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Ok, I've done some searching and found that I still have some questions for those who have been there before me. My SP over the last couple of weeks has developed the dreaded 'idle dip' disease - when I pull up at the lights the idle will drop almost to the point of stalling (a couple of times it has actually stalled) then pick up again to normal speed, then drop again etc. I have also noticed an increase in fuel consumption, more black sooty exhaust than usual and a particular dislike for the aircon on hot days (it has a real flat spot at low revs with the aircon running in hot weather). Despite this it performs as normal otherwise, so I don't believe it is plugs, leads, (plugs and leads are only 12 months old) coilpack or fuel filter. My research so far indicates the 02 sensor might be the culprit. My question is this - is there any advantage in fitting a wideband 02 sensor given I have a stock SP ECU? How hard is it to change on the SP - it doesn't look like a thing of joy to get to with a spanner. Have any of my fellow SP owners been down this road? Anything else I should check? your help is as always much appreciated.

Well you seem to of ruled out any other cause for it. How old is the current O2 sensor in it? As for fitting a wideband sensor, I did on my NA when it was turbo, but simply so that the wolf ecu could pick up an actualy a/r ratio

It's the original one - car has just turned 160000km this weekend, which would appear to be the lifespan of the average sensor.

WOW!!! 160k kms! That's great. Count your blessings and hopefully it's just the sensor.

My SP has done just 97k kms, and it's currently getting an engine rebuilt for the 2nd time. Not happy Jan.

Mazda supposedly replaced a bend conrod (or two) during a similar engine rebuilt while still under warranty (less than 10k kms ago). But it seems they didn't do a good job. Needless to say, I have a lot of negative feedback to Mazda's customer service and servicing in general at the moment and probably changed my opinion of their products. (Breathe deep... OK now, that I've got that out of my chest)

So I've decided to take the advise of people in the know and once and for all, fix the achilles heel of the SP - Mazda Conrods. I'm replacing the conrods with much stronger units - Carillo H-Beam Rods, along with Arias forged pistons (suited for turbo cars).

Fingers crossed, this will sort the issues.

Sorry BD, cant help you on this one. When my O2 sensor died Mazda replaced it for me under warranty. It lookes like a bitch of a job to do. Good luck.

BTW, mine died long before 100k km and it didn't help the idle droop.

Hammer wrote:So I've decided to take the advise of people in the know and once and for all, fix the achilles heel of the SP - Mazda Conrods. I'm replacing the conrods with much stronger units - Carillo H-Beam Rods, along with Arias forged pistons (suited for turbo cars).

Nice! What something like those worth? If you don't mind me asking. I'd love to go down that path.

Group buy?

Bigdawggyy

Your car is showing classic symptoms a dead bypass valve, swap yours over with "Daves" and see if it improves.

Bosch guys should have a valve on hand should be $50-60

I'm on valve 6 currently Always keep a spare in the boot now.

Increased consumption comes from afm measuring more air than is getting into the donk, hence more fuel gets chucked in.

If it does turn out to be the O2 sensor (unlikely) be prepared for a wallet raping

SPy

bigdog wrote: My question is this - is there any advantage in fitting a wideband 02 sensor given I have a stock SP ECU?

No advantage. the ECU won't make use of a wideband sensor.
It's usefull only if you have a air/fuel ratio gauge, and have a means of playing around with the mixtures
So could be an idea if you ever plan to go down that road.

Ok... time for an update. On the weekend I performed an oil change, and removed the inlet pipe from the front of the throttle body, opened the butterfly and gave it a squirt of throttlebody cleaner. Idle is now normal and car feels fine Soooo, I shall see how it is at the end of the week before I pass any judgements, but I can't really believe that one brief squirt of cleaner could make that much difference. SPy - I assume you are referring to the BOV? I might change that just in case. Pretty sure Dave has some demon tweaked BOV on his car for when he wants to run 22psi etc so I might just get a std type And thanks Rotary - that confirms what I thought was the case. Given the position of the 02 sensor i would prefer to leave it alone until I need to do a clutch or some other major surgery, then I can pull the motor and get to it easily.

bigdog wrote:SPy - I assume you are referring to the BOV? I might change that just in case. Pretty sure Dave has some demon tweaked BOV on his car for when he wants to run 22psi etc so I might just get a std type

His should fit without problem. I didnt even think about the leaking BOV

Fuzzlet wrote:

bigdog wrote:SPy - I assume you are referring to the BOV? I might change that just in case. Pretty sure Dave has some demon tweaked BOV on his car for when he wants to run 22psi etc so I might just get a std type

His should fit without problem. I didnt even think about the leaking BOV

Yep, I'm referring to the BOV, also check that the exhaust isn't leaking anywhere near the turbo too.

bigdog wrote:SPy - I assume you are referring to the BOV? I might change that just in case. Pretty sure Dave has some demon tweaked BOV on his car for when he wants to run 22psi etc so I might just get a std type

Nothing spec about my car's BOV... same one it has always had. I have never had to touch this part of the car - does that make me speshul??
As for 22PSI, I will leave that to BJ (and maybe Hammer once the new bits go in? )

Are you still running the factory BOV and plumbing (ie its still a plumb-back)? If so then it leaking shouldnt cause this issue, as its meant to vent back to the intake betweek the turbo and AFM. A leaking vent to atmo BOV can cause this sort of problem though...

yep - still stock plumback for me and Dave (I stand corrected Dave). The car is now running beautifully, so I can only assume I've cured it with the throttlebody cleaner. Best value pressure pack can I've used in a while!

how did the intake look?
if it was really dirty it may have just been a stuck IAC valve, which when cleaned has come good.
The subarus are notorious for gunking up the intake and it is part of a regular service (25K km i think) to clean up the intake.