S60 2.0T - stalling and LTFT majorly out [weak fuel pump] Topic is solved

[TroyMcClure]

I’ve never monitored STFT under heavy load but it seems logical It should spike, doesn’t it.?

That won’t cause the LTFT to bump unless you are flat out on the M1 all the time

I'd say it's logical that it'll need to chuck more fuel in, but that the map would already know this therefore the fuel trim would be close to 0. At +25 I'd say it's fairly far off where it expects to be and is having to compensate.

You're right in that unless I'm flat out all day it shouldn't affect LTFT, but it's out enough that even a few bursts of acceration will increase LTFT enough to be an issue over time.

I've been playing around with the Torque app again today and found some useful data I hadn't used before. Rather than looking at fuel trims to measure how lean it's running, I've instead looked at actual AFR.

Nearly all the time in normal driving it's close to 14.7:1 (good). At WOT however it's nearer 17:1. Not horrendously out when compared to stoich BUT it should be running rich at WOT by my understanding - something like 12:1. Even with STFT at 25%, to me that sounds like it's running in the region of 40% leaner than it should be. Can't be good for the engine.

Also interesting that the other car I tested this in (admittedly not a Volvo) goes open loop when approaching WOT. The S60 stays closed loop all the time other than when off throttle. Any significance in this?

[TroyMcClure]

Thought the parts to date had collectively resolved this to a usable point - i.e. no longer stalling... however I think a lot of "light" driving in traffic = no WOT = no chance for LTFT to spike... and stall.

Foot flat to the floor on a sliproad last week, car choked and stalled while doing 70. That's a new one. Garage seems baffled by it still.

Against original plans I'll continue to replace parts, provided none of them are overly expensive. Next up is a front O2 sensor, genuine Bosch per the MAF to rule out any cheap parts playing havoc.

Pending this, I'd be really grateful if anyone with a P2 (preferably the 2.0T) and Torque/another OBD app could plug in on their next journey and post any of the following:

- STFT under load (ideally 40mph+)
- Whether fuel system goes closed loop under load - mine remains open unless off throttle
- How quickly fuel system goes closed loop from cold. Mine was open until coolant temp was just 8c and about 50m down the road then switched over - surely that's too soon?!

Thanks to anyone still reading.

[abscate]

It can go closed loop as soon as the OXS is hot enough to GIVE reliable exhaust readings. On my P80s that took about three minutes but the P2 is faster

[TroyMcClure]

It can go closed loop as soon as the OXS is hot enough to GIVE reliable exhaust readings. On my P80s that took about three minutes but the P2 is faster

Three minutes (maybe a little less) sounds more like it. I just timed mine from the data recorded in Torque, it took 15 seconds from a 5c start before it went closed loop. Seems too soon to me, but if it's based on how soon the O2 sensor heats, it could be right.

[jonesg]

P2 sensor has its own heater coil.
15 seconds sounds quick but maybe.

[TroyMcClure]

I've fitted a new front O2 sensor as that was the next logical part to replace. It's definitely not fixed the issue, if anything the STFT values seem more extreme. After doing so I've also had a pending P2195 - O2 Sensor Signal Stuck Lean bank1 sensor1 and Torque states Closed loop, using 1 O2 sensor (feedback fault). No P0101 however.

This initially felt like progress, but from Google I'm still none the wiser which makes me wonder whether:

- The new sensor is faulty, OR
- The new sensor is more responsive than the old one, albeit the issue is still there and much like the P0101 the new code and failure mode are a failsafe and not indicative of the actual issue.

I must admit I thought the car only used 1 O2 sensor for AFR anyway, so that message is slightly confusing.

Can anybody else ascertain anything from this? Should I replace the secondary sensor too? (though thought this was for emissions only...)

As a side-query... I've built myself a DIY smoke tester to double check for vacuum leaks. Not convinced the garage spent much time looking after finding the obvious one. If I connect just after the MAF, will this test the whole system or will I need to plug it onto the PCV system separately to test that? Beyond the intake/turbo I don't know how air flows through the engine.

[abscate]

Where are you on fuel pressure checking? The P2 platform does eat a fuel pressure sensor or PEM once in a while

[TroyMcClure]

Where are you on fuel pressure checking? The P2 platform does eat a fuel pressure sensor or PEM once in a while

It's not been checked yet, though I've read pressure sensors can be the culprit. That said, mine is fine through the range unless under load, so surely it's more likely to be delivery than the sensor (or module)? Will be hard to test as the fault is only prevalent under load and can't be replicated when the car is static... Or would it still be worthwhile?

In other news, I gave my home-made smoke tester a try today. No leaks to be seen (plugged it in just after then MAF then separately into the pipe going from crank case to oil trap) so I'd like to think I've ruled out a vacuum leak. I'm not sure whether smoke testing the PCV system would indicate anything, especially if it's blocked rather than leaking. They are a servicable item on these so may still replace anyway - assuming I perservere with the car. That said, I've put a glove over the oil filler and it seems to have reasonable suction rather than inflating which I understand suggests it's ok...

I also wanted to check the plugs to see if lean running was isolated to individual cyliders. All looked ok, which is to be expected as they were only changed in September, but worryingly one of the plugs was loose and had oil up the thread. It didn't seem to go back in particularly tight so I hope the thread hasn't been stripped previously. Going to get a reverse thread chaser for next time they're out to see if that helps.

Still grateful of any and all suggestions... this mystery is driving me mad.

[DavidE7]

This sounds like it could be a plugged fuel filter or failing fuel pump in addition to the other suggestions of fuel pressure sensor or PEM. The reason I say that is because of the stall following an acceleration. You have no information about fuel supply if you are not checking the fuel pressure using a gauge on the Schraeder valve.

[TroyMcClure]

UPDATE: I'd been dealing with the issue for a couple of months by... not driving the car much and ignoring the problem. Finally got round to visiting yet another specialist earlier this week, reason being that this one had a rolling road. With the issue only manifesting itself under load, short of having someone's head under the bonnet at speed this was the only way we were going to find it.

One rolling road session later and it sounds like DavidE7 (and others that previously alluded to fuel supply issues) hit the nail on the head:

This sounds like it could be a plugged fuel filter or failing fuel pump in addition to the other suggestions of fuel pressure sensor or PEM. The reason I say that is because of the stall following an acceleration. You have no information about fuel supply if you are not checking the fuel pressure using a gauge on the Schraeder valve.

Pressure was measured at rail of around 3 bar at idle and partial load HOWEVER under heavy load it dropped by around 1.2 bar to 1.8 bar. That certainly won't be helping. Good news is that it isolates the issue to fuel delivery. Bad news is that with no codes, I was informed it would be difficult to diagnose which component was at fault (read: cheaper to replace parts than test them).

So, which part I replace first will be based on best guesses, however I'd really appreciate some help with the following to decide;

1) There is definitely no FPS on the fuel rail, nor do I get a reading for fuel pressure in the Torque app. Is it safe to say that my model doesn't one? Or is there somewhere else it might be? I can get a pic of the rail if needed.

2) The PEM is proving similarly difficult to locate. Being a late '04 (and facelift) model, I looked in the spare wheel well first, but there's nothing. Next looked on top of the tank (note it's a plastic tank,part 8671616) and can't see it there either. Youtube videos suggest only metal tanks have it there anyway. Volvo have the part number down as 30742823, so I assume it must be hiding...somewhere?

3) However... as the drop off in pressure was consistent and only under load my gut feeling (and garage said it made sense, but couldn't be 100% sure) is that the pump would be the most likely culprit. It sounds like the correct pressure is being commanded but the system physically can't keep up when asked. I would expect if it was the PEM or FPS (should it exist) I'd be seeing erratic readings at various loads - or all-out failure.

Fuel filter had already been replaced and made no difference. Even if the tank was gunked up, I expect it would've run better temporarily until the filter caught it all again.

Only other potential issue I can think of is a kinked fuel line, but again expect this would restrict across all rev ranges.

Bonus: If someone has access to VIDA and would be able to provide a diagram of the fuel for my exact model, please PM me so I can send my VIN... I'll happily donate £10 to a charity of your choice in return.

Feel like I'm getting there... hopefully, worst case scenario (though with this car I can never be sure) I have to replace the PEM and fuel pump to fix, but at this point I'd take that.