re. 5kcstq engine problem when cold

[Colin Hames]

Possibly a sticky or failing Idle Stablizer or Decel Valve.  I  would bet the
ISV.  Try unplugging it and see if the running condition is similiar to your
intermittent symptoms.

Colin


Swann, Benjamin R. (BSWANN) wrote:

> I may be haveing the same or similar problem.  Engine slightly warm, cold
> outside ~ 30-45F.
>
> Upon letting off the gas, the engine drops to about 300 RPM, like it is
> going to stall, then recovers.
>
> I had corrected a fast idle/poor fuel mileage problem about 2 months ago
> caused by the throttle adjust screw vibrating/backing itself out.  Put some
> of my favorite black goo - aviation gasket seal, and seated the screw all
> the way closed.
>
> Then the car was running and idleing perfectly until about a week ago.
>
> The problem is as you describe, intermittant.  I  check my vac. lines about
> every month, almost all have been replaced and everything is kept tight.
>
> Most vac leaks I've dealt with cause the car to idle fast.  Where would the
> opposite occur?
>
> <On two occasions, I've had a engine problem in my 5kcstq: the engine
> idles extremely low or tries to die. It might idle at 400 rpm,
> increasing a little as the engine warms up. It's not only an idle
> problem, though. While driving, if I lift my foot, the deceleration in
> gear is more sudden than usual and the stock boost gauge (I know,
> inaccurate) read 0.0 bar. (It usually reads 0.2 bar or so near sea level
> when decelerating in gear.)
>
> This happened on two chilly evenings, a few weeks apart, but hasn't
> happened otherwise.
>
> I would think it was a vacuum leak except for the deceleration behavior;
> my previous experience with vacuum leaks has been that you only notice
> them at idle. The intermittent nature of the problem makes it hard to
> diagnose, too. Any suggestions?
>
> - Wallace
>   '87 5kcstq 167k>