Luis de Prat

I just got through replacing the idle stabilizer valve (ISV) and throttle position sensor on my 951 and had to readjust the idle screw. The car was shutting down during sudden stops because I had fooled with the idle screw previously to test for the leak in the ISV.

So after opening the idle screw about 1 turn, I'm getting a hissing sound from underneath the driver side intercooler pipe, right next to the AFM.

What could be leaking in that area? I've checked to see if the sound comes from the blow off valve or the lower intercooler pipe hose, but the sound seems to be coming from below the pipe itself.

What else should I check? Thanks.

David Floyd

Vacuum line on the underside of the throttle body is one thing to check

potent951turbo

I have seen another 951 have this EXACT same problem. I had always heard it but when I went to set the idle for them I was playing with the adjustment screw and turned the idle way down and the hissing in that area was very loud but I could not pinpoint it at all. I double checked all the vacuum connections and they were all fine, even the one under the throttle body. If you find the cause please report to us what it is.

Luis de Prat

Hey, thanks for the response. It's been a long, frustrating road getting the boost back to normal on this car.

First I was getting an on again / off again boost situation which turned out to be a bad Cycling Valve.

Replaced that, and suddenly the Idle Stabilizer Valve started leaking like crazy and making the idle very erratic.

Replaced that and everything seemed "normal" but I could hear a slight whistling sound coming from below the IC pipe when pushing the accelerator cable back.

Had to open the idle screw a bit because the car was shutting down at stoplights, and now the sound is a constant whistle from below the IC pipe...

Hope to take it apart today or tomorrow and see what I come up with. Keep the suggestions coming!

tommye

Hey Luis !
Haven't been too active here for a while - too busy with other things....:-(
Glad to hear that the main problem is fixed - running with infinite turbolag is no fun !
As others have pointed out, there is a quite small vac. hose under the TB - you should not need to take much apart to check if it's ok.
Are you setting the idle screw correctly as indicated in the factory manual?
i.e. with warm engine and in the round diagnostic connector near the brake booster: 2 of the pins shorted together (can't remember which ones right now - will look up if needed) to disable the idle stabilizer.

Hope it works out !!
Tommy

PS You've got a pm

bearone

you need to make sure the idle stop screw is adjusted properly before any other adjustments.

87951