High revs on idle

[deadlegs]

G'day guys.
I got my 08 GT Spec B serviced last week and since then have been having higher than normal idle revs. It only happens when I slow down to a stop, like pulling up at the traffic lights, and I take the car out of gear and coast to stop. The revs drop down like normal when I take the car out of gear then quickly go up to between 1500 and 2000 for a few seconds and drop back down to normal idle again.
I took it to Subaru today and after an hour and a half they told me that it was because they reset the ECU when they serviced it and the computer has to relearn its idle postions etc again.
I was just wondering if this is a normal thing to happen after resetting the ECU or do you think Subaru are bull shitting me?
Any help or advice would be greatly appreciated.

Adam

[jp928]

I have never seen it after a service....but - a while ago I had a similar issue one day in traffic - got slowed down, threw it into neutral, idle jumped up, gradually came down as I slowed to a halt. As soon as I started rolling again, out of gear, no throttle, idle lifted again up around 1300rpm. When I got to work, I disconnected the battery for a few mins, reconnected, problem gone, and it ran better to boot. Try that...unless dealer fixed it?
jp 08 gtb 6mt wagon

[Shaheenis]

I had this a few weeks back after re-flashing the ECU with a new tune. I suspect it was the tune so flashed it back the next day. I suppose it is possible that it was just the ECU learning..

[dr20t]

If your maf scaling is out it will cause this to happen until your ecu relearns some fuzzy logic parameters.

However of concern is why your maf scaling is out if you don't have any mods (or at least no mods were made by Subaru at the time of service) to change your engine's airflow /fuel requirements

I suspect it would be a vacuum leak from when they did your upper engine cleaner maybe.

[senator]

I suspect it would be a vacuum leak from when they did your upper engine cleaner maybe.

+1 check the service report to see if thed did do a upper engine clean.

[eslampar]

I suspect it would be a vacuum leak from when they did your upper engine cleaner maybe.

+1 check the service report to see if thed did do a upper engine clean.

+1 Vacuum leak. Had the same issue with my old BMW

[deadlegs]

Thanks for the feed back guys, I really appreciate it.

As for upper engine clean, I don't think they did one at the service but they did do it about two weeks after when I took the car back in for them to look at it. The service man said the upper engine clean should fix it but its still no different so I'm going back in this afternoon.

If your maf scaling is out it will cause this to happen until your ecu relearns some fuzzy logic parameters.

However of concern is why your maf scaling is out if you don't have any mods (or at least no mods were made by Subaru at the time of service) to change your engine's airflow /fuel requirements

I suspect it would be a vacuum leak from when they did your upper engine cleaner maybe.

I have a exhaust and tune done by MSR and never had a problem until the most recent service by Subaru.
How do I check the maf scaling? Is it worth a visit to Bruce or someone with similar knowhow?
Cheers
Adam

[deadlegs]

I suspect it would be a vacuum leak from when they did your upper engine cleaner maybe.

+1 check the service report to see if thed did do a upper engine clean.

+1 Vacuum leak. Had the same issue with my old BMW

The car still runs fine with plenty of power on boost etc. What other issues could I expect from a vacuum leak?

[kiahatsiu]

Might be slightly altering your air fuel ratios when you under load too, as there will be unmetered air in the intake.

[Boostaddict]

Check the feed line into the top of the blow off valve . Mine came off and had the same issue !!!

[deadlegs]

Might be slightly altering your air fuel ratios when you under load too, as there will be unmetered air in the intake.

Would that explain higher than usual fuel consumption?

[dr20t]

If your car is tuned to suit the parameters then an ecu reset may be causing the erratic idle until it self learns the closed loop stuff under light load etc

I would clock up 200kms or so and see if it hasn't dissapeared then rethink it

Lets hope they haven't flashed your ecu back to stock (highly doubt they have done this)

[deadlegs]

If your car is tuned to suit the parameters then an ecu reset may be causing the erratic idle until it self learns the closed loop stuff under light load etc

I would clock up 200kms or so and see if it hasn't dissapeared then rethink it

Lets hope they haven't flashed your ecu back to stock (highly doubt they have done this)

I've done over 1000km since the service and its still happening.

[Robbks]

go outside, open the bonnet and have a look.

[dr20t]

Then there's a problem if its not gone after 1000kms

Self learning would've happened by now

Mick