Over rev between gear change.
 

Hi, I've got a 2002 wrx and when I change gear the revs increase by about 300 to 500 before they drop and it does this whether im booting it or just driving it steady, I have tried lifting my foot off the throttle but nothing seems to cure it, I've read different post's saying it could be the iacv and have brought a new rubber seal/gasket ready for when I take it off to clean it, does anybody else have this problem and does anyone know how to fix it.
Any advice appreciated.
Thanks in advance.

Slack in the throttle cable?

Really, could that cause the over rev, there seems to be 2 cables so is it possible that there is some slack in 1 of the cables.

when its idling, blip the throttle and see if the idle goes up and stays or if it hangs a little then drops,

if it hangs and doesn't drop(the revs), get the top of your foot, stick it behind the accelerator cable, and pull back, towards you.

let us know if that helps in bringing it down.

My old WRX Blobeye '05 had exactly the same issue after aboyt a year of ownership. Andrew Carr made one or two tweaks and sorted it but I couldn't tell you what he did, I believe it has happen to a few cars on the forum.

Sorry I can't be more helpful

I had this on my Evo, Its called throttle hang, where the revs hold or slightly rise during gear change. It was more noticeable after a mapping season and a tweek to the map helped but didn't cure the problem.

However I did fix this and figure out what the cause was :)

My actuator was week and not holding the the flap to control the boost due to a weak spring.

As I was going for more boost and the standard actuator was on its way out I changed it for a forge actuator and the problem was solved.

I put up with it for 8 months before getting to the bottom of the issue, Hopefully yours could be the same problem.

I'm glad to see this thread appear as I have exactly the same issue!

Thanks sti-chris... I'm going to have a look down that route before I take it to a specialist :).

Running Lean.

I had the same problem. about 500 miles after it started happening EML came on and logged a code with o2 sensor.

Replaced with a genuine Sensor, problem solved.

Did you replace the front or rear sensor? Mine is very similar, thanks.

It was the front one.

I was wondering if you have had progress with this issue, dude?

No luck so far, but I've got a new iacv rubber gasket so im going to take the iacv off the weekend and clean it and the throttle body and see if that makes any difference, I was talking to Jag at Subaru City today and he said it could possibly be the iacv or maybe the throttle position sensor, anyway I'll clean the bits the weekend and put a post on to let you know if it cured the problem. Thanks for asking and I'll be in touch.

That's great dude, thanks very much! How'd you get on over the weekend?

Hi all, I've had some luck and fixed the problem, I've put bigger bore ( 6mm ) pipe from the bov to the boost gauge and done away with the 4mm pipe they sent with the gauge and this seems to have worked, the boost gauge has started working again and the revs drop how they should do in between gear changes, so that's what was causing my problem, too smaller bore pipe. All's back to how it should be. Hope you others get yours fixed without too much trouble.
Thanks all.

That's great! Glad to hear yours is all sorted... mine is completely stock, no gauges etc, so mine's unlikely to be similar to yours in that respect. The hunt continues :).

Could that really be the cause ?

Can't see how that would cause this ?

Perhaps old pipe was leaking ?

Hi all, while changing the vacuum pipe has solved my problem, I also took the iacv off and cleaned that out by spraying nearly a whole can of carb cleaner through it until all the black carbon was gone and the carb cleaner spray was running clear. Cleaning the iacv may well have helped cure my problem but after testing driving the car on a short run the over rev problem was still there, but not as bad, but when I changed the vacuum pipe as well the bov started working properly again and the over rev problem has gone, so on saying that it's a mixture of doing both jobs has cured my problem and by just cleaning the iacv valve on someone elses car could eliminate there problem, all I can say is, if you've got an over rev problem clean the iacv and see what happens because you've got nothing to lose only the price of a new rubber gasket.
Good luck and I hope this helps.