Thread: Throttle butterfly adjustment

Originally Posted by scruffy

Hi All, just wondering what the correct procedure is for adjusting the throttle butterfly on a 3.5 V8 93 Disco. Tried the allen key on top of the throttle butterfly/phelenum and can only get 2 turns [approx] with no perceptable change in the position of the butterfly. Read somewhere that the gap should be .5mm [I think] but I cant get the smallest feeler gauge in. Also read that the throttle plate adjustmen is done by measurement so am at a loss. Thanks for any help. Bob

Allen key adjustment does not physically shift the butterfly. By unscrewing it you open an air channel around the butterfly. Why are you trying to adjust the butterfly? Unless it is sticking in the bore (then clean it) you should leave it right alone.

Reason for adjusting is because of what I read and then performed a check just to make sure that all was adjusted correctly. Now that I know that by adj the allen key does not adj the butterfly, Ill leave it alone.. I suppose the old saying.....a little knowledge is dangerous....can apply in this instance to me.. Once again, thanks very much for sharing your valuable knowledge Bee Utey, much appreciated. Bob

Originally Posted by bee utey

Allen key adjustment does not physically shift the butterfly. By unscrewing it you open an air channel around the butterfly. Why are you trying to adjust the butterfly? Unless it is sticking in the bore (then clean it) you should leave it right alone.

What is the correct adjustment for this screw please? That is, how many turns out should it be?? Bob

Originally Posted by scruffy

What is the correct adjustment for this screw please? That is, how many turns out should it be?? Bob

Someone else will probably know the exact procedure, but I generally adjust it so that the range of operation of the idle air control valve keeps engine speed within a good range, i.e. not too fast on startup and not too slow for occasional stalling to occur. It often needs to be adjusted after an ignition timing change.

Thanks, that is what I have done. Just thought that it may have to been adj by 1/3turn etc. Bob

The proper way to adjust it is to block off the stepper motor to plenum pipe at both ends and then adjust the screw to get an idle of about 550rpm.

To block the two ports I use some rubber end caps like you would find on the end of a walking stick. You can get them in the right size from Bunnings.

If it isn't adjusted properly then the car either stalls sometimes or the revs stay high between gear changes until you come to a stop and the VSS tells the stepper to get the revs in check.