Intemittent high idle. Stock UK FD

ianelvar · August 24, 2009, 08:06:41 PM

Finally got it nailed. It\'s time to play \'spot the problem\'

SmbFD3S · August 24, 2009, 08:08:29 PM

Lol i\'m assuming thats never been off the car then ?

ianelvar · August 24, 2009, 08:09:52 PM

You\'re right, I\'ve never had the TB off this manifold. I found that the bolts weren\'t torqued up very tight, which explains the damage.

SmbFD3S · August 24, 2009, 08:12:43 PM

Well i got some some 3mm gasket paper and made my own, cheap enough at a fiver for an A4 sheet

ianelvar · August 24, 2009, 08:14:53 PM

I did get some weirdness after fitting it. I found that it would still idle high, but in a more consistent fashion, and it didn\'t run like crap. If I blipped it would come back down properly every time, or if I pulled the clutch up while in gear and dragged the revs down it would stay. Very weird. After an ECU reset it\'s been perfect, so it must have learned some weird way to use the idle control valve while it had the air leak.
I would have done similar with the gasket paper, but I happened to have a metal one spare.

SmbFD3S · August 24, 2009, 08:17:58 PM

Well glad you\'ve managed to sort it mate anyway

now just bypass the throttle body heater and save on the high startup idles (when you wire the lever out the way) lol and you\'ll see a couple of degrees lower inlet temps too... Oh and it cuts down heat soak MASSIVELY....

Then when it gets cooler just reconnect the hose

ianelvar · August 24, 2009, 08:22:28 PM

Oh, and one last thing. I\'ve learned while playing around with this that air going past the double throttle plates is effectively \'unmetered\' if the single throttle plate is closed. The map sensor connection is only in the lower channel, so the ECU doesn\'t really see a difference in pressure significant enough to imply any more air flow. This is why it was running rough - the leak is straight past the secondaries. Try pushing the double plates open while it\'s idling and you\'ll see it go really lean and hunt.

To a certain extent you can modify the idle mixture by using the throttle stop for the double plates on the TB. Be careful because it\'s VEERRRRYYY sensitive though. Not totally relevant to the original problem, but I thought worth mentioning all the same.

ianelvar · August 24, 2009, 08:25:51 PM

Quote from: SmbFD3S;637260Well glad you\'ve managed to sort it mate anyway now just bypass the throttle body heater and save on the high startup idles (when you wire the lever out the way) lol and you\'ll see a couple of degrees lower inlet temps too... Oh and it cuts down heat soak MASSIVELY....

Then when it gets cooler just reconnect the hose

I was thinking about giving that a go actually. While I had it on the bench I set the screws so it only opens the throttle a tiny crack anyway, but it would be good to lose the heating effect too.