simonds1

Hey guys. I have just been searching on here and there have been plenty of people posting about the same (or at least very similar) problem that I've got with my impreza, but the threads never ever seem to get resolved so I'm still none the wiser

Basically, my impreza has recently started to idle quite poorly in the mornings. I don't know is it down to the much colder weather or if that's just coincidence. I had an alcatek ecu fitted in the summer so this is my first winter with that ecu. If anyone fancies watching the world's most boring video, here is what it idles like in the mornings......



It takes literally 2 minutes for it to find a smooth(ish) idle and settle down. If I try and drive away within those 2 minutes while it is hunting around for idle, it is pathetic - always wanting to cut out (but never actually does) at junctions etc, and quite hesitant in accelerating. It kinda feels like someone has taken away the initial part of my throttle pedal, it seems to do nothing and feels really unresponsive. On light throttle it's very 'surgy' aswell. If I let it warm up for 2 minutes until it's found a smooth idle before I drive away tho, it's okay(ish).

The main other symptoms are a very fuely smell when I start it, and horrific fuel consumption. I normally get around 280 - 300ish miles on a tank, and I got 174 miles out of my last tank!! It's literally killing me, it's ridiculous.

From what I've read on here from people with similar problems, the main options seem to be coolant temp sensor, oxygen sensor or idle control valve? I was also thinking maybe throttle position because like I said earlier it sometimes feel like someone has taken away the initial part of my throttle pedal. But then it's not as bad when it's warm so I'm not sure about that

Any opinions would be hugely appreciated, thanks guys

Hawkeye D

Air flow meter (MAF)?

Quite a relaxing video actually, with birds twittering and the sound of running water lol!

Hmm, it's not happy is it, then picks up towards the end. I doubt it's serious, it will be a sensor of some kind I'm sure. No CEL then? Looks like steam coming out of the exhaust (no smoke) so that's cool.

Perhaps try an ECU reset which involves disconnecting the battery for a bit (I think).
Someone will see this video and pinpoint the problem I'm sure.

jura11

iTrader: (7)

This ECU(AlcaTek before named SimTek) is Mafless


Jura

jura11

iTrader: (7)

I would suggest speak with your mapper about this,its pretty common(Cold idle or cold start) on the SimTek or AlcaTek and this can be resolved easily by your mapper by map tweak


Jura

leecalcars

iTrader: (37)

Cols start mine does it settles down after 5 mins or so wouldn't worry about it

simonds1

Appreciate all your replies so gar guys, thankyou Yeah as mentioned earlier I've got an AlcaTek ECU now so it doesn''t use the MAF sensor anymore, and also doesn't report any CELs! Lovely. Lol.

It's not so much the car's behaviour that bothers me anymore, I mean I've got used to it now. Alltho it does suck having to start my car and wait before I can drive away. It's the fact that it's literally nearly consuming twice as much fuel as it used to, and it is financially killing me!

alcazar

iTrader: (2)

I would also speak to your mapper.........if it was mapped in very hot conditions, it may need to go back and be looked at again from stone cold.

simonds1

Hi guys, sorry have been ages replying to this. I have been back to my mapper for an adjust from cold so I don't think it's that. My fuel consumption is literally double what it normally is. Well, near as damnit. When I fill up, by the time my fuel gauge gets down to half, it's normally done around 150 miles, and now it's about 80 every time. It's ridiculous! I don't think a map that hasn't been adjusted for cold running could effect the fuel economy that badly could it? Not sure Gonna probably just try changing the coolant temp sensor and see if it makes any difference, because it's only £27

madscoob

iTrader: (3)

oxygen sensor , doubles fuel use and the fact that the throttle does nothing if you press down normally and nothing happens, get the voltages checked on your 02sensor , ive just changed mine and its like a new car, and i had exactly the same problems as you

Jolly Green Monster

iTrader: (4)

Does sound like it could be o2 sensor if suddennly doing it.

simonds1

Thanks for your input guys I understand the coolant temp sensor can affect fuel economy if it's faulty aswell though? Or can it not affect it this badly? It's just the oxygen sensor is £160 and the coolant temp sensor is only £27, so it makes sense to try the much cheaper one first surely?

madscoob

iTrader: (3)

get on to mattybr5 on here or scooby spares both of which will sort you out a know working genuine part, do not use one of the copy parts they last 12months tops. even the bosch universal with conversion wiring only lasted me 12months

Jolly Green Monster

iTrader: (4)

Get your mapper to plug in and check. No point replacing what it might be.

simonds1

Unfortunately, my mapper is a 4 hour drive away so with my current fuel consumption, it would be cheaper for me to buy both sensors and replace them, than to actually go and see him for him to check

I have a feeling this is going to be an incredibly stupid question, but......If I unplug my oxygen sensor and try and drive the car, what should happen if it's faulty? Will it make a difference or not? To the driveability I mean, not the fuel consumption. Could I diagnose it that way?

Jolly Green Monster

iTrader: (4)

I would expect it to be doing the same now.. ie. no signal so thinks its lean and throws fuel in..

jason_2013

If you replace the O2 sensor, isn't it the wideband you want to replace not the oem one. If so those wideband sensors are less expensive than the oem versions. Then you need to check what wideband system was fitted. The bosch ones aren't too expensive.

Usually though proper diagnose is cheaper in the long run if you don't know how to check sensors.

Jolly Green Monster

iTrader: (4)

I assume he has the normal install and is using the oe o2 lambda sensor thats a narrow band in the top of the downpipe on that car.

simonds1

Yes that's correct. I have the original genuine subaru 02 sensor installed in the top of the downpipe and that's how it was when it was mapped etc.

simonds1

Well, I say 'the original', but I have changed it since I've had the car because it was failing the MOT on emissions last year. I just got it 2nd hand off ebay though, not brand new

Jolly Green Monster

iTrader: (4)

So that could be the issue

simonds1

Yeah, Just to confirm though - it's not something that started happening when I changed the 02 sensor, it's just a recent thing since it's got colder. Madscoob sent me a pm saying what voltages to check on the sensor etc so am gonna try and get hold of a voltmeter and do that as soon as I can

jason_2013

Bear in mind when testing the sensor that it will take a couple of minutes to start switching . Initially will be reading .45 until warned up enough.

rwb123

having same issues on my v3 pretty sure its the lambda gonna unplug mine 2moz and see if that cures it can't do any harm and it only takes a a mo

Jolly Green Monster

iTrader: (4)

Unplugging it wont prove anything

rwb123

was told and i'm far from an expert and i'm sure you will correct me but the lamda sensor is only in play upto 3k rmp's ?

Jolly Green Monster

iTrader: (4)

Cruise and idle. There is an rpm and boost level the ecu ignores it above but depends what they have been set to.

Simon

rwb123

mine just a v3 wrx my97 air filter and full turbo back exhaust + decat bought it like that

Jolly Green Monster

iTrader: (4)

Standard ecu sti v3 will be around 3000rpm yes

rwb123

ok so does the ecu isn't receiving a signal from the 02 sensor will it have a std setting to work off ?

Jolly Green Monster

iTrader: (4)

No. The valid sensor range is 0 to 1volt so unplugged it reads 0volts and the ecu thinks it is lean and chucks in loads of fuel.
Hence my post that unplugging it will prove nothing.

Simon