Hi Fuel Consumption on Manual D-Cat

[Mulf]

I have recently bought a manual 2009 Rav4 D-CAT with 136k on the clock, but it has several issues that I wondered whether anyone could advise me about.

The main issue is the very poor fuel economy. My old 2006 petrol Rav4 with 186k on the clock generally returned about 32mpg. The new one for the same weekly journeys is giving me about 29mpg. Both are according to the onboard computer.

Now, please don’t laugh, but we have discovered a fuel leak in the filler tube, but I’m assuming the OBC measures the fuel being pumped into the engine rather than estimating how much fuel is left in the tank?

There is also an intermittent lack of acceleration, that the chap at my local garage has said is the turbo boost coming in late. This chap, who I generally trust, says that he checked all the normal causes but wondered if the chip had been "remapped or something". He also mentioned that possibly the ECU was not working properly. He did not feel it was anything to worry about at this time.

I did see similar posts in the past where people had suggested a long run at over 2500 revs to force a DPF regen cycle. I did that and noticed white smoke intermittently at first. The smoke would be there for maybe a minute, then seem to stop, then say 10 min later would do it again. Then for the last 20 minutes, there was no white smoke. Is that normal for a  DPF regen cycle?

I also wondered whether a Tunit unit would overcome some of the problems and improve economy? If the ECU has a fault or has been remapped in the past, would a Tunit effectively override that?

 

Many thanks to anyone taking the time to reply.

 

[philip42h]

That sounds like an SR180 ... ? Mine returned an average 37 mpg (over around 60k miles).

I wouldn't trust the OBC readout - the only way to get an accurate economy figure is to use brim-to-brim calculations.

I'm not laughing, the rusted filler tube is a more or less standard feature - an unfortunate piece of design. The plastic cover that protects the filler pipe from stones etc. also traps muck and moisture and ... 

And then things get more complicated ...

When the DPF starts to get 'clogged' the system is supposed to initiate a regen cycle - once the engine is up to temperature and running at over 2000 rpm. It should complete within around 30 minutes - so, half an hour or more down the motorway is ideal. If your journey profile regularly includes such journeys you should rarely notice the regen process; if you do many short journeys the car won't get the opportunity to complete the regen and will generally be 'unhappy'.

The high fuel consumption and white smoke suggests that the car could be stuck in a regen cycle - but this is only one possible explanation, and it doesn't explain the hesitancy.

Back in the day when I had mine it was generally accepted that it wasn't possible to remap the system - so, hopefully, no one has tried. I'd suggest trying to find the cause of the issue before attempting to mask the problem with a tuning chip or whatever.

But there are loads of posts referring to this sort of problem with an ageing D-CAT and no definitive answers that I have seen.

Good luck!

[Mulf]

Thank you Philip42h

I have read that the OBC is not always accurate, but I assumed similar inaccuracies in my old petrol version. Admittedly some of my opinion of high mpg is based on the fuel I needed to buy and that could obviously have been down the leak. Ironically it was trying to do a brim-to-brim calculation that gave us an obvious puddle of diesel. Waiting for a replacement part for that and when it is fixed I'll get accurate measurements.  Luckily the part is much cheaper than the equivalent was on my old petrol version, which also rusted out about 2 years ago.