Jump to content
Sign in to follow this  
rich

wrx idle issue.....3500rpm idle-solved!

Recommended Posts

can anyone shed some light on my idle issue, or the fact my impresa wants to idle at 3500rpm? ive just refitted the engine after new headgaskets went in so I'm hoping its an air leak post throttle body but I'm honestly stumped, I have a little log of it messing about, any suggestions would be appreciated. only things I can see are its reading full lean on the wideband,even tho its revving its self up quite happily, and even setting the throttle plate angle to 0 doesn't stall it which I found kinda strange.i set the rev limit at around 2000rpm to try and save any engine damage so that can be seen in the log too,if it helps. not technically a link issue I know, but I'm stuck

idle fault.llg

Share this post


Link to post
Share on other sites

I think you're right with the air leak theory. at 1.1% throttle and 23* ignition angle you arent going to idle at 1700rpm normally. Assuming your base timing and TPS calibration have been checked. Does TPS read 0% when you press the throttle blade shut?

If you put the gasket between the throttle body and the intake manifold on upside down or back to front you can get an air leak around one of the edges, at least on the non-ethrottle ones you can anyway as it creates a leak to the passage where your idle valve would run air through. 

try spraying ether at various points of the intake manifold to try figure out where its leaking, wherever it revs up is where the leak is. Or if you've got an air compressor try setting the engine to TDC to close up the intake valves, then mostly sealing up the front of the throttle body with rags or a stretched our section of bike tyre tube, then feed it some compressed air at 10-20psi. it should hiss out any leaks and to run at up to 3500rpm you should have a pretty big leak.

Did you remove TGV's and not seal up the holes from the butterfilies maybe? You havent specified which engine you are working with.

Share this post


Link to post
Share on other sites

thanks for the reply cj, its a 2006 dbw ej255, the intake mani and throttle body are as removed so shouldn't be that gasket, haven't took the tgv's out either, only gaskets disturbed are the main intake manifold gaskets. I can hear an odd high pitched sound from one side of the engine so I'm assuming a leak, I get zero errors and have gone through throttle calibration a couple of times. could an intake leak cause such a high rpm though? thanks alot

Share this post


Link to post
Share on other sites

depends on the size of the leak, but yeah at idle it doesnt take much air to bring the revs up to 3500. 5-10% throttle opening would probably do it depending on ignition angle so that gives you an idea of what you are looking for. Tearing or pinching the gasket on the alignment pins would probably do it.

Between the lean lamba, a hissing/whistling noise, and what sounds like correctly calibrated throttle, it sounds like a leak is the most likely scenario. Spray some ether/brake clean/anything in an aerosol can that you can light with a match, and if the revs go up or obviously change in sound thats your issue.

Share this post


Link to post
Share on other sites

ok cool, thanks a lot for your help, ill go and have a play. if it comes to it, ill take the mani off again to see what state my gaskets are in. fingers crossed its a pipe somewhere but I kinda doubt it

Share this post


Link to post
Share on other sites

One of those little vacuum hoses wouldnt be enough of a leak for 3500rpm. Something like your brake booster hose might be, if you are lucky and its not a gasket...

Share this post


Link to post
Share on other sites

well I loosened and re tightened the gaskets and it seems to have more or less cured it to so I suppose the manifolds coming back of for new gaskets, don't want it happening again. thanks for your help, top man

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
Sign in to follow this  

×
×
  • Create New...