bluenosewrx

iTrader: (2)

my dealer has told me that the emission engine light that keeps coming on is due to the sensitivity of the ECU ,and that the misfires in 2 3 and 4 that are showing on the data reader are wrong. he is currently dealing with two other cars on this matter ,can anyone help.
cheers in advance,a worried bluenose.

Pete Croney

We have seen this several times and it is almost always due to a failed front O2 sensor.

bluenosewrx

iTrader: (2)

thanks pete,what is the way to solve it without it happening over and over again?.and any idea on cost?.it is a MY02 model bought in belgium.

Pete Croney

When in 02? If its October or later, its under EU wide 3 year warranty.

Otherwise, its 300 odd quid for a front O2 sensor

scoobyboy

yep there is a modded ecu out now i have fitted three and so far it seems to work. the no. of the old ecu ends in 530 i think and the modded one ends in 531 dealer should do it under warranty if your still in and remember to take along both keys as they need to be programmed

Daz WRX

I appear to have a similar problem, only happens when accelerating through the gears, dealer has advised of a faulty neutral position switch which loggs as a misfire for some reason.
Which reminds me must book it in for that, if problempersists I'll push for the ECU replacement.

Cheers
Daz.

Pete Croney

If dealers are swapping 530 for 531 ecu's, this is well worth getting done. The 531 is much smoother.

Then again, if you've got an 01 with a 530, isn't it time you got it EcuTeked?

Daz WRX

Pete correct me if Im assuming this wrong but the 530 requires additional hardware before it can be EcuTeked whereas the 531 is purely software?

Looking to EcuTek fairly soon so if 531 makes things easier then I'll speak to Dealers.
Cheers
Daz.

bluenosewrx

iTrader: (2)

Thanks again pete,the car is a MY02 but i got it in Dec 01,so only got a one year warranty.mine also shows the light when going through the gears,it flashes then goes off ,then after this happening 3 or 4 times the light will come on steady.mostly happens in 4th gear.
If i get it Ecuteked will this cure it?,and then would i have to get a cat -back and some sort of induction kit to get the best out of the TEK? thanks in advance ,mac

Nigel H

I'll add my name to the list as well MY01. I've had several CELS with an engine misfire on cylinder one.

Happens to me when the engine is pretty hot and I give it some gas

Pete - does the 02 sensor just *fail* or does it give some warning?

Pete Croney

DAZ

The differences are software only and with EcuTek you can turn a 530 into a 531.

Mac

I still think your problem is the front O2 sensor. I had the same on mine and have seen it on several customers cars.

Pete Croney

Nigel

It just slowly gets worse. The ECU uses the front O2 sensor to look for misfires, by reading spikes in unburnt fuel/gas passing the O2 sensor. When the sensor starts to fail it gives the readings as though there has been a misfire and the ECU adjusts accordingly. Its this adjustment that gives the hesitation and rough acceleration.

By measuring the time difference between the spike and the last cylinder to fire, the ECU works out what cylinder misfired. Clever stuff, when it works right.

Daz WRX

Cheers Pete, EcuTek it is then I suppose, shame that group buy isnt a little further south.
Daz.

bluenosewrx

iTrader: (2)

cheers pete,looks like i'll be joining daz for the tek,any excuse lol.

EMS

Pete,

It´s the cranck position sensor which "looks" for misfires! Small differences in rotational speed will cause the CEL to light. A lighter flywheel is enough to introduce small differences in rotational speed and the cause of a misfire code. Unichips also tend to disturb the ECU because they "modify" the cranck sensor signal to change the ignition timing. Some cars are more sensitive than others......

Mark.

bluenosewrx

iTrader: (2)

My god! their is some really brainy people in here,my mechanic ability goes as far as changing a wheel.but seriously thanks for the input guys,still don't know the answer.tek it and see i reckon.

Pete Croney

Hi Mark

I have cured the problem on several cars, including my own, by changing the front O2 sensor. I have seen cars with faulty cam and crank postion sensors, but the problem is quite different and you get an error code for these. The front O2 sensor drops out of tolerance, reports misfires which aren't happening and does not create a fault code.

On my own car, I had tried a Link ecu. When I removed the Link, I had terrible misfire problems, with 2,3 and sometimes all 4 cylinders reporting misfires. The front O2 sensor was totally dead. Link uses the rear O2 sensor as it can't (couldn't) read the wider band voltage from the front O2. Consequently it ignores the front O2 and doesn't bother enabling the heater circuits. If wide band O2 sensors are not permanently heated, they die very quickly. Mine was completely dead, but during several weeks of trying to find what the problem was it never gave an error code for this sensor. It still gave readings too, just scaled down a bit from what they should have been.

I am intrigued by your comment about the lightened flywheel, as I cannot imagine any situation where fitting one could affect a sensor that sits at the opposite end of the crank shaft. The speed that the lobes pass the sensor has no bearing on its ability to trigger, provided the rev range is not wildly changed.

Its almost as though the 01-> ecu was designed to counter a Unichip. I have had cars in with almost every error code going, flagged up. They drove OK, but god knows what you would do if something did go wrong.

Miniman

iTrader: (2)

I'm really no expert, but isn't the crank constantly rotating at different speeds? How will the sensor (or rather ECU), know that the the crank changing speed slighty, I'm guessing its some sort of tiny hesitation, is a missfire? Couldn't you get that sort of problem for other reasons. Anything not working for the whole of the inbound and burn process may cause a hesitation.

Surely the best way to detect if a cylinder hasn't completed the burn is to test what's in the gases (because they should normally change). If one reads something abnormal (no burn) then the ECU knows there was a misfire.

Also I have an MY02 model, I don't seem to be having any issues, should I be asking for an upgrade to the software?

EMS

The misfire code caused by a lighter flywheel I didn´t experienced that myself, but I read about it on the US forum. If the system is already sensitive (which it is actually) it´s likely to get a misfire code after installing a lighter flywheel, which causes the rotational speed of the crank to change more easily. Very logical explanation in my opinion.

It is true that the misfire code is generated by sensing changes in the rotational speed. (detected by the crank sensor) Perhaps it ALSO uses the front O2 sensor, but that´s something I didn´t experience. (however I´ve seen WRX with broken front O2 sensor without misfire codes, but that is no proof)

Mark.

scooby L

Sorry to butt in, but could this symptom also happen on an MY03 STI?

Reading the posts above I positive that the same things are happening when I am going up the gears.

When the car had it's decatted downpipe the CEL fix was wired incorrectly, and as a result the boost was cut by the ecu. Eventually this was worked out (with much help from Pete) and the correction made by the dealer.
Now I am getting an intermitant CEL flash when driving, sometimes staying on all afternoon, along with rough acceleration between 3000 and 3500 rpm.

Could the o2 senor have been damaged when the CEL fix was wired incoreectly?

PS

I have had the CEL fix box changed once and the problem is still arising.

Pete Croney

Mark

It still doesn't make sense to me, as you will never accelerate the engine as fast as if you rev it when stationary. And this is something that does not upset it.

Scooby L

The CEL flashing on momentarily is a classic symptom of a failing crank, or most likely, cam position sensor.