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Cold Idle

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Past couple of days the car has been idling a little rough while cold


Once its warm runs fine


Had a look around the engine bay for anything obvious but cant  see anything


Anyone point me in the normal locations to look? 


What I did see was the lambda sensor on decat downpipe being in place but wire cut off, there are no warning lights on dash. Could this be bypassed in ecu or something?



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When you say rough, fo you mean erratic or just high upon start up ? If it's just high 12-1500rpm then takes a little to drop below 900 it's normal.

Not sure about the lambda, mine was fooked and only threw up a cel light when giving it the beans, not sure if a remap would be able to by pass it. Have you had a look fpr historic codes stored in the ecu by using the green and black plugs under the dash ?

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I normally in the morning go out the the car and switch it on, then go in and collect my things for work. Just to give the car a little time to warm up


I just start it from outside the car, when I turn the key the car doesn't seem to have a steady enough idle and it conks out. I just start it again and it will start ok but I need to leave it a few minutes for it to run ok


Something isn't right somewhere, hoping its an easy fix


No I havent had a look for codes. Where about under the dash is the plugs? 

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Do you know if it's running mafless in which case you do get a bit of idle fluctuation due to the ecu only using the map sensor to calculate the incoming air .

Still it shouldn't stall if set up right but if the car was driven to the mappers they wouldn't have been able to map the cold start as it would have been warm before they started.

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I don't think it will loose the map though, just plug the black ones in for now and see if the check engine light just throws anything. I've recently had some of the parameters changed at a garage using the subaru select management tool. Did an ecu reset by mistake disconected the Battery for half hour but everything stayed the same.

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Sent an email to the company who mapped the car, they have come back with this:


Martyn would very likely have some stored data on the car, although it may not have much bearing on the way it is right now.
Mapping is unequivocal, in that any settings are going to stay the way we left them in terms of relative output. I can only assume it was ok previously, or the man would have been back for another go!
Any mapping can only be long term successful if everything associated with the car’s management system remains in good order. The Alcatek has full closed loop idle control and should stay where it’s put.
A few examples of failures leading to idle problems;
Air leaks from gaskets or hoses
MAP sensor faults
Throttle pot faults
Lambda sensor faults
Idle valves sticking
Wiring issues
Leaking injectors or injector seals
There have also been rare instances of track failures from the ECUs.
You have a couple of choices to deal with it, either bring to us or take it to another person to check it out. If anyone else wants to map the car they can do so, but they need to obtain the codes from Alcatek to allow it, then they have to set it up from scratch. (This isn’t our doing, incidentally)
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If thats engine tuner martyn j then he's a respected scooby specialist (from what I've read).

I just thought it was a possibility what with not knowing it's history and the recent drop in temperature .

Maybe just have a squint at a few of the things listed above.

Check for leaks/perished vacuum pipes.

Throttle body is clean.

are the spark plugs/service due.

Give the idle control valve a clean .

Check dumpvalve and fmic pipework are not leaking .

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I just wanted to know what exactly they had done to the car more than anything else


I will be replacing the FMIC soon anyway would be handy if that was the problem :) Will also replace the DV at the same time

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Right just plugged the black plugs together and I get nothing seems to happen


I connected the black plugs

Then turned the ignition to on

I then have to press my immobiliser for the lights to come on

When I do that the car just does its normal 


Check engine light just stays lit 


Am I doing something wrong because there is 100% issues with the car somewhere :(

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I have ordered some new silicon vacuum pipe. Just going to replace them all 


Also putting it in to a guy who lives close at the end of a month to have a good run over it. He knows his impreza's so hopefully get to the bottom of everything

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