Engines Surges

**Air Force One** · 11-12-2009, 02:19 PM

1990 Chevy 1500. Auto 305 V8. Engines surges...revs up high/low ...up/down...TPS, and just about every others componet has been replaced....Brakes are a little spongy...will having a Vacuum leak in the engine area affect the brakes??? Advise greatly appreciated...

**dsfloyd** · 11-12-2009, 02:28 PM

I would definately check for a vacuum leak for the surging.

**Air Force One** · 11-12-2009, 02:54 PM

When checking for a Vacuum leak...whats the best way? Using Carb cleaner and spraying around the hoses listnening to engine racing up?? Advise? Thanks!

**dsfloyd** · 11-12-2009, 05:31 PM

Using carb cleaner is on way to do it. Make sure there is no open flame or spark first

(always need warnings right?). with the engine idling spray along hose and fittings. If there is a leak the idle should briefly pickup then drop again. They can be very hard to find sometimes. A smoke test is another way but is done at a shop. Not sure of cost.

**Pizzot** · 11-30-2009, 04:44 PM

If its while you are not moving, in neutral, parked, or any other time the truck is at idle and your getting the hi rev low rev its definitely the Idle Control Valve. I replaced mine and problem stopped.

**k.daddy1** · 11-30-2009, 05:11 PM

Originally Posted by Air Force One

When checking for a Vacuum leak...whats the best way? Using Carb cleaner and spraying around the hoses listnening to engine racing up?? Advise? Thanks!

Spray around the base of the T/B. I've replaced a lot of the gaskets under the throttle body for the same defect your describing. Vaccuum leak will also cause it too. Good Luck!