prodrive.greeny

iTrader: (3)

Alright guys,

If my dash shows code 23 does it definately mean the MAF is dead/dying (or associated wiring is damaged)? It's on my W reg turbo 2000 btw.

I need more of an experienced opinion before i commit to splashing my hard earned cash towards a new one

Thanks

NB. I have searched but can't find a definitive answer

TonyBurns

iTrader: (3)

You have an MY00 turbo, code 23 is the maf sensor, if its the original one then its had a good life, cost you just over a ton from a dealer for a new one, well worth it or the other option is a new engine at around 3000 quid, you choose which one you prefer

Tony

Splitpin

If you've got the error code then either your sensor's totally screwed, or the wiring's duff, or the plug's come unplugged. Likeliest of those is that the sensor's totally screwed (although you should clearly check the plug).

If it's any comfort seeing the CEL is the least worst way for them to fail - as long as it hasn't been dying for months before your ECU noticed. As above just over £100 from your friendly local stealer, a little less from somewhere like AS Performance or Import Car Parts. Part number is 22794AA010.

prodrive.greeny

iTrader: (3)

Thanks. I had to connect the two black cables under the steering wheel cowel to bring up the error code. Hopefully i've not done any damage to the engine as i've been driving it since i bought it with the slight hesitation on boost :s

shamone

iTrader: (1)

Could be worth an ask on the wanted section.... i managed to source a 2nd hand one for £35 thats been spot on for 25k so far!

prodrive.greeny

iTrader: (3)

Yeh i think thats the route im going to have to take - just worried a 2nd hand MAF might be second hand for a reason, ie bust??

TonyBurns

iTrader: (3)

For the cost its not worth getting a second hand maf sensor, these are cheap enough as it is new, so buy new

Tony

ZEN Performance

You will have that error stored any time the ignition is turned on with the MAF disconnected. But as above, if it doesn't have a green dot/stripe near the top hold of the sensor unit (just the sensor, not the entire housing) then it's an OLD sensor and you should just replace it as a matter of course as a service item. Don't ever buy a used one, there are plenty about and they tend to be dead!

prodrive.greeny

iTrader: (3)

Yeh this one has a small green painted stripe on the sensor. So guess it's a new one. My dealer quoted £170 for a new one. WTF!!??

ZEN Performance

The green stripe means its not older that about 5-6years, so it's not "new"!

prodrive.greeny

iTrader: (3)

Just spoke to AS Performance (thanks splitpin), and they quoted me the part no. 22794AA010 for £90 delivered so i went for it. Sould be here tomo. Really hope it works!!

Will I have to do an ECU reset after I fit it??

Thanks

ZEN Performance

You don't *need* to do a reset as the ECU will sort itself out pretty quickly, but a reset would better.

Splitpin

Ah, that's a teeny bit different. I wrote my original response on the assumption that you'd seen the check engine light while the car was actually being driven - have you seen this at all?

If not, as has already been said, the code you've seen reported via the read memory connectors is a historic one - something that has happened at some point in the past between now and the last time the ECU was reset (or the battery disconnected for more than a couple of minutes).

However, code 23 will only trigger if the MAF voltage drops out while the engine is running. Switching on the ignition with the sensor unplugged is not enough to cause the error by itself.

As such, unless you or a previous owner/mechanic has deliberately disconnected the MAF while the engine was on, replacing it still looks the best move. As above you'd be far better off running the black plug + green plug reset routine after replacing it. It'll clear off any learned corrections and will also run an active error check before it gives you the all-clear.

Also, as your current sensor is the green stripe sort, when you take it out (or use a mirror) have a look at the four digit code that should be printed in white ink on the lower part of the mounting flange. The first number's the year of manufacture (i.e. 5= 2005 etc), giving you a more accurate idea how old it is (and therefore how long it's been in there).

ZEN Performance

If you crank it with the maf disconnected it comes up as I remember, it's a common one to see after a service.

nick172sport

iTrader: (6)

hi so how do you find out if your mafs fooked on a bugeye no error codes no management light

Splitpin

The MAF sensor error check sequence only executes when engine speed is between 400 and 4499rpm. Normal crank speed is around 200-250rpm so in practice the engine needs to be rotating under its own power before the checker will run.

The fact that it stops running above 4500 also presents the risk that a sensor drop-out at high engine speeds (when you most need it to be accurate) will go completely undetected. Not Subaru's best decision that.

Splitpin

It's a problem on a classic too as in most cases they degrade/fail in a manner that doesn't cause a CEL.

The only way to test for certain whether it's reading properly is to test it off the car on a flowbench - blowing a known quantity of air past it and seeing whether the sensor generates the appropriate output.

That's obviously impractical for most people so in practice often the only way to rule in (or out) the airflow meter if your car's suffering a problem is to fit a new one, reset the ECU and see if the problem goes away. If you have access to some datalogging kit you can often spot one going, but you need to know what to look for.

nick172sport

iTrader: (6)

cheers split pin trying to iradicate problems ie removing forge dump valve to original maf as i think its running lean due to turbo not pulling much no spool up seems to work better with warm weather gonna replace maf dv boost selonoid my mates just bougjht a bug and it blew two engines before he bought it running it like normal gets a mapper in who tells him the mafs fooked no error codes no managment lights

prodrive.greeny

iTrader: (3)

Wow, very informative replies!!

I have never seen the 'Engine Check' light flash up on the dash before, only when you plug the two black connectors together.

I did actually unplug the MAF whilst the engine was running as i read on here the engine should change rpm when you unplug it so maybe thats whats caused the error code to pop up when i plug the two black cables together. I never checked the error codes before i unplugged the MAf, doh!!

I guess all i can do is wait until the new MAF shows up and fit it (and do ECU reset), and pray it fixes the problems else that'll be another 100 quid down the shoot.

Will report back tomo.

Splitpin

Oh, that would explain a thing or two. Ironically I was going to ask whether you'd done anything like that. Seeing as we know you have, that would explain your trouble code - although as you're aware yourself it's possible that there was already a historic instance of it in the ECUs memory, there's no way to tell now. The thing you've read on here is complete b*ll*cks by the way, you can't learn anything useful from unplugging the MAF with the engine running, and you also run a small risk of damaging an otherwise good sensor by doing so.

Doh indeed - but not worth worrying about now.

It's not £100 down the shoot, because the worst case scenario is that it'll give you some confidence that there's nothing wrong with the original sensor and thus the cause of whatever problem you're dealing with is elsewhere. That in itself has a value - albeit not as much as actually fixing the problem.

If nothing changes at all after fitting the new sensor and resetting the ECU, immediately take the new sensor out, back in its box and swap the old one back in. You won't be able to get a refund on the new one but it will be handy to have on your shelf the next time you start scratching your head over the old one.

Have you got the standard induction tract/airbox on, by the way?

prodrive.greeny

iTrader: (3)

Yes Splitpin, it has standard airbox.

Right then, update.

Got the sensor, fitted it all ok. There were 2 seperate codes on the old and new sensor:

The new one had: C36-700R92 and 9728
The old one i couldn't work out the whole code on it as it had eroded, but i got the second 4 digit code - 6520

Anyway, after the ECU reset i went for a light drive and then pulled over to reconnect the 2 black diagnostic cables. Turned the ignition on, and the 'Engine Check' light flashed constantly so i guess that means there are no fault codes reported??

Then unplugged the black cables and took it for a proper drive creeping right up through the rev range and surprise surprise, the engine coughed/spluttered/hesitated through boost - exactly as before, ****!

So obviously i'm back where i started, 100 quid out of pocket

Now my suspicions have swung in the direction on the BOV. It's a Bailey DV10 (was fitted by previous owner), i had it refurbished thinking a sticking spring was causing the problems noted so it's now functioning as it should. Next question is then has anyone on here had the same symptoms with a BOV fitted??

HELPPP

Splitpin

The code on the old sensor that had rubbed off would have been the same C36... number as on the new one. So the old sensor was made in 2006. Haven't worked out yet whether the remaining three numbers correspond with a date or just a batch number, but the year's a definite. If it's any comfort, it's a candidate for replacement purely on a precautionary basis given the amount of time it's likely been in the car.

Correct. Constant on/off flash = no faults stored. On this basis it sounds quite likely that disconnecting the sensor with the engine running was the cause of that historic fault.

As above, it's cost you a bit but it has taken you further through the diagnostic process. You could, as above, refit the old sensor, but we know it's getting on a bit, so if I were you, in the absence of being able to test or monitor its performance properly, I'd probably leave the new one in.

Yeah, try a standard DV and see where you get. Aftermarket dumpvalves on these don't do anything good and can cause all sorts of problems.

While you're at it, as the thread's developed you've kinda drip-fed info that it would have been handy to know at the beginning. Giving us a brief rundown of the car's specification/mods, and what you've looked at prior to starting the thread might help us help you. A bit more detailed description of the problem would probably be a good idea too. Does it start to pull fine, and then feel like it's missing, or...?

prodrive.greeny

iTrader: (3)

Thanks again.

It's a W reg Turbo 2000, it's definately been remapped but unsure by whom exactly but the former owner said it has the prodrive ECU fitted, it has the small elbow silicone hose running from turbo to intercooler but seems a standard intercooler?? .. along with the wheels and Alcon calipers. Remap wise it definately does feel like the turbo boost has been played with as the turbo does kick in quite aggresively (compared to my friends bugeye). It's also got some kind of large bore exhaust (pretty sure 3") from the downpipe back (2nd cat has been removed).

RE the hesitation issue: It varies from time to time - sometime bad, sometimes almost un-noticable but it's always there. The revs will build smoothly but as the turbo kicks in the boost feels a bit snappy. When it does it badly, the car feels like it's choked but only for a split second, then again and again through the power band. Really hard to describe but feels similar to a car whose engine mount has gone when your powering through the gears. Am i making any sense??

Splitpin

From the above it sounds like you have a PPP (Prodrive Performance Pack) or maybe even a full WR Sport car. Has it got a high level, Prodrive logo'd boot spoiler too? The PPP isn't a remap as such - it's a different ECU. If you pull the metal plate under the front passenger carpet you will probably see a pink and silver sticker. Standard ECUs for that era car would be brown or (probably) green stickers.

When it's "bad", does this feel like a sudden, very jerky power loss, a bit like a huge invisible hand has grabbed the car and tugged it backwards before letting it go again?

In as much as things like this are notoriously difficult to describe (see also: noises), yes.

ZEN Performance

If you crank with the plugs out you will very possible exceed 400rpm, as I have reset ECUs after doing just that and seen plenty of MAF sensor errors over the years.

It's easy to test a MAF sensor if you are running a standard car, and it doesn't require a flow bench. This is the first step of any remap, and just requires that the car is generally otherwise okay and the Lambda sensor is functional. Simply reset the ecu and restart the engine when up to temperature. A good maf will generally result in a closed loop fuel correction within +/- 5% and generally be centered around zero. Failing or failed maf will often be out of that range, in often sit at -10-15% (so reading rich at idle) but soon result in leaner running on load.

Simple answer is get it to someone that can datalog the car and more often or not they can diagnose it either way in 15 minutes for a small charge. In this case it might have saved £100 for a cost of £20.

Current problem sounds like it could be fuel cut, but a lean misfire could also account for it.

nick172sport

iTrader: (6)

what sort offplaces uses datalogs mot testers or rolling road specialists for my bugeye

prodrive.greeny

iTrader: (3)

What causes this bud? Excuse my ignorance but i'm new to the 'turbo' scene.

Splitpin, yes it does feel almost like an invisible hand holding the car back for a split second then releasing. Does it sometime as soon as you change up a gear during hard driving.

I've attached a pic of the car, and as you can see - no high level spoiler. I do have a Prodrive performance pack certificate in the service history but the chassis number on it has been tipexed out and mine has been written over the top. I called Prodrive with my chassis number and they confirmed they had no history of it. So I assume at some stage the car has been 'unofficially' fitted with the parts.

prodrive.greeny

iTrader: (3)

Ok, so just went out to check the ECU and it's a pink and silver label one.

On the label it says STi SP, with a few serial codes:
1001056110
A-18-000 DIX
0418

Splitpin

Yes, Paul and I are talking about the same thing. Fuel cut feels like the "invisible hand". It's caused by the boost pressure being generated exceeding the programmed target and a safety cutoff value in the ECU for more than a fraction of a second. As it says on the tin, fuel supply is then almost completely switched off to reduce the boost pressure and make sure the engine doesn't lunch itself.

There are a few causes but more of that in a sec.

That's a 99-00 PPP ECU. Tidy looking car too.

Right, so now we know what you've got, we know why your say your car feels like the boost has been tweaked - it is running more than a standard one would. As you say, the tippex on the PPP certificate and Prodrive's lack of knowledge sounds like the car has had the bits retrofitted.

As far as your possible misfire/overboost is concerned, one common way to cause it on a PPP car is to fit a decat exhaust, so if you're not 100% sure what's standard and what isn't, try to get some pics of the downpipe and centre section and we should be able to tell you.

It's also possible to get overboost if the boost control pipes are clogged with oil, or if a previous owner has tried to fiddle with the boost pressure by fitting a non-standard air restrictor.

If you are still getting the "problem" on the brand new MAF sensor then it shouldn't be a lean misfire, but that equally doesn't mean it's impossible - a weak fuel pump, for example, is a potential cause.

Does the car have a boost gauge fitted? If it does that'll tell you straight away whether it's overboost or not. In the meantime, have a look at the exhaust and see if the standard catted downpipe is still present. We'll go from there. If in doubt, you've always got the option of having it looked at by a tidy local Subaru specialist or mapper.

prodrive.greeny

iTrader: (3)

Thanks again splitpin.

It's got the standard downpipe (with cat) from the turbo and then straight through from there to the backbox which has a pretty sizeable outlet/tailpipe.

I'm guessing in regards to the air restrictor you mean the boost control solenoid? I've searched (and carried out) the 'how to clean solenoid' thread by shooting carb cleaner in it with the green diagnostic cables connected.