Revs droppping at standstill

[Lord Ben]

Hi All.

Had my UKDM DC2 for a couple of months now, various work been done on it - turning into quite the project.
Something which has only recently come to light, once engine is warm and been running for a while (after a good 50 miles + driving) when pulling up at lights and returning to idle after a bit of enthusiastic (NOT ridiculous) driving, The revs have been falling away from idle down to around 500, maybe even lower. The engine hasn't stalled out yet, and i've tried sitting at standstill and playing with the revs.when this happens, revving to around 3.5K and letting them fall away,same thing happens, revs drop, then come back up. It idles stable, no fluttering.

Any ideas?
cheers

 

[hippy43]

Not to sure with the dc2, but the most likely cause on an ep3 is a dirty idle control valve. I had a similar problem a while back and it turned out to be this http://type-r-owners.co.uk/forums/showthread.php?75110-Electronic-Load-Detector-Circuit-High-Input and not an issue with the idle control valve. Don't thinks it's too common a problem as it doesn't really get mentioned on here.
Does the idle issues go away after a spirited drive?

 

[Lord Ben]

Not really.... once it starts happening, that's it, it happens. I've tried testing various rev patterns, right up to revving into the VTEC range and letting them fall. They fall so low, i have to bounce the throttle to kind of salvage the revs and keep em around 850, and the juggling can take best part of 10 secs to get it back stable again. I had a CRX which had a similar problem, but I never got to the bottom of it - someone suggested it could be either ISC, or may have been something to do with the PCV hoses being blocked....? Can't imagine why that'd cause this kind of problem, but heard stranger.