Morning all,
I’m still chasing a misfire on my ‘cheap’ 4.2 s/c RRS I’m slowly narrowing it down:
Compression is good across all cylinders (both hot and cold)
All coil packs are good
Plugs are new
02 sensors are good

Starting to suspect it’s fuel pressure related - subject to me getting a y piece adapter to get a gauge on the rail. The pressure reading in SDD seems low, but no pressure related codes are being triggered.

however…. My diagnostic journey has identified that it;s previously been worked on by a bevy of circus clowns:
- there are lots of missing covers and brackets
- the cats have been butchered and are just empty cases
- the power flow ‘sports’exhaust is shot

I also have paperwork from 2014 for a power ‘remap’ which is the reason for my post.

I have been using SDD with some success and would like to get an original map back on the ECU but could do with a few things.

1. If someone can provide me with an unmolested map file or at least a file name/date to hunt down that would be fab
2. Or - point me in the right direction to get one-without spending out at a main dealer

Also I’ve noticed that the ECU is backed up into other modules - but in my case it ‘seems’ to be the the same file name that’s been backed up.

sorry lots of rambling - probably demonstrating my inexperience in this space.

Anyway - all advice gratefully received

Getting into maps and uploading is way beyond my pay grade.

But could you not just pick up a second hand 1 from the same car. It would probably need some programming to match your car but surely SDD would do that.

They dont seem to be high costs. You would also have something to compare with, and/or take the map yourself.

J

i had a miss fire on my xk8 which turned out to be a very small water leak dripping onto a coil pack, of cause when the engine was hot the evidence was evaporating

marjon said:

Getting into maps and uploading is way beyond my pay grade.

But could you not just pick up a second hand 1 from the same car. It would probably need some programming to match your car but surely SDD would do that.

They dont seem to be high costs. You would also have something to compare with, and/or take the map yourself.

J

Click to expand...

That may actually be an option, I was however a little nervous about changing the module as I have heard anecdotal stories of vehicle mileage being updated from instrument packs or ECU changes (paranoid me?)

badfluffy said:

i had a miss fire on my xk8 which turned out to be a very small water leak dripping onto a coil pack, of cause when the engine was hot the evidence was evaporating

Click to expand...

My XKR suffered from exactly that issue of a torrent of water leaking through the bonnet vents and getting under the coil pack covers

JokerUK said:

Morning all,
I’m still chasing a misfire on my ‘cheap’ 4.2 s/c RRS I’m slowly narrowing it down:
Compression is good across all cylinders (both hot and cold)
All coil packs are good
Plugs are new
02 sensors are good

Starting to suspect it’s fuel pressure related - subject to me getting a y piece adapter to get a gauge on the rail. The pressure reading in SDD seems low, but no pressure related codes are being triggered.

however…. My diagnostic journey has identified that it;s previously been worked on by a bevy of circus clowns:
- there are lots of missing covers and brackets
- the cats have been butchered and are just empty cases
- the power flow ‘sports’exhaust is shot

I also have paperwork from 2014 for a power ‘remap’ which is the reason for my post.

I have been using SDD with some success and would like to get an original map back on the ECU but could do with a few things.

1. If someone can provide me with an unmolested map file or at least a file name/date to hunt down that would be fab
2. Or - point me in the right direction to get one-without spending out at a main dealer

Also I’ve noticed that the ECU is backed up into other modules - but in my case it ‘seems’ to be the the same file name that’s been backed up.

sorry lots of rambling - probably demonstrating my inexperience in this space.

Anyway - all advice gratefully received

Click to expand...

Cats, they are monitored by the ecu also. So unless they've been programmed out they'll need replacing to put it back as it should be or the engine will never be happy

Interestingly I've just taken the RRS out for a run with my icarsoft in theory logging data in real-time but in actuality nothing got saved!
So I plugged SDD in and looked at the snapshot data held against the P0305: Now as soon as the misfire count hits the magic threshold the code is thrown and the car drops into restricted performance.
I'm definitely not an expert here but looking at the snapshot data it suggests that the fuel pressure was next to zero as was the manifold absolute pressure:
Which may be I suppose the effect of the restricted performance trigger given I had accelerated firmly to trigger the fault - I will try again to get a more of a sequence of data - as the snapshot appears less useful - unless fuel pressure really did drop to 0.168KPa

Trouble code (fault) that caused required freeze frame data storage 773
Fuel system status for bank 1 2
Fuel system status for bank 2 2
Calculated load value 100.0%
Engine coolant temperature 62.0°C
Short term fuel trim bank 1 -32.7%
Long term fuel trim bank 1 -28.0%
Short term fuel trim bank 2 -22.5%
Long term fuel trim bank 2 -28.0%
Fuel rail pressure - Gauge 0.4410kPa
Manifold absolute pressure sensor 0.1680kPa
Engine speed 3418.50rpm
Vehicle speed 84.0kph
Ignition timing advance for cylinder 1 -47.0°
Intake air temperature 20.0°C
Mass air flow 220.290g/s
Absolute throttle position 69.02%
Commanded secondary air status - Upstream of first catalytic converter No
Commanded secondary air status - Downstream of first catalytic converter inlet No
Commanded secondary air status - Atmosphere/off No
Time since the engine started 216
Commanded exhaust gas recirculation 0%
Exhaust gas recirculation error -28.0%
Commanded evaporative purge 0%
Fuel level input 37.6%
Barometric pressure 0.1000kPa
Control module voltage 13.9640V
Absolute load value 155.7%
Commanded equivalence ratio 0
Relative throttle position 57.65%
Ambient air temperature 11.0°C
Absolute throttle position B 75.29%
Accelerator pedal position sensor - Circuit D 47.06%
Accelerator pedal position sensor - Circuit E 45.49%
Commanded throttle actuator control 100.0%
Sensor power supply monitor 0V


I need to get some more data to see the values over time

Mark Piercy said:

Cats, they are monitored by the ecu also. So unless they've been programmed out they'll need replacing to put it back as it should be or the engine will never be happy

Click to expand...

Yes, totally agree, it is a little chicken and egg though as I don't know why the cats were removed.

- did a misfire kill the cats causing them to be smashed out as a'cheapo fix'
- were the cat's removed and programmed out when the sports exhaust was added ?

Ultimately the cats have to be re-fitted but before I go near them (spending monies) I need to make sure that there are no misfires that would kill the new cats

I have a TDV6 disco3 and have a nanocom and can use it to remap all the computers back to standrd

Is the P0305 code specific to a misfire on cylinder 5
depending on how they're numbered I think thats the bank on passenger side second from front

JimS said:

Is the P0305 code specific to a misfire on cylinder 5
depending on how they're numbered I think thats the bank on passenger side second from front

Click to expand...

So looking at the two numbering options it's either - 3rd back on the drivers side or first at the front on the passenger side
I pulled the coil and started it to work it out and it's Front left

I've swapped coils around and compression tested but all looks good from that perspective - I'm trying to avoid throwing parts at it hence the diagnosis.

Currently trying to rule out fuel pressure issues.
- The workshop manual suggests fuel pressure rail is about 3.35 bar at idle (which from the diagnosis it is reading low)
- The manual also suggests that pressure from the pump is variable but operating pressure is 5 bar (presumably max)
- ..and the manual says each fuel rail maintains a fuel pressure of around 4.5 bar (lower at idle higher at full load)

I've graphed fuel pressure against load% and it certainly increases with load - whether the average is low I'm not sure at the moment

Forgive if I'm wrong but is there a fuel regulation on both sides of the engine and is there a vacuum pipe to each? If so trace them back to there connection and check for vacuum leaks on the pipes and at the connection point?

Fuel rail has temp sensor on one side and pressure sensor on the other (with a vacuum line)

Fuel pump pressure is regulated by a fuel pump driver control module in the boot linked to the ECU fed by the pressure sensor - at least that is my schoolboy summary of what I've read
It's not clear what the vacuum line on the sensor does - I'm hoping to get a pressure test done on the rail to see if the sensor is accurate - I could also see if I can push some smoke up the vacuum line

JokerUK said:

Fuel rail has temp sensor on one side and pressure sensor on the other (with a vacuum line)

Fuel pump pressure is regulated by a fuel pump driver control module in the boot linked to the ECU fed by the pressure sensor - at least that is my schoolboy summary of what I've read
It's not clear what the vacuum line on the sensor does - I'm hoping to get a pressure test done on the rail to see if the sensor is accurate - I could also see if I can push some smoke up the vacuum line

Click to expand...

Thank you for explaining that, if your pressures are not to speck maybe a visit into the fuel tank once you've exhausted other avenues?

Mark Piercy said:

Thank you for explaining that, if your pressures are not to speck maybe a visit into the fuel tank once you've exhausted other avenues?

Click to expand...

Yes, well I had almost convinced myself I needed to drop the tank and look at the filter or pump or both - just trying to be sure

if code is for a miss fire on 5 its not fuel rail pressure or it would show miss fire on more than one cylinder

badfluffy said:

if code is for a miss fire on 5 its not fuel rail pressure or it would show miss fire on more than one cylinder

Click to expand...

A very good point, it's also the fuel pressure that's casting doubt.

badfluffy said:

if code is for a miss fire on 5 its not fuel rail pressure or it would show miss fire on more than one cylinder

Click to expand...

Yes, I know it's a misfire - I started with plugs, coil and injector all OK - I'm expanding the search to see what else can cause it

Suspect a minor vacuum leak, if you swap the coilpacks but the fault remains on 5. Smoke test a good idea.
Assuming the connectors have been examined to see if any of the crimps have been slightly pushed out (at the #5 coilpack and at the ECU end)

Thanks Jim, I purchased a smoke tester last week and of course the cone was too small for the maf inlet which resulted in an unsatisfactory bodge with a ploy bag and gaffa tape - but did get me as far as leaky throttle body seals - which are hopefully fixed. Looking for a better smoke cone adapter to continue the inlet testing.

I actually purchased a pair of coil packs so I could do some swapping with known good parts - but yielded nothing.

compression is good and consistent across all 8 cylinders

I will look at the wiring - that’s a helpful steer.

As background the Code only gets thrown under load

I am concerened though , hence the original post, that the ECU mapping is non-standard and would really like to put a standard map on as I can’t be sure what could have been mapped out.