warm start/idle stall, deceleration stall

mrrichard · 08-12-2003, 09:55 PM

Stock '87 GT convertible. 140K miles.

With engine warm, occasional stall when clutch disengaged and deceleration.

Also, at warm start, rpm surges up, back down to stall. Re-start, gun it up to 2000 rpm for 15-20 seconds, let up, and idle stabilizes fine (until next stop sign perhaps!).

Acceleration and cruise are fine. Idle is okay. IAP valve seems to operate fine and ports are clean. New EGR and solenoid, and EGR ports are clean. Throttle clean. New fuel filter. New PCV valve. No obvious vacuum leaks or blocks. New plugs, wires, rotor, cap. Injector cleaner run through gas tank.

Only fault codes kicked out are thermactor air management system (smog pump and plumbing), left and right side(81,82,44,94). Smog blower is good, but air bypass valve (or solenoid) is known to be bad.

Can the air management circuit failure cause this stalling condition at warm start/idle or deceleration? Or must I look elsewhere -- TPS, O2? TPS voltage (green wire to ground) ignition on/engine off/closed throttle, is about .8V max.

Any ideas for this pesky problem? Since reving it up seems to stabilize the idle, I wonder if it's exhauast-heat related? Don't know much about fuel pressure, but should I check that? Any help would be appreciated.

Thanks.

08-12-2003, 09:55 PM	#1
mrrichard Registered Member Join Date: Aug 2003 Posts: 2	warm start/idle stall, deceleration stall Stock '87 GT convertible. 140K miles. With engine warm, occasional stall when clutch disengaged and deceleration. Also, at warm start, rpm surges up, back down to stall. Re-start, gun it up to 2000 rpm for 15-20 seconds, let up, and idle stabilizes fine (until next stop sign perhaps!). Acceleration and cruise are fine. Idle is okay. IAP valve seems to operate fine and ports are clean. New EGR and solenoid, and EGR ports are clean. Throttle clean. New fuel filter. New PCV valve. No obvious vacuum leaks or blocks. New plugs, wires, rotor, cap. Injector cleaner run through gas tank. Only fault codes kicked out are thermactor air management system (smog pump and plumbing), left and right side(81,82,44,94). Smog blower is good, but air bypass valve (or solenoid) is known to be bad. Can the air management circuit failure cause this stalling condition at warm start/idle or deceleration? Or must I look elsewhere -- TPS, O2? TPS voltage (green wire to ground) ignition on/engine off/closed throttle, is about .8V max. Any ideas for this pesky problem? Since reving it up seems to stabilize the idle, I wonder if it's exhauast-heat related? Don't know much about fuel pressure, but should I check that? Any help would be appreciated. Thanks.