Whistling AFM !

[DaveG]

My Griff 500 has just developed a high pitched whistle emanating from the AFM. It has done approximately 1000km following an engine rebuild and I am still fine tuning to match a new cam, etc. This whistle started today and is there most of the time right down to idle. I have checked for leaks and this does not appear to be the problem. Car running ok (except for high idle and some shunting which I am trying to eliminate through timing and base idle.)
Anybody come across similar symptoms with AFM? Any thoughts - not too many moving parts !

[kbear]

Hi Dave, my 500 had a screaming whistling noise from around the AFM and plenum when the intake hose had completely collapsed down the front near the radiator. The collapsed hose was causing air to be sucked in through the joins near the plenum and AFM. It’s amazing how much vacuum can be created by the engine. I hope this helps...

[DaveG]

Thanks Anthony. The "jet whistle" is still there when I commpletely remove the intake pipe. A search for "whistling" on Forum leads to the suspect base idle. I will try re-setting tomorrow and see if this cures the problem.

[V8 GRF]

DaveG said:

Thanks Anthony. The "jet whistle" is still there when I commpletely remove the intake pipe. A search for "whistling" on Forum leads to the suspect base idle. I will try re-setting tomorrow and see if this cures the problem.

I believe you need to be very careful when adjusting the base idle or you can royally 'bugger up' the running of your car.

[clive f]

I had the same problem a while ago, Joo at trackcar reset the base idle and the noise dissapeared.easy to do and shouldn`t give you any running problems.

[spend]

I can't see the problem adjusting the base idle? All the crud that builds up in those passages would suggest to me that the idle screw needs gradual opening just to maintain the bypass volume? I can imagine the idle going through the roof when the plenum is cleaned out..

[andyy]

Mine whistles if the base idle is wrong
Unscrewing the hex adjuster - anticlockwise - on the top of the plenum stops it

Andy

[DaveG]

Just to close this topic. Base Idle was the source of the whistle. A clockwise turn has removed the problem and slightly improved the "light throttle shunting below 2000rpm". I anticipate fine tuning of base idle and timing will eventually result in smooth throttle control and I can then move on to Megsquirt installation.