I own a 2001 WRX, 29,000 miles and standard apart from Prodrive (WRS) backbox. This is my first ever Subaru. My car is suffering from the above problems, lumpy idle and jerky acceleration, rather like badly set up fuel injection on a motorbike, or badly balanced twin carbs. I've been for a full service at a well know independant and several trips to a local dealer, neither have made any difference to the fault. The last visit to the dealer involved changing the coil packs. The dealer has hooked the car up to the Subaru 'Game Boy' and announced all is well. I beg to differ, is it just me, are all Imperza like this or do I have a fault? The fault is now really beginning to annoy and tarnish Subaru ownership for me.
It dosen't feel all that fast either!

Hoping that someone can help.

Many thanks,

Gary.

 

I'd try to find someonewhere with some real diagnostic kit (DeltaDash springs to mind ) to check your fuelling - sounds like that's the problem to me. But the question then is what is making the fuelling wrong? Idle depends on MAF, lambda & stepper motor; acceleration depends largely on the MAF, so in my mind it points at a faulty MAF - not common, AFAIK, in the post-classics, but still quite possible. The Subaru GameBoy will not pick up a faulty MAF, only a fully broken one - not very helpful!
Thinking about it, the very early MY01s had, I think, the same MAFs as the late classics, which are the ones very likely to go wrong...
Things you could try are first resetting the ECU (likely to make the idling even worse!) then disconnect the MAF sensor - if the idle improves at this point, it's likely the MAF is mis-reading & should be replaced. If this makes no difference, plug the MAF back in again & try disconnecting the lambda sensor (the one just after the turbo, I think) and see if that makes any difference. If it does, then it could be a dodgy lambda (less likely in this case, I think!).
Erm, and go from there

 

Sounds like MAF to me!
Change it, they cost about 80quid, but if not fixed can cost a heck of a lot more!!!!!!!!!

 

get the SENSOR_ not the entire unit it'll save you a packet!

 

Part no for the MAF is 22794AA010 And there's only two small bolts hold it on, simple to do, you can get them Cheam Motors on 0208 3942263.
I got one last week, and had it the day after I ordered it, top service!!

 

Thanks for all the replies, as the cars is still under warranty I'll find out if the dealer will replace the MAF at their expense.
But I expect they'll not be willing to replace parts unless they are broken. How can I prove to them that the MAF may be faulty, and why didn't any of the mechanics at the garage mention this, they are supposed to be the experts?

Cheers,

Gary.

 

If they purely rely on their GameBoy, they won't know any better. They need to read the voltage the MAF is producing and compare it to expected results/lambda voltages. The Subaru 'GameBoy' system can't do this.
It's quite amazing that they don't pay more attention to this, as if it is the MAF which is on its way out, the next step is the engine exploding. This might cost them a little more to fix...
If you try the above ideas, and unplugging the MAF does the job (so it's defintely the MAF which is wrong), then I'd suggest showing them the bad idling & persuading them to put in a new MAF & the idling problem disappear. That might convince them! It's not as if it's their cost anyway...

 

The part number you've quoted is for the MY99 & MY00 MAF sensor RON. The MY01< cars use a different one, and AFAIAA it's not available separate from the airbox moulding at this point in time and is thus rather expensive.

As the car is still under warranty though, Gary shouldn't be paying for a replacement off his own bat.

 

Thanks lots. Spoke to the garage and they have agreed to change the MAF sensor when it is in having the clutch changed under warranty, (Clutch judder when cold). Thing is that's not happening untill Jan 14th. I need to use the car over Christmas for several long trips, in-laws in Cumbria, parents in Somerset! Am I in danger of 'breaking' my new car?
I'm worried now!

 

Just keep out of high-boost situations - on cruise it should be fine!
The ECU is fairly intelligent & should drop boost to protect the engine if there's any real problem, but basically drive the car nicely & you should be OK