|
Hi,
I believe you are thinking it was a sudden in rush of air. Since you just had to hit the brakes it seems very logical.
The check valve is a simple device but they do crack on the very front face when very old.
The test I do is wiggle it while it is in the grommet to see if I can get it to hiss.
The grommet has to be kept in good condition and if so it will hold a vacuum for a very long time. It’s big!
It should be holding that vacuum after every engine shut down.
The test for these type check valves is for you to blow air only in one direction and not in the other. I do a mouth test for the sake of simplicity, not for any specific flavor! (:)
The Same thing can be done for the vacuum bottle system in the cabin.
You will see a check valve for it above the intake manifold.
I used a hand held vacuum pump with a gauge to check the entire system of things in the cabin.
I look for a leak down as this area can affect mixture control, if bad enough.
A empty vacuum reserve bottle can cause harder starting or lack of an instant control of the idle speed. The engine needs to unfill that bottle so, it temporarily has a leaner mixture for that amount of time.
A bad brake booster diaphragm should make a hiss sound when the brakes are applied. Sometimes it can make the idle change if the IAC cannot catch it. The IAC has a limited flow range around the throttle body plates proper opening which is just barely above stalling and below the 750 rpm.
A proper working IAC will shoot the idle above the 750 and immediately bring it back down if the throttle plate and th Throttle Position Switch is set correctly to say idle!
Make sure the throttle plate in the bore is closing all the way shut.
The stop lever on the shaft should only touch down on it and not hold the throttle plate open more than an extra 1/4 turn after contact. We only want to keep the plate from jamming under return spring pressure.
We want all the of idle air amount needed to go through the Idle Air Control.
Check the TPS with an ohmmeter to see if It is changing state when it clicks.
While this is all apart do an inspecting of the according hose behind the AMM.
Look for cracks or rubbed spots on and in deep of the volutes. Shine a light from the inside.
Take note that the clamps seal well at both ends upon reassembling.
After you are confident that the bore is clean and adjusted correctly go test drive it. You want to repeat the experience you saw the problem under.
If it keeps doing it?
Try cleaning the IAC. Testing it with a small but good nine volt battery might be in order.
You want to see smooth movements to open and close against the internal spring.
Your voltage should be higher under a rapid stop unless you have corroded connector pins.
You can just pull it off and on the connector while you are working on the accordion hose prior to check them for the giggles of it.
The nine instead of twelve slows the power down a bit so you can see if it drags.
The nine volt is just something I like to do, to mimic, it working under a startup condition. This is when the battery voltage is lower.
This should take care of air control issues.
Phil
|
