Troubleshooting performance and poor MPG, D5

[Talisio]

Hi folks. Have a bit of a problem and have been going round in circles for months.

My 2008 s60 d5 (not remapped) has been performing poorly on the first start of the day (stalling on occasion) and sounding like a train at startup, the colder the weather, the worse the startup gets.

My economy also tanked, I was getting about 25-30% poorer economy, same driving habits and previously my economy had been static throughout the past few years I have owned the car.

The only way I have found to fix my economy (temporarily) is this:

When on the motorway, put my foot flat on the floor for a few seconds then let go completely.
Do this a half a dozen times and pow - my economy is back up for a few hundred miles. It dropped again today, repeated this fix and it appeared to solve it again


In the last 12 months the following work has been done

Gearbox oil changed (Geartronic auto box)
Full service
DPF checked by three seperate garages - all agreed it is fine. The car does mainly long journeys.
Two injectors replaced due to excess leak off. The two replacements have not been coded correctly - I am planning on getting this fixed but would like to know people's thoughts on my issues before doing any more work.

Thanks for your time folks

[sam1]

there are more knowledgeable people than me. but if it was me i would start here:

spray carb cleaner through the MAF
check MAF is operating within parameters
check other fuel system related components to see within spec - manifold pressure, coolant temp, fuel rail pressure etc. look at what could **** it up.
fuel filter replacement
strong mix of injector cleaner over a tank of motorway driving.

other considerations - wheel alignment, tyre pressures, good quality tyres.

i used to average about 36 mpg from my 2007 v70 auto 163hp with mixed driving.

re cold start - glow plugs and or glow plug controller need checking - in my experience glow plugs do fail, which makes cold starts sound bad and run rough for first minute or so

[37 RUBY]

Hello Talisio

How have the garages confirmed the DPF to be good? Via diagnostics?

You don't mention whether or not the car fault codes have been read.

If it has and there are none, the MAF is one such item that doesn't tend to log fault codes.
You could unplug the MAF and force the computer to use a predetermined set of values. If you get an improvement it could indicate the MAF or associated wiring as an issue.

If it hasn't been read for codes it should be the next port of call.

[5cilinder]

Dpfś are accumulating ash wich cant be burned that gives extra backpressure
And that geartronic gearbox is parasitic drag , also tire lining and pressure is important

[Talisio]

Originally Posted by 37 RUBY

Hello Talisio

How have the garages confirmed the DPF to be good? Via diagnostics?

You don't mention whether or not the car fault codes have been read.

If it has and there are none, the MAF is one such item that doesn't tend to log fault codes.
You could unplug the MAF and force the computer to use a predetermined set of values. If you get an improvement it could indicate the MAF or associated wiring as an issue.

If it hasn't been read for codes it should be the next port of call.

Thank you for all the replies I will write back properly tomorrow when I finish work.
I unplugged the MAF sensor previously and the car stalled on startup. Even when I tried to rev it died and refused to rev.
Dies that just complicate things or help?

[sam1]

just re reading this... how are you measuring your 'economy' you mention range to empty, but this is a guesstimate by the ecu. i have found the average mpg computer to read +/- 3 mpg either way.

are you measuring your MPG over a full tank, and calculating it manually at the pump based on resetting your odometer before filling the previous tank? ie, zero odometer, fill tank to brim, drive until tank empty, refill tank, note amount of fuel and look at odo then put details into this https://www.torquecars.com/tools/uk-mpg-calculator.php

to see what ACTUAL mpg you are getting...

[37 RUBY]

Originally Posted by Talisio

Thank you for all the replies I will write back properly tomorrow when I finish work.
I unplugged the MAF sensor previously and the car stalled on startup. Even when I tried to rev it died and refused to rev.
Dies that just complicate things or help?

Whilst that is still not definitive in identifying your problem it does mean you definitely need to read your codes.

When you unplug a MAF a set of base parameter fuel settings are used but still rely on other sensors to compensate by providing data that allows those parameters to be utilised.

So in this case it could suggest that one of more sensors and/or wiring have faults.

Have you got an error message on the dash?

Is the throttle body clear of soot build up and allows full movement of the butterfly?

Does the egr valve in the throttle body look clear and feel free to move?

What was the % of soot in your DPF when confirmed good by the garage?

When are you going to get the injectors coded? Surely no more diagnostics can be performed until these are correctly coded.

Are the swirl flaps connected and working?

When was the fuel filter last changed? If recently, are you happy no air is entering?

For the cold start, have the glowplugs and supply voltage been tested?

So many variables when fault finding on these wonderful but complex vehicles that I'm going to have to revert to and repeat my own base set of parameters....get the codes read, preferably with VIDA but by someone who can decipher them.

[37 RUBY]

Any joy with you trouble Talisio ?