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2014 T4 Very High Fuel Trim

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Old Apr 3rd, 2020, 10:30   #1
bertusras
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Default 2014 T4 Very High Fuel Trim

Hello all,

I have been battling with my 2014 V40 CC T4 for quite some time now. The car has been to Volvo twice, and a 3rd party Volvo specialist and no-one seems to know what is going on.

My issues started with the car misfiring on cold start. From what I've read regarding Ford Fiesta ST's (which have the same engine), this is quite a common occurrence. Once the car switches to closed-loop, the misfires go away as the AF is controlled by the O2 sensor.

However, in trying to diagnose what might be causing this, I picked up that the car has ridiculously high Long Term Fuel Trims (LTFT), which has worsened over time.

I am getting the following codes on a regular basis:

P2177 - System too lean off idle, Bank 1

P0300 - Random/Multiple cylinders - misfire detected

P0301 - Cylinder 1 - misfire detected

P0303 - Cylinder 3 - misfire detected

P2681 - Engine coolant bypass valve control - open circuit

What has been done to the car:

- I did find a vacuum leak after the MAF sensor, where some technician 'rolled' the seal on one of the intake ducts leaving a gap. Thought that fixing this would have solved the issue, but it didn't.
- Cleaned the MAF sensor with the correct MAF sensor cleaner, no difference.
- Swapped sparkplug order from 1-2-3-4 to 4-3-2-1, still misfiring on 1&3. Then swapped coils the same and still misfiring 1&3.
- Volvo replaced the Fuel Pressure Sensor, no difference.
- Volvo removed and cleaned the coolant bypass valve, which stopped the P2681 error for a while, but it has come back. I have now replaced the valve with a new unit.
- 3rd Party specialist went through all the electrical connections, checked all hoses, and whilst the car was there apparently the misfire stopped. Unfortunately, I broke my hip whilst the car was there, and the car stood for 6 weeks before I was able to use it again, and the problems persisted.
- Tried looking for a vacuum leak again, but can't find anything obvious. Used both the blow smoke into the hoses and propane around connections whilst running and monitoring STFT approaches.
- Ordered a new MAF sensor, but it is stuck in customs due to lockdown.

Below are screenshots from the Car Scanner app:

Fuel Trims at Idle (LTFT is SCARY, have seen it as high as +40%)

Fuel Trims at ~2000rpm

Failed O2 Emissions Tests

I really am at wits end right now. Volvo now wants to replace the injectors, but they can't be certain that it'll fix the problem, and that's not good enough for me.

My gut feeling is still that this is a vacuum leak, as the idle fuel trims are higher than the on-throttle trims. At WOT the trims are lower, but still very, very high. But, with trims this high, it should be a MASSIVE leak and I should be able to find it fairly easily, right?

Secondary feeling is that it's faulty data from a sensor, either MAF or O2?

Am I correct in assuming that there is too much air in the system, and the computer is compensating by injecting more fuel? Could leaking gaskets have anything to do with this?

I also need to replace the battery, could it be that low voltage is causing the misfire as the injectors and not working properly? Surely this won't have any effect on the fuel trims once the car is running though?

Edit: I forgot to mention that the fuel economy has deteriorated as well (to be expected), however my issue is that the actual consumption (km driven compared to fuel put in) is wildly different to what the computer is reporting. Last couple of fill-ups give the following comparison:

Actual | Computer

11.36 | 15.6
10.37 | 14.1
10.81 | 15.0
10.97 | 15.1
9.67 | 12.9

It used to vary by about 1l/100km

I'm just about to drive this car off a cliff, so any help or tips would be greatly appreciated.

Last edited by bertusras; Apr 3rd, 2020 at 11:01.
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Old Apr 3rd, 2020, 13:42   #2
Tannaton
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I don't think you have mentioned (unless I missed it) whether the car is under warranty or not, I'm assuming not as it's been to an Indie, but if it is you should continue with Volvo.

I've had a theory for a long time that cars are so well engineered now that it is very rare for sensors, injectors etc. to fail and cause problems like this, usually it is another problem - like the one you described with an ill fitting seal.

For example, if just fixed an old Ford Ranger pickup I bought recently that's been to and from the main dealers and other garages (with the previous owner) with a random hot starting issue - thousands have been spent on it in the last 18 months. Assuming it to be a fuel pressure regulation issue (in the absence of any codes) I stripped, cleaned and re-assembled every part of the fuel system that can influence system pressure. I found a spec of plastic in the over pressure bleed valve on the fuel rail, and a few bits of muck elsewhere. I can't be certain what made the difference as I did it all in one got but it's a different vehicle now, not only is the starting issue fixed it's a smoother, more responsive vehicle. No parts where replaced, just stripped down as far as possible, cleaned and re-assembled.

And I would suggest you do the same. I don't know much about this engine specifically, 99% of my tinkering is with diesel now but the change in behavior when it switches to closed loop as it warms up is a massive clue I'm sure and that does not point to injectors.

So I would be tempted to strip, examine, clean and check the whole fuel system (if you are able to do that) and see how is goes from there?

Next step would be to start looking at the real time data during warmup and running, i.e. fuel pressure, duty cycle, O2 etc.
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Old Apr 6th, 2020, 09:00   #3
bertusras
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Thanks for the reply Tannaton.

Unfortunately the warranty expired at the end of '18 (2014 model sold in late 2013), otherwise the car would have been parked in their workshop until they figured it out.

I do also have a slight inkling that it could be something to do with the fuel delivery system, and not the air delivery system, due to the fact that the actual and computer fuel consumptions vary that greatly. It feels like the computer is trying to push more fuel, but for some reason it's not getting delivered. If it was an air leak, the correct amount of fuel would be arriving to compensate.

There's a good YouTube channel which deals with stripping down a Fiesta ST (which engine Volvo has borrowed for this car), and they have a fuel rail disassembly and cleaning segment. I'll re-watch it again, but it did seem within my technical reach when I first watched it - time was against me at that stage. However with another week and a half of full COVID lockdown, there's lots of time to get to this now.

Good idea, thanks! The more I'm able to eliminate, the better!
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Old Jul 8th, 2020, 16:29   #4
bertusras
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Okay so a ton of money and four new injectors later, the car is peachy.







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