clicks again and power is reduced then a few seconds later clicks again and power again back to normal then its fine.

Is that normal?


Thanks

[Thrumbleux]

No, not normal.
The only clicking I hear from footwell is when the rear wiper is on.

[Minigirl]

Maybe a dodgy relay but thought it might have been some cold start relay as it only does it two or three times on start up

Hasnt done the original reported problem again since that friday morning

Thanks

[BobbaFett]

Just curious but does anyone know at what point (pressure) the cycle valve actually cuts boost? I assume this is set from the ECU and cycle valve itself is not mechanically pressure sensitive?

[Thrumbleux]

At max permitted boost - which is at 0.5, 0,8 and 1.0 bar for 37, 45 and 55kW models respectively, and yes, under ECU control for M160/1 Euro 4 engines. Earlier engines are slightly different.
ECU also opens wastegate on cold start - to coincide with aux air pump activation. Possibly the 'click' from the footwell.

[BobbaFett]

Ah, that's the noise your hear after the car comes off cold start and ticks over for a short while afterwards

[Thrumbleux]

Yep, when the wastegate is then closed, you can sometimes here the turbo start to spool up. Wastegate is held open to permit as much heat as possible to reach the cat as early as possible and thus reach 'light-off' earlier. Has the added bonus of not trying to spin up the turbo before oil has reached it. Pretty neat tricks.

[Minigirl]

Haven't had the problem since but do still get the click and power loss and click power gain relay thing on cold start first thing in the morning so maybe is the ecu controlling the wastegate on cold start


How do you tell what bhp model you have?

Thanks