K20A2 idle issues
 

Just thought I'd share a bit of handy info for anyone fitting a K20A2 that has been standing for a while.

The idle control valve on the k20, is notorious for seizing, and mine did exactly that during the time the engine had been sat unused.

If you find when you first start your car the engine is revving above 2k, the chances are your valve is also stuck. If your revs are running this high, it'll confuse the ECU and it'll think the car is an over-run scenario. This will mean the fuel will be cut until the revs drop to ~1500rpm, then the fuel will turn back on raising the revs to the previous level - it'll be a cyclic process.

The idle control vale is on the underside of the throttle body, and if you want to clean it you'll need to first remove the throttle body, then the idle valve.

Once removed, you'll note the idle vale unit consists of two parts, one plastic, the other aluminium. Seperate these, and you'll see the spindle that controls the airflow though the unit. To un seize the spindle turn it manually with carb cleaner or similar in the bypass pathway. I did this to partially free mine, then got the drill out and spun the spindle up with a load of oil in the bypass area.

This did the trick for me, and now my car seems to idle fine. It'll be interesting to see if that's still the case the next time I try to run the engine.

As an aside, and for anyone interested, the standard marlin silencer is pretty quiet on idle, with a reasonable rasp when the engine is revved. Not the best vid' as time was getting on when I took it.

www.johndry.com/sorted_idle.wmv

Jon - I saw your car today, and it's got a sticky bypass valve.

Care to elaborate on that one, Spoke to Terry today and its coming back on Thursday, so it will be back to work for me then.

It's doing exactly as mine did when I first started it, and cyclicly revving as described in my first post.

I told Simon how to fix it, but if it's not done when you get it back, you'll now know what to do.

As an aside your silencer doesn't do much! I think you'll need some more attenuation to get through the noise test at Combe - I assume they still require <100dBA @ 60% revs and 1m.

102db at 4500rpm at 1m yeah

For Racing and for Pre Race testing i believe its 108db, at 3/4 rpm so 6000, at 0.5m, Ill find out on Monday at the race ith Mark and Dylon, but the CC website states 108, so it will be over by the sounds of things but have to look into that, depending on how quick depends on the how quick next door start moaning.

John im guessing you hear it running and its a little on the loud side?

Yes I heard it running. It's massively louder than mine, and given what I've experienced I'd say it's got to be damn close to failing a noise test. It's a great deal louder than any of the cars that failed a 100dBA test a track day I did recently (even allowing for the fact your car was inside Marlin's factory).

If you've sensitive neighbours, you'll be getting to know them better very soon!

However it is running, so that's a result!

Lucky you, I think I may be borrowing my mates noise meter and seeing what it actually is, the car isn't going to be back with me for long, as its off to the body shop in a week or two.

Like you say it runs atleast its not a very expensive paper wieght, few!

Aaargh, this is driving me nuts now. Following John's invaluable tip, I stripped down my idle valve as my engine was showing those symptoms. Sure enough, it was seized, though fairly clean, and I easily freed it up - now moves very smoothly. However, the idle is still haywire. With the air cleaner off I can monitor the bypass valve position, and after a few seconds/minutes running (this varies - sometimes doesn't go wrong until I blip the throttle) it persists in opening up the valve considerably - which promptly sends the revs up and the engine back into its fuel cut / cyclic idle. If i take the actuator off and manually close the IACV to give a steady idle, I can then idle it up or down happily from K-Pro and all seems well. As soon as I connect it up again, revs go all over the place. The actuator is obviously working one way or another so I don't think the valve is faulty, but I'm a bit at a loss.

John - did you have to do any set-up after cleaning the valve to allow the ECU to re-learn? Anyone else experience this?

Richard

Rich,

I had to clean mine 3, maybe 4 times. Every time I was surprised at how much muck came out.

Have you got your primary lambda sensor working? Mine was playing up (not hot enough) and this caused idle issues when my engine was warm.