V70 T5 -07 28.000km - Jerky Acceleration Uphill

[mcfe]

Get an OBD reader and look at the fuel trims.

[Skillerns]

Originally Posted by mcfe

Get an OBD reader and look at the fuel trims.

I have a pretty decent reader, so I’ve done that but nothing out of the ordinary. Does they take away possible leakage?

[TLPower]

From the symptoms you describe this is nothing at all to do with your clutch. If the clutch was slipping the revs would rise significantly without any increase in forward motion. Just to clarify the manual uses the same reservoir for the clutch as the brakes, the reservoir has a sectioned off partition for the clutch. The clutch has no bearing on how the engine idles.

My money would be on a bad MAF sensor, I see that you've changed it but it's not unusual for new ones to be faulty certainly if it's a spurious make.

[Skillerns]

Originally Posted by TLPower

From the symptoms you describe this is nothing at all to do with your clutch. If the clutch was slipping the revs would rise significantly without any increase in forward motion. Just to clarify the manual uses the same reservoir for the clutch as the brakes, the reservoir has a sectioned off partition for the clutch. The clutch has no bearing on how the engine idles.

My money would be on a bad MAF sensor, I see that you've changed it but it's not unusual for new ones to be faulty certainly if it's a spurious make.

Unfortunately the symptoms was exactly the same before I changed the MAF, and the one I changed to was a new OEM from Bosch. Still same.

I was at the mechanic today again to see if they had any new ideas. After all that I’ve already done they said the most likely reason is the ECM. That the tuning software that is used has gone bad or was bad from the very start, and my ECM is atm not able to be reset from their workshop even if they use the correct Vida software that Volvo uses, the car won’t accept the software used for a reset

Which sort of sounds likely since nothing else seems to fit. And the ECM is acting really weird as soon as you start to try something with it.

[mcfe]

I guess we just need more information. It is true that a slipping clutch would rev higher, but I am guessing there is a point where it's not that bad but also not that good.

However yeah the idle problem also suggests some other things. He's replaced most of the things that could cause it.

Resetting the ECM will just reset adaptive values which can easily be done with the battery disconnected for a few minutes. Beyond that if the car was tuned such as to increase horsepower, we can't say what the tuner did. But if it ran fine for months with a tune I can't imagine it being the problem. And to reset the ECM to factory settings it would need to be reflashed.

There are 3 more things I can think of, that need to be tested for before suspecting the ECM has gone bad.

Exhaust backpressure from a clogged catalytic converter. This should manifest as the inability to rev very high , again if not that bad it could potentially cause this in my opinion. But imagine him coming to a dead stop with the turbo spooled up, he goes neutral and all that built up pressure is pushing back causing the car to not be able to maintain 750 rpm idle speed.
Uphill would be a battle of the car trying to rev higher but can't from the backpressure.

Boost pressure sensor aka MAP sensor, I didn't see this being replaced or tested during acceleration what it's values are. Maybe there is boost loss, but I would imagine there would be some codes.

Faulty Oxygen sensor, if the fuel mixture isn't right it could cause jerkyness as more fuel or less is injected in the engine.

A quick stop at an intersection involves pressing on the brakes. The brake booster needs vacuum to operate. The seals on the booster can fail. Another thing is the check valve of the brake booster.
Some volvos were also equipped with a vacuum pump for the brake booster. Perhaps the hoses there could also be checked?

Has the compression of the engine been measured? It's fairly easy to do.

[stuart bowes]

I'm not disagreeing with anyone on any points just wanted to add this all sounds like a whole lot of guessing and not a lot of plugging it into VIDA and graphing out sensor readings which would be a lot more productive

Sometimes it really is better just to give it to a specialist and ask them to diagnose, or if you do it yourself get hold of the right diagnostic equipment, the amount of money thrown at it so far you could have done that easily a few times by now

Not being argumentative just pointing it out

[mcfe]

And I am not disagreeing with you. I am just a guy on a forum giving suggestions.

However he said he's been to the specialist and mechanic and they are just as stumped. And I can only give suggestions as to what to check for.

Only the user can test with VIDA.

[VOLVOBOY]

OP.
The MAF Sensor , the Throttle Body and the Throttle Pedal Position Sensor are inter-linked .
Have any or all been re-calibrated ? Have you checked the TPPS ? This could be faulty .
Have you checked the engine timing ? The VVT Valve is known to become sticky from gungy oil . You can easily remove this , put 12V across it and check that the pintle moves freely. It will just cost a new gasket .
Have you re-newed the Fuel Filter ?
When you put the pedal to the metal what were the conditions, ie full throttle +low revs or full throttle + high revs ? It does make a difference . High demand on the fuel pump could suggest an issue there .

[VOLVOBOY]

Ignore the last bit . You have changed the Fuel Pump and Filter .

[VOLVOBOY]

Have you got the correct length Spark Plugs ? Should be the Longer Thread .