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B4164T Very High Fuel Trim

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6.6K views 8 replies 4 participants last post by  bertusras  
#1 · (Edited by Moderator)
Hello all,

I'm on the Fiesta ST Forums out of desperation. I have a 2014 Volvo V40 T4, which has the same 1.6T B4164T engine as the MK7 Fiesta ST's and I'm hoping someone here might have some ideas as to how I can fix my issues.

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.
 
#4 ·
Thanks Jason, no, O2 sensors are my next step after replacing the MAF (one thing at a time to try and eliminate a single culprit).

K3FUS, I also think it's a vacuum leak, but I cannot for the life of me find it. A compression test would reveal issues with the head gasket, correct?

Someone else on the Volvo forums suggested that I should disassemble and clean the entire fuel system, as it could be a fuel delivery issue due to a small blockage somewhere - thoughts?
 
#5 · (Edited by Moderator)
Thanks Jason, no, O2 sensors are my next step after replacing the MAF (one thing at a time to try and eliminate a single culprit).

K3FUS, I also think it's a vacuum leak, but I cannot for the life of me find it. A compression test would reveal issues with the head gasket, correct?

Someone else on the Volvo forums suggested that I should disassemble and clean the entire fuel system, as it could be a fuel delivery issue due to a small blockage somewhere - thoughts?
Check which Lambda sensor has the "failed heating" on it, that is a sure sign that the sensor has failed (sensor 1 is after the turbo, sensor 2 after the cat and after the first sensor - in the direction of gas flow from the engine).

Vac leaks are a pain to find, firstly start with a visual inspection of all air pipes, big and small. Then smoke test the induction system all the way to the engine and on to the smaller vac lines.

Other things to look for are:

- Fuel vent system (also uses a vacuum)

- Leaks around sensors and gaskets

- Exhaust system leaks (between the first and second lambda sensors)

- Could be a fuel starvation issue, you'd need to pressure test the fuel rail to find eliminate or confirm that one (not sure if Forscan can read that)

The high trims suggest a leak as it's adding more fuel and now running rich.

At least on this car the brake servo is fed with a mechanical pump, so that rules a leak out there.

Its a case of unplug things and block them off and see if the trims change dramatically as soon as you do something.

It took me ages to find a leaky brake servo on a car recently, but as soon as I did I knew I'd found the issue, but that was after 2 new lambda sensors and someone saying it was 100% the air flow meter!

When you check things check them twice, some times you miss read what's happening.
 
#6 ·
Thanks for that. I'll pull out the multimeter and do some checks on the upstream O2 sensor. Unfortunately I don't have one of those special lamba sockets to pull the thing out, and auto shops are closed at the moment.

My other concern is the fact that the actual versus computer fuel consumptions aren't aligned. Which is why I'm wondering if it could be a fuel delivery issue as well? If there is a leak, surely the fuel delivery should match the extra air, and the actual fuel consumption should be close?

But yeah, I think a total strip-down of the air intake and full checks are in order.
 
#7 ·
Thanks for that. I'll pull out the multimeter and do some checks on the upstream O2 sensor. Unfortunately I don't have one of those special lamba sockets to pull the thing out, and auto shops are closed at the moment.

My other concern is the fact that the actual versus computer fuel consumptions aren't aligned. Which is why I'm wondering if it could be a fuel delivery issue as well? If there is a leak, surely the fuel delivery should match the extra air, and the actual fuel consumption should be close?

But yeah, I think a total strip-down of the air intake and full checks are in order.
If you suspect a fuel supply issue reading the pressure at the rail is the first thing to do and easy with the right tool when you locate the pressure valve (like one you find on a wheel).