Engine Surges & Stalls...

[Mark B]

Hey everyone,
I have two problems that I think may be connected.

-If I am crusing down the highway for a while & put the clutch in to downshift for an offramp... The engine stalls. (Will only happen 25% of the time.)

-While sitting at idle, the engine will continuously surge up & down.(100% of the time.) Sometimes the RPM's will get pretty low/

Im wondering if the surging is causing the stalling? Any thoughts what could be causing this? IAC?

[TraceZ]

Could be EGR related? IAC?

[BmXRacR96]

To me it sounds like it could be a vacuum leak. Check for leaks on major lines, IE PCV, Brake booster and intake manifold. Also check Fuel presure regulator for leaking fuel on the vacuum hose(remove the vacuum hose to check). If it has a MAF, tap on the housing and see if rpms change or engine stumbles. If it does, try a different MAF. If not it should be OK. and check air intake hose from MAF to Throttle Body.

If thats all good its prob the IAC

Doug

[TraceZ]

IIRC, his car is throttle body injection, so no MAF sensor. Checking all the vacuum hoses is a good place to start. get a can of starting fluid and spray the vacuum lines and conectors. You'll know you found a leak when the RPMs increase due to starting fluid getting in the system.

If it were me, I'd take the throttle body off and give it a good tear down and cleaning in addition to checking for vacuum leaks.