Hesitation/stall help

[Gazdkw]

The car has had a random hesitation recently. No pattern, it will just hesitate when cruising along at say 30, it quickly recovers. It's happened 2 or 3 times over the last week.

Today it very slowly lost power and stalled. No stuttering, no drama....the engine jusy slowly and calmly slowed down and then died. I managed to pull over safely. No lights or warnings.

It would not start initially but after a minute or 2 it started. I revved the engine hard for a minute and it drive fine back home.

I have investigated the EGR and it seems fine. Not clogged up or anything. A couple of the sensors were oily so I have cleaned them out.

Any ideas?

Some info that might help.

It's had a new fuel filter around 6 months ago and oil and filter change.

The swirl flap has recently stopped working (I noticed it around 5 months ago) it's drive fine up until very recently so I doubt that's the issue.

My suspicion is that it's happening only when under light load. The few times it's happened I have flipped gear selector into manual and revved the car and its been very responsive. It's also never happened when towing the caravan (which we didn2 weeks ago)

A mechanic friend of mine said it could be one if the injectors starting to break down.

[Kev0607]

Could be an injector, but I'm more swayed towards the swirl flaps.

If the flaps are full of carbon (which is likely the reason why they stopped working in the first place), the flaps may have got stuck in the closed position. This means you have to rev the car more and may experience hesitations.

EGR and fuel filter would have been the other culprits, but they seem okay from what you describe.

Have a look on VIDA to see if there's any underlying codes. Some faults don't immediately throw an engine management light.

[Gazdkw]

Originally Posted by Kev0607

Could be an injector, but I'm more swayed towards the swirl flaps.

If the flaps are full of carbon (which is likely the reason why they stopped working in the first place), the flaps may have got stuck in the closed position. This means you have to rev the car more and may experience hesitations.

EGR and fuel filter would have been the other culprits, but they seem okay from what you describe.

Have a look on VIDA to see if there's any underlying codes. Some faults don't immediately throw an engine management light.

Would this not have shown up when the swirl flaps stopped working?

[Tannaton]

Swirl flaps would not cause an engine to stall or non-start.

I'd keep a code reader with you - non start is either low fuel pressure or no injector pulse.

Slowly losing power is most often low fuel pressure...

[Gazdkw]

Originally Posted by Tannaton

Swirl flaps would not cause an engine to stall or non-start.

I'd keep a code reader with you - non start is either low fuel pressure or no injector pulse.

Slowly losing power is most often low fuel pressure...

Yes, my local volvo specialist said the same this morning. What's the usual culprits for sudden low fuel pressure?

[FreshAir]

The Car Scanner app (paid) will do data logging so you could log the fuel pressure, which varies with load anyway, plus anything else that may be useful. Then if you can capture on an occasion when it fails you can look for different data trends compared to before it failed.

As for cause I couldn't be sure. Thinking what is needed to determine fuel pressure/injector needs - rpm, air flow at inlet, boost pressure & temperature, 'throttle' position. Or mechanically could be the filter (I know you have changed it already but I wouldn't dive too deep without changing it again).

[Kev0607]

Originally Posted by Gazdkw

Would this not have shown up when the swirl flaps stopped working?

Mine didn't. No fault codes on the dash, but VIDA revealed the underlying issue.

I misread your original post, I didn't realise that it stalled. Inoperative swirl flaps won't cause stalling, but they can cause hesitations.

The stalling is more likely fuel pressure, fuel regulator or something along those lines. Fuel filter is a good start... go for a good brand one. I know its been changed a few months back, but its a cheap part that can cause lots of problems.

There's lots of things that can cause low fuel pressure;

-Dirty fuel
-Clogged fuel filter
-Fuel pump
-Clogged fuel lines
-Injectors

[Gazdkw]

Originally Posted by Kev0607

Mine didn't. No fault codes on the dash, but VIDA revealed the underlying issue.

I misread your original post, I didn't realise that it stalled. Inoperative swirl flaps won't cause stalling, but they can cause hesitations.

The stalling is more likely fuel pressure, fuel regulator or something along those lines. Fuel filter is a good start... go for a good brand one. I know its been changed a few months back, but its a cheap part that can cause lots of problems.

There's lots of things that can cause low fuel pressure;

-Dirty fuel
-Clogged fuel filter
-Fuel pump
-Clogged fuel lines
-Injectors

If i remember rightly it was a bosch filter and it was done in May so more like 4 months ago.

I still keep coming back to the fact the car didn't start missing, stuttering before it stalled. Surely a lack of fuel pressure would show this type of Symtom?

[Kev0607]

Originally Posted by Gazdkw

If i remember rightly it was a bosch filter and it was done in May so more like 4 months ago.

I still keep coming back to the fact the car didn't start missing, stuttering before it stalled. Surely a lack of fuel pressure would show this type of Symtom?

I would have thought so. It sounds more like a blockage or a restriction. Check the filter to see what its like. Something as simple as a bad batch of fuel can cause problems. Or try putting a bottle of injector cleaner into the fuel. Dirty injectors can cause hesitations.