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

[TroyMcClure]

Evening all,

I've recently ended a c12 year ownership of Japanese cars and moved into a fairly tidy S60 2.0T.

It's off to a rough start with a cutting out/stalling issue. In summary:

- Started off fine, other than the occasional flatspot during WOT
- Idle started becoming a little erratic, but wouldn't stall until switched off. When restarting, engine fires for a couple of seconds before cutting out completely
- Scanned with Torque app, codes (sometimes live, somtimes pending) have been P0101 (Mass of Volume Air Flow Circuit Range/Performance Problem) and sometimes a P2188 (System Too Rich at Idle bank 1) to go with it
- If I clear codes, car starts again and the cycle repeats after about 15-20 miles
- During this time, LTFT slowly climbs from 0 to around 8 or 9. When it gets to this point, when I restart it will stall
- Just before it last stalled, I turned the car off with LTFT of 6.something. When I turned it back on, it was showing -23.4! Predictably it then choked and stalled when I tried to start it. See screenshot.





I was reluctant to start throwing parts at it so took the car in to a local specialist. They've plugged into VIDA but suggested other than the MAF reading a little low, everything looks ok. They've suggested it may be the throttle body, apparently the internals (not the butterfly valve) can cause these symptoms. I'm not convinced as throttle readings in Torque appear ok, plus I'm not sure it would cause the steady rise or sometimes erratic LTFT readings.

Their suggestion is to let the problem develop but I can't really run a car that needs a DTC reset every other time I want to start it! Before I start replacing parts (MAF or throttle body) does anyone have any suggestions based on the figures recorded from Torque? My knowledge is limited so I may be missing something obvious - all I can ascertain is that something is causing it to (usually) run lean and think it needs more fuel to the point of overfuelling and stalling - or in the case of the screenshot above, majorly underfuel and stall.

Thanks in advance.

[TroyMcClure]

Sorry - messed up the images in original post:

[TisMe]

I can't tell you much about the Torque readouts, but here's a couple things from diagnosing my own stalling.

If you think there's any merit to the throttle body nod, you likely don't need a new one. You can detach it from your manifold and clean it out with a wire brush/cloth and some TB/carb cleaner. Your car is a turbo, right? Then the TB is likely underneath the intake manifold, instead of to the side. A little awkward to get to, but it's literally just 4 bolts, an intake tube, and 1 electric plug holding it to your car. Disconnect all of these things and you can pull her out and clean her up. They very rarely fail mechanically, but simply suffer from carbon buildup.

You'll likely have to make out with your manifold for a while to get the TB out of a turbo, but all in all it's a simple enough job. Takes 2-3 hours if you struggle with reinserting it like I did. 1 hour if all goes super smooth.

Before doing that, I'd get a can of MAF cleaner and pull that MF out of your air filter. You don't need to remove it from the tube, just disconnect it from the airbox and spray it down. Make sure it's 100% dry before cranking it back over, 5-10 minutes will do.

One or perhaps both of these things combined can definitely improve, if not correct stalling and idle fluctuations. I wasn't so lucky, but my TB wasn't very dirty. Both of these steps did improve my hunting idle however.

Beyond that, your P2188 (System Too Rich at Idle bank 1) insinuates something as simple as your upstream O2 sensor has burnt out and needs replacing. If you start throwing money at parts, I'd start with getting a replacement Bosch. $60-80. If your car is like mine, forget about the sensor tool and just use a 17mm (or maybe 21mm) crescent wrench to loosen the sensor. Upstream (bank 1) and downstream (bank 2) sensors are different, so make sure to get the right one

Also some people say you should replace your sensors in tandem, so consider getting the downstream sensor at the same time. Not necessarily important but it could have some impact on your car's readouts.

[jonesg]

its probably a diesel.

[TroyMcClure]

I can't tell you much about the Torque readouts, but here's a couple things from diagnosing my own stalling.

If you think there's any merit to the throttle body nod, you likely don't need a new one. You can detach it from your manifold and clean it out with a wire brush/cloth and some TB/carb cleaner. Your car is a turbo, right? Then the TB is likely underneath the intake manifold, instead of to the side. A little awkward to get to, but it's literally just 4 bolts, an intake tube, and 1 electric plug holding it to your car. Disconnect all of these things and you can pull her out and clean her up. They very rarely fail mechanically, but simply suffer from carbon buildup.

You'll likely have to make out with your manifold for a while to get the TB out of a turbo, but all in all it's a simple enough job. Takes 2-3 hours if you struggle with reinserting it like I did. 1 hour if all goes super smooth.

Before doing that, I'd get a can of MAF cleaner and pull that MF out of your air filter. You don't need to remove it from the tube, just disconnect it from the airbox and spray it down. Make sure it's 100% dry before cranking it back over, 5-10 minutes will do.

One or perhaps both of these things combined can definitely improve, if not correct stalling and idle fluctuations. I wasn't so lucky, but my TB wasn't very dirty. Both of these steps did improve my hunting idle however.

Beyond that, your P2188 (System Too Rich at Idle bank 1) insinuates something as simple as your upstream O2 sensor has burnt out and needs replacing. If you start throwing money at parts, I'd start with getting a replacement Bosch. $60-80. If your car is like mine, forget about the sensor tool and just use a 17mm (or maybe 21mm) crescent wrench to loosen the sensor. Upstream (bank 1) and downstream (bank 2) sensors are different, so make sure to get the right one

Also some people say you should replace your sensors in tandem, so consider getting the downstream sensor at the same time. Not necessarily important but it could have some impact on your car's readouts.

TisMe - very sorry I hadn't noticed this first time around. Very helpful response, and you'll see from the below that cleaning the throttle body is likely where I'm going. Before replacing MAF it was cleaned, but any type of MAF issue has now been ruled out. O2 sensors check out ok, but they can go on the list of things to work through if throttle body (and potentially PCV system) not at fault.

To confirm, since my original post I've done the following:

- There was a broken hose from crank case to oil trap that had completely disintegrated. Now replaced, but made no difference, however needed doing in any case.

- Took car to be smoke tested (or more accurately, undergo a "stage 1 diagnosis") by a local diagnostic specialist. Also plugged into VIDA at the same time. Split hose found and repaired downstream of MAF, no leaks found after this. Was hopeful this would resolve, but sadly usual symptoms were back within 15 miles.

- Went back to same specialist plugged the MAF into an oscilliscope. Readings were confirmed to be slightly low so replaced with a new Bosch unit today. Unfortunately another false dawn, still no improvement to symptoms. Purge valve system also checked but seemed to be ok.

The next logical step will be throttle body or PCV. Hopefully a clean will do the trick but I'm not hopeful. Failing that, I'll likely replace both this and the PCV but looking at £300 plus before any labour with no guarantee of a fix.

I'll report back once the throttle body has been cleaned (too cold and rainy right now!) but any other ideas would be gratefully received in the meantime.

[TroyMcClure]

its probably a diesel.

This one's a 2.0T petrol.

[abscate]

If the fuel trims are still way off you have a vacuum leak and need to track that down. Mechanics love to throw MAFS at every running problem, don’t they?

[TisMe]

I think if your PCV was affecting your fuel trim, you'd have other telltale signs of issues IE; subtle oil leak and/or wispy vapor escaping in odd areas. Do a simple glove test if you suspect PCV- pull off your oil cap, use a rubber band to lasso a latex glove around the port, then crank over the engine and rev it.

A) Inflated glove = back pressure = clogged oil passage(s) and immediate maintenance required.

B) Soft and flaccid glove = PCV A-OK

I don't suspect this is your culprit but the glove test is simple and swift enough it's worth doing in your driveway, because whether it's your culprit or not, it's worth knowing the system is good. And if I owned your car, knowing that 1 PCV hose was brittle enough to poof, would be enough for me to check the system and quite possibly overhaul it.

There are PCV hoses slightly deeper under the manifold, from whence the cracked hose you found conjoins to the oil trap, that would be subject to even higher degrees of heat degradation.

I'm kind of surprised your mechanic didn't throw an O2 sensor at your car while refreshing the MAF, that would eliminate another fairly probable culprit.

Returning to the smoke test is a sincere parts-free priority.

--

Does anyone know if the Throttle Control Valve (TCV) would affect fuel trim?

[TroyMcClure]

Some time off work over Christmas and a break from other projects mean I've had chance to look at this again. Being intermittent and having the easy short-term fix of resetting LTFT through Torque means I've ignored this a bit, but with some longer trips coming up I need to get on top of it...

Interestingly it hasn't stalled for quite some time or thrown any error codes. It's either as a result of the work to date OR a couple of longer journies with minimal WOT have helped average out the LTFT so that it doesn't spike them every time I do put my foot down.

The issue is still there in some form however, as STFT still shoots up to 25 under load without fail. Idle and part load seem to be ok for now.

I took the throttle body off today and gave it a good clean. Internals look fine, I did just spray the contacts with electrical cleaner too just in case.

Sadly no luck, but it a) rules something else out and b) will hopefully extend the life of the body.

If the fuel trims are still way off you have a vacuum leak and need to track that down. Mechanics love to throw MAFS at every running problem, don’t they?

They do, and unfortunately I caved... At least it rules it out and I'm no longer having "slightly low" readings. Some further research does however suggest a vacuum leak would be more prevalent at idle. STFT is now usually ok unless under load, so if a vacuum leak with big enough to have an effect at WOT, my idle would be all over the place too?

I think if your PCV was affecting your fuel trim, you'd have other telltale signs of issues IE; subtle oil leak and/or wispy vapor escaping in odd areas. Do a simple glove test if you suspect PCV- pull off your oil cap, use a rubber band to lasso a latex glove around the port, then crank over the engine and rev it.

A) Inflated glove = back pressure = clogged oil passage(s) and immediate maintenance required.

B) Soft and flaccid glove = PCV A-OK

I don't suspect this is your culprit but the glove test is simple and swift enough it's worth doing in your driveway, because whether it's your culprit or not, it's worth knowing the system is good. And if I owned your car, knowing that 1 PCV hose was brittle enough to poof, would be enough for me to check the system and quite possibly overhaul it.

There are PCV hoses slightly deeper under the manifold, from whence the cracked hose you found conjoins to the oil trap, that would be subject to even higher degrees of heat degradation.

I'm kind of surprised your mechanic didn't throw an O2 sensor at your car while refreshing the MAF, that would eliminate another fairly probable culprit.

Returning to the smoke test is a sincere parts-free priority.

--

Does anyone know if the Throttle Control Valve (TCV) would affect fuel trim?

Thanks, there's some detailed advice here. I've glove tested the system and the glove does not inflate, with light suction pulling it into the filler slightly instead. I'm not experiencing any of the other symptoms so I don't think it's that. However, overhauling the system has been on my list of things to do as from what I understand anything on the original system over 100k miles is pushing my luck... I couldn't see any visible damage to the other pipes, but it doesn't mean there isn't any.

We've not yet thrown an O2 sensor at it, but it's been mentioned. At £70 for a Bosch one, pending another smoke test it will be something else to rule out.

I'm still waiting for said smoke test at this point, hopefully they can fit me in early in the new year. Unless I've misunderstood however, as mentioned above the good idle would suggest this isn't the current issue.

So, in summary:

- Idle and part load seemingly ok, but STFT still spikes under load/at WOT (i.e. running lean on throttle)
- Work to date is service inc plugs & filters, new breather hose, 1x vacuum leak fixed, new MAF and a cleaned out throttle body

Any other suggestions gratefully received pending another smoke test and potentially an O2 sensor.

[abscate]

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