V70 T5 -07 28.000km - Jerky Acceleration Uphill

[Skillerns]

Originally Posted by 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.

It’s hard to say if previous owners felt or even cared about these symptoms. I would think most wouldn’t care, not even notice but I’m very picky with my car and my belongings. I like to take care of them to make them last longer, so when I feel something is off, I just have to fix it.

The tuning was done to get more horsepower. It is around 260 hp originally, now it is about 325+ish.

I’ve tried to view live data on several different sensors. Haven’t gotten any bad numbers so far, the fuel trims looks normal and so does the oxygen sensors in that case.

The catalytic converter is changed from previous owners to a sport one. So it is not as environmentally friendly as it should be when cold.

The brake booster is not checked from my part. Though I did try to vacuum test the entire system without success (hoping to find a leak).

I haven’t measured the compression in the engine, I can sure try that and buy a little kit.

Volvo VIDA has been connected to the car from the workshop without any relating codes except that it reads a “faulty software” which is said to be read as soon as the ECM has been tuned.

Funny thing is, if this helps, and this was a surprise to the mechanics, they have never seen this before: The car has been in the shop two times for a quick read of fault codes. The first time was in a try to reprogram the throttle body which never worked because the car wouldn’t accept the software, they couldn’t even reset the ECM to make it work. But we ended up not trying to program the new throttle body since it didn’t make any change in the behavior of the car. The second visit was just a read of fault codes. Now to the weird problem. After both times, after they have had Volvo VIDA plugged in, as soon as a left the shop, the car went haywire. It was so weak, jerky etc, a bunch of fault message spammed in my dashboard and it made it impossible to drive the car in a good manner. I plugged in my own reader, an iCarsoft VOL 3.0 and saw a bunch of fault codes that different modules failed to communicate with each other. I erased the codes and the car worked as before again. The exact same thing happened both times and no one knows why. And this made the mechanics even more suspicious that the ECM is at fault.

What do you think?

[Skillerns]

Originally Posted by 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 .

What does TPPS stand for?

I have read live data about several sensors, throttle body angle, gas pedal position etc and hasn’t had a weird value when looking at the date at the same time the IDLE drops suddenly.

Have not tested the VVT yet, but have changed the solenoids controlling them. Both on the intake and exhaust side.

[Skillerns]

Originally Posted by 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

VIDA is not showing any fault codes more than I can see. Though I haven’t tried their live data but have tried my own. I’m gonna try to try more of that in spring or as soon as I fix a problem I have with the code reader with the seller. It works just that it crashes after a little while which is really frustrating and makes it hard to keep a long diagnosis when reading the live data.

[john.wigley]

Originally Posted by Skillerns

What does TPPS stand for?

It's shorthand for (in English) Throttle Pedal Position Sensor, 'Skillerns. I don't know what the Swedish translation is, but you probably have an equivalent abbreviation for it! Maybe Accelerator (UK) or Gas pedal (US)?

Regards, John.

[Skillerns]

Originally Posted by john.wigley

It's shorthand for (in English) Throttle Pedal Position Sensor, 'Skillerns. I don't know what the Swedish translation is, but you probably have an equivalent abbreviation for it! Maybe Accelerator (UK) or Gas pedal (US)?

Regards, John.

Ah yes, was on the right track then 😅

I’ve done a live data on the voltage on the TPPS and can’t see any abnormalities. The voltage doesn’t drop or rise when the drop in idle occurs. I even went as far as I bought a new gas pedal but returned it since it wasn’t faulty in my tests. Though I have had for a brief moment a fault code on it. It disappeared as suddenly as it appeared. It never returned again after that, and that was more than 6 month ago now.

[olliecampbell]

I'm pretty late to this party, but bleeding a clutch is just the same as brakes. Sometimes the reservoir is linked on the master cylinder, you can usually see a divide between the front and back half of the reservoir. One is brakes, the other clutch.

This is how I test manual clutches:
Handbrake on
4th gear
Slowly lift the clutch pedal until it starts biting.
Carry on lifting it and see if it slips or stalls the car.

Whenever I've had similar issues (ok not on Volvos) it's been ICV or vacuum leak related. When you did the vacuum testing did it hold a vacuum for a period of time?

I hope that helps.

[ASt85]

Check all the black silicon vacuum tubes - the rubber elbows have a habit of perishing on the inside bend yet look intact - primary ones are those that connect from the back of the air filter box.

[Skillerns]

Originally Posted by ASt85

Check all the black silicon vacuum tubes - the rubber elbows have a habit of perishing on the inside bend yet look intact - primary ones are those that connect from the back of the air filter box.

Ive done two different ways to test for leaks but none has given any results. Do you know like a blueprint for all the vacuum lines for my model? So I know exactly where to look?

[Skillerns]

Originally Posted by olliecampbell

I'm pretty late to this party, but bleeding a clutch is just the same as brakes. Sometimes the reservoir is linked on the master cylinder, you can usually see a divide between the front and back half of the reservoir. One is brakes, the other clutch.

This is how I test manual clutches:
Handbrake on
4th gear
Slowly lift the clutch pedal until it starts biting.
Carry on lifting it and see if it slips or stalls the car.

Whenever I've had similar issues (ok not on Volvos) it's been ICV or vacuum leak related. When you did the vacuum testing did it hold a vacuum for a period of time?

I hope that helps.

I’ll try that for sure, I did in first gear and that stalled the car, oh well it was snow so it started dragging the back wheels.

What does ICV stand for

[olliecampbell]

Originally Posted by Skillerns

I’ll try that for sure, I did in first gear and that stalled the car, oh well it was snow so it started dragging the back wheels.

What does ICV stand for

idle control valve. Sometimes called an idle air control valve. But having said that if your car is a diesel it won't have one...