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Discussion Starter #1 (Edited)
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.
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Below are screenshots from the Car Scanner app:

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

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Fuel Trims at ~2000rpm

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Failed O2 Emissions Tests

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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.
 

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Hey,

Sorry to hear all the trouble the T4 is giving you. Have you checked the intake valves?
 

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Discussion Starter #3
Thanks for the reply, no I haven't, seems like it's something that might be a bit out of my technical reach.
 

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It looks like that engine computer think that put enough fuel to the engine, but by some reason, real amount of fuel is less.
Note, that there is no "fuel flow sensor" on the fuel lines. Car computer calculates fuel consumption by computing "fuel injector debit" x "total time injectors are open". So, it look like there is not enough fuel debit trough injectors(some problem with the injectors), or.... fuel pressure is low. But there is a fuel pressure sensor, so it should raise an error, if there is a problem with fuel pressure.
Of course, there can be other problems too...
 

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Dodgy battery or batteries can throw up all sorts of error codes. Gotcha post below interesting, says secondary battery can generate errant codes too.
Probably not that but worth looking for elimination.
 
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