IDLE making me tear my hair out!!!

My saga continues!!!

EVER since I decided to replace the split vaccuum pipes with some new ones and to remove the cam cover vent pipes to fit an oil catch tank, my beautifully Emerald tuned engine has really turned into an unruley teenager!

I am still to resolve the fast 2000 RPM idle on start, but think it is definately the IACV… as when unplugged from cold this problem goes away.

Once warm however, the idle is all over the place! IACV plugged in or not!!! It settles nicely at 1000, then runs up to 1500, then back to 900! Both stationary and when moving…

When I ‘rev’ the engine, it picks up really cleanly, but then the revs drop off slowly like some boggy 1.6 Vauxhall… gone has the sharp return to idle that i used to have!

Just cannot work it out! The car was mapped at great length my Dave Walker, so why should replacing a few vaccuum pipes and cleaning the TB’s etc have caused all of this!!!

Please HELP!!!

Just don’t let it idle ! …

Sorry Pete … unhelpful I know

Could always fit a Honda ?

It sounds to me like the fuelling is awry. Like I said before 10 minutes with someone who knows the ECU will have it purring, you will need to use a PC and the emerald software to get anywhere.

Here is a procedure I use to perfect the idle.

Use the following procedure to set up the idle and corectly align the pot/map. It’s been developed over many many sets of TBs and works.


Turn off idle control in the software!!!
Make sure the engine is hot
Make sure the idle advance is no more than 5 degrees,
Slacken the locking nut on the balance mech


i) make sure there is some slack in the cable.
ii) measure the airflow between TB 1 & 2 against TB 3 & 4.
iii) if 1 & 2 are low, increase by turning the balance grubscrew clockwise, if 1 & 2 are high reduce by turning counter clockwise. If they balanced lock up the adjustment grubscrew and ensure you have 1000RPM, if they are balanced and at 1000RPM go to viii)
iv) adjust the overall idle adjustment screw if idle falls or rises too much, set idle to 1000RPM
vi) if you have adjusted the overall idle adjustment screw then make sure you re-align the throttle pot in the software immediately.
vii) go to i)

viii) Let the engine idle and go to the live adjustments screen

Look at the lambda scale and adjust the fuelling until it shows two or three bars into the yellow, try trimming the fuel up and down two or three points and note the point at which the idle starts to fall in either direction, then go for the middle point which should give a clean and reasonable idle. If the idle starts to fall when you are adjusting the fuelling then you are going in the wrong direction, start adjusting in the opposite direction, The fuelling is right generally when the idle is at its fastest, if the Lambda scale doesnt appear or appears way off then it could be that your sensor is faulty. If the idle speeds up , adjust using the idle adjustment screw NOT the fuelling or timing, reset the throttle pot each time you adjust the idle screw. Recheck the balance.

When you have the idle stable and smooth at 1000RPM and the lambda reading consistently in the yellow by 2-3 bars then the idle is OK. Reset the throttle pot and set idle control on in the software with values of 25 degrees and an update rate of 10, then all should be well.

It might take a while to go round the cycle a few times, be patient, take your time, its worth the effort.

If you dont have a near perfect idle then you have not followed the above, I have never known it to fail.


PM sent!