C30 2.0L loosing power when warm
 

Hi All

My C30 seems to run fine until it gets to normal operating temperature and then it seems to loose power. It still feels "fine" until about 2500-3000rpm and then it has this weird hesitation (like you can put your foot flat on the accelerator and barely anything happens) and to make it weird it sort of comes right higher up the rev range (can't recall how high up, possibly around 4500). So it doesn't loose power completely it just sort of levels off.

Some years back I had a similar issue with a V70 and it ended up being an ignition coil so I've replaced them all so far but no luck. To make it even trickier, it doesn't always happen.

I've asked the independent dealer to have a look last time it was serviced but they said all was fine so I assume there were no codes.

Any ideas?

Thanks,
R

Generally speaking (very generally) ...

Cold: the ECU follows a fixed map for fuel & timing. Warm: the ECU will adjust the fuel & timing based on sensor readings.

My guess is that maybe a sensor reading is wrong (the sensor may be fine - the connection to the ECU may not be) resulting in AFRs being out or the timing being pulled. This won't always generate a fault code.

Getting hold of VIDA & the appropriate OBD scanner & monitoring what parameters go out of range, or if the short term fuel trim is maxed out, when this fault occurs is the best way to be sure.

Good luck & keep us informed of your progress

Thanks Paddy

Getting my hands on a Vida is gonna be a problem right now, so for a start I think I'll yank out the throttle and give it a good clean and also leave the battery disconnected while busy so as to reset the Ecu. I'll do a physical inspection of the wiring harness for anything obvious issues and clean all connectors. Then I'll warm it up and if it still does it, try disconnecting some sensors like MAF, intake temp etc (one at a time of course) to see if I can find the culprit. Will disconnecting the 02 create a permanent fault?

Thanks again,
R

Ok so ...

1. Cleaned the throttle
2. Cleaned both O2 sensors
3. Clean all engine related connectors I could get my hands on (including ECU connections)
4. Set spark plug gaps to 0.8mm (the gap was on the big side, suspect they are due for change at the next service)
5. Had battery disconnected for the whole time so presumably the ECU would have reset.

Unfortunately the "turbo lag" is still there. It's fine when cold but as soon as it reaches normal operating temp it feels like the power gets cut back. Once it gets to about 5000rpm it starts feeling normal again though, which is strange.

I'm assuming the 2.0l has no MAF as I could not spot anything resembling one.
Where would the knock sensors be located? Have read they could cause issues once they start to fail.

Thanks,
R

The first thing you must do is measure the fuel pressure whilst the problem is happening .... It may well be ok at idle but not when the pump has to work hard ...

Hi Clan

Where does one test fuel pressure on the C30? It does not have a valve on the fuel rail like the V70 I had previously.

Also, I found the fuel filter and I suppose its a good item to replace also, but what is that other canister behind the fuel tank?

Thanks,
R

we don't have external fuel filters for the petrol in UK . the other cannister is the charcoal cannister where all the fuel tank fumes collect and get drawn back into the engine as it is illegal to vent fuel fumes to the atmosphere .
Most garages should have a universal fuel pressure gauge which fits in between the fuel delivery pipe and fuel rail .

So I got a fuel filter but man those quick release clips on the fuel line are not playing the game. I even managed to somewhat mangle the one by using vice grips to try and depress the tabs in order to pull the line off but they weren't having any of it. Any ideas other than buying new fuel lines?

Also, I decided to disconnect the fuel line from the fuel rail in order to release the fuel pressure and realized that there was quite a bit of movement in that connector (it slides quite a bit in and out, not so much sideways) and it does not feel as secure as the rear connector (in that short piece of fuel line). Could this be part of my problem?

Also also, where is the fuel pressure regulator situated? I thought I found it but it turned out to be part of the evac canister system.

Thanks,
R

Finally got my hands on a cheap fuel pressure gauge and did a quick test this afternoon (need some rubber fuel lines to connect it inline for a proper test) and so far it shows 4 bar pressure. Does that sounds about right?

Any ideas on getting the clips to release on that fuel filter?

Thanks,
R

yes 3.8 bar it should be ..
But were you monitoring it at the exact moment you get the problem?