Lambda sensor fault?
 

Got a bit of a weird one with my 2002 wrx, its done it twice now, after a spirited drive the management light comes on, goes into limp mode then cuts out, if left to cool down for a couple of mins all is fine again!

The first time it did it I opened the bonnet and the turbo was glowing bright orange so would indicate overfuelling?
I can only assume that the turbo would have been a similar colour/heat today when it happened.

I plugged into it and got trouble code P1544 which points to lambda sensor. Is it reasonable to assume that a faulty lambda could cause the above fault/s? Just want to be sure before I pay £110 for a new one!

Only mods on the car are: Fully decatted + magnex catback and a blitz dump valve.

Any help really appreciated!
Thanks
Martin

Blimey. The exhaust housing shouldn't get remotely that hot on a standard(ish) WRX. Overfuelling alone shouldn't cause it - unless it's overfuelling grossly enough to be chucking enormous quantities of unburnt mixture down the exhaust manifold.

Your Blitz dumpvalve is probably causing some lift-off overfuel but it's difficult to imagine enough of it to cause the turbo to get that hot.

I'd suggest that you need to have the car looked at to find out what's causing that level of turbo/manifold heating. Given what you're saying the lambda error could be caused simply by the sensor overheating.

If you want to try a process of elimination, get rid of the dumpvalve and put the standard one back on. As above though what you're reporting sounds way out of the normal envelope - I'd be wanting to know exactly what was going on.

Thanks for the reply. Am I right in thinking that if it were overfuelling that badly that it would be popping and banging alot on overrun> Because it doesn't seem to. When it did it the other day it was left to warm up, driven hard for about 3 miles tops and the turbo was glowing after that short trip!

Can a failing lambda/O2 sensor cause any other issues with a EJ20 engine, apart from a drop in MPG?

When you say it's got a full decat, does that mean you've removed the one in the up-pipe too or just done the turbo back? If there's still one in the up-pipe it'll be concentrating the heat and muffling any backfiring. At least until it disintegrates and retreats into your turbo's (very)hotside.

Something sounds very wrong here. Have you owned this car from new? Wondering whether someone's deleted the water cooling or something else equally bizarre. As above, having someone actually look at the car would be a good move.

There are the knock-on consequences of overfuelling - possible bore-wash being the main one. On standard management the lambda sensor doesn't actually do anything once the engine's on boost so the main downside's the poor fuel economy.

Adding fuel (over fuelling) is used to cool the exhaust gas temperatures, it won't increase them! Water cooling of the centre core won't affect turbine housing temperature! (If this were a brain surgery forum I'm sure some of these people would still comment!)

P1544 is manufacturer specific, I have it down as "High exhaust temperature detected" not an Oxygen sensor fault at all......

I would suspect you have a misfire under load, plugs/coils first perhaps?

Simon

At no point did I say that fuel was being deliberately added Simon. EGT will increase if enough of it is going down the exhaust manifold and burning there. Not that that should be happening on a standard car but the evidence says otherwise.

Yes it does. Watercooling the CH reduces the temperature of the exhaust housing too - there's a surprisingly good thermal joint between the rear housing and the cartridge. Not that I can see any obvious reason why someone would want to take the watercooling off the turbo.

Really? Could've sworn you just said that excess fuel going down the tailpipe would reduce exhaust gas temp, not increase it.

Thanks for the replies. With regards to the cat question I have a straight through 3" downpipe so there are no cats left in the exhaust system atall.
When you say get it looked at, what should we be looking at? Fuelling? timing? etc?
Cheers
Martin

While risking sounding like a broken record, what replacement up-pipe have you fitted? Your comment above is a bit of a non-sequitur.

All of the above. Put it in front of someone who knows and all of that will get looked at. Something bl**dy funny is going on as a standard WRX map shouldn't do what you're describing. Timing shouldn't be an issue given it's programmed by the ECU and won't "go wrong" under normal circumstances.

Talking of which, are you sure it's still running a standard ECU, and do you have a boost gauge fitted?

This is the up pipe that I fitted:
SUBARU IMPREZA WRX STi DE CAT DOWNPIPE EXHAUST DECAT on eBay (end time 06-Apr-10 20:56:09 BST)

The car is definitely still running a standard ecu and I do not have a boost guage fitted so no way of telling what it's boosting at!

As I'm sure you can tell I'm new to imprezas but do the ecu's require a reset after any alterations as my uncles skyline required resets as it had a 'self learn' intergrated with the ecu.

That's not an "up-pipe" it's a down-pipe. You appear to think they're one and the same thing, but they're not. The up-pipe goes before the turbo and the standard one has a cat in it. As such, even assuming you have that downpipe and a catless centre section, you still have one cat in your system - immediately in front of the turbo.

These cars are unable to self learn beyond a certain point and newage cars are known to be prone to overboost when decatted, so that's another in the range of potential explanations. The best thing you can do is get the car to someone who knows what they're looking at and can diagnose it effectively and quickly.

my freind has a simular problem with a beetle. he has poor mpg, over fuelling and the exhaust glows red if he tries to use it.
he has tried all sorts including a new exhaust, new plugs, leads and a temp sensor.
he now suspects lambda sensor.

most likely cam timing

really JGM? what does he need to do to fix that? is it ecu related (mal function).
its a mexican efi version.

sorry for thread hijack

check cambelt is on correct..

JGM...i think you are correct! spoke to him at work today and the bloke who looked at it this weekend said the same. he is putting a timing strobe on it wednesday. suspect broken tooth, slipped etc

odds on passenger side pulleys are 1/2 a tooth out whoever fitted the last cam belt was happy to do this as they move when you release the tensioner . its easy to stop just gently clamp pulleys with rubber jawed mole grips then release tensioner . mine was like this when bought it missed under load and never ran right . a ex subaru wrc engineer i met at a rr day listened to the car running and told me what was wrong , got home remover covers and he was right fitted new belt as above ( didnt have proper pulley clamp) and has been spot on ever since hope this helps

Uk300
 

I have same code p1544 and p1301 when engine light comes on it won't let me rev car but if I keep trying to rev it clear,s and I can rev up and drive again last time it did it and it cleared up I drove car for 80 miles without problem to next time I started and same problem again :-( I replaced sensor only 2000 miles ago any ideas plz