3.2 Coast down stalling

[Botman]

Hello all,

I'm looking for some direction with an interesting problem I have with my 86 3.2 Carrera. When slowing down, if I push in the clutch with the revs over 1500 and throttle closed, the engine will keep on idling down until it dies. The problem is most noticable under heavy braking. The revs will very often dip down to 400 or so and then "bounce" back up to the normal 800 if it does not stall. I have been getting around the problem by using engine braking and not pushing in the clutch until I am almost stopped and the idle has dropped to under 1200 rpm or so.

Although the car has 232,000 miles on it!!!!, a complete rebuild was done 34,000 miles ago and I have vg compression. The car runs very strong except for this problem.

Any help or direction is appreciated,
BotMan in Houston

[ChrisBennet]

From my own limited experience this is what I would try:

Your idle stabilizer valve (ISV) may be "walking towards the light". The ISV is a valve that is opened and closed in duty cycle fashion by a little motor. Its sits right in front of the throttle body and lets air around the closed throttle so the engine gets enough air to idle. The contacts for the ISV motor eventually wear out but sometimes the valve is just gummed up. Try spraying some carb cleaner through it. You should be able to feel the motor buzzing when it is running at idle.
Another possibility is that the "off idle" microswitch on the throttle lever is not working. With the motor off, pull on the throttle lever and listen for a faint "click" as soon as the lever moves. The switch lets the computer know that the engine is at idle - and that the ISV should let air around the throttle plate.

Hopefully the real "brains" on this board will be more helpful.
-Chris

[Botman]

I was hoping that it would be something like this, and not some "gremlin". Thank you, Chris for giving me a starting point!

Botman

[Joeaksa]

Botman,

Find someone else with a DME car and swap out the idle valve and see if it follows the valve. Just did it with another pelicanhead here in town and it takes 10 minutes to switch out. You can tell if the valve is bad without spending $130 first.

Joe

[89911]

Make sure all your vacum hoses are in place leading to the throttle body and air box.

[BKOMAR]

Does CIS have an ISV? because my 80SC does the same thing , esp. when warmed up. It will bounce and continue bouncing until I manually stabilize it with the gas pedal. If I slow down and keep the car in gear down to ~1000 RPMs and release the clutch, it stabilizes fine and doesnt bounce. I can tell even when switching gears that the RPMs go well below idle between shifts... and bounces back up when the gear is engaged and clutch released. I have wondered if this is good for the motor? Brian