Re: '87 TQW idle problem?

[steveb@newkla.kla.com (Steven Buchholz)]

>   very well otherwise. I checked the idle stabilization solenoid, it
>   appears to
>   be working OK and is clean. The problem persists exactly as before if
>   the idle stabilizer is disconnected. Opening the oil filler cap
>   immediately
>   stalls the engine. No obvious holes/tears in turbo induction hoses.
>   The 900 RPM-to-2KRP-back-to-900 RPM cycle takes about 3 seconds.
>   A/C on or off makes no difference.
> 
I wouldn't expect a leak to the atmosphere because that would screw up the 
mixture and make it difficult to run at all.  It sounds like the problem is 
that intake air is getting around the throttle body somehow ... you checked 
the idle stabilization solenoid to no effect.  I was surprised to hear that 
disconnecting the solenoid made no difference ... my '88 nearly dies when 
the solenoid is disconnected.  You also said that the symptom is the same 
independent of the A/C ... try pinching off the lines to the A/C air bypass 
solenoid to see if that doesn't help.  The only other thing that comes to 
mind is the idle speed adjustment screw on the throttle body itself.  Has it 
come loose or fallen out completely?  Other than that I would look at all of 
the connections on the intake manifold side of the throttle body (including 
the vacuum lines that come off the back of the manifold) and test by pinch-
ing off any hoses.  

I don't think that a fuel system problem would cause the symptoms that you're 
seeing.  If the air metering plate was not returning properly or the control 
pressure regulator was malfunctioning it would simply screw up the mixture ... 
no more air would be allowed into the engine.  

Best of luck on your quest!
Steve Buchholz
s_buchho@kla.com