Re: 5KCSTQ:runnability problems -update

[Pcarselle <pcarselle@worldnet.att.net>]

Randall Paquette wrote:
> 
> Folks,
> A bit of an update to my dreaded problem previously posted and described
> below.
> The temp sensor on top of the waterboss appears ok - reads about 60ohms when
> warm.  The o2 sensor is generating around .5 volts and fluctuating when warm
> and disconnected from the controller.  Duty cycles seem strange (I have never
> checked before so have no baseline to compare to).  Car cold start - dudty
> cycle about 50% and steady.  Engine warm at idle-fluctuating around 75%.
> Throttle up to 2000rpm and duty cyce drops to 30% and when returned to idle
> slowly creeps back to 75%.  Funny thing happens, though.  If I really give it
> some willy (4000rpm) and let up on the throttle, car may not return to idle
> good at all (will then continuously stumble until restart with duty cycle
> around 50%).  If I remove the sensor connector at the top of the water boss,
> the car immediatley stalls, then in virtually impossible to restart (with
> connector re-attached).  My initial guess is that I'm running rich, AND that
> when the rpms go high enough, the car enters some further version of closed
> loop control and some sensor is causing a prollem.  Hope this helps some of
> you gurus with some ideas....  BTW, what size allen wrench do I need to
> fabricate to adjust the fuel dist?
> ----------------
> I'm having a problem with my 86 5KCSTQ (168,000miles).  Its a rough idle,
> stumbling problem that has progressivly gotten worse over the past few weeks.
> I'll describe the symptomology, relate what I've done, and exporess my plans
> if noone has any suggestions.
> It starts hard.  Only starts easy if its been less than 10 minutes or longer
> than 4 days.  In those circumstances, it fires right up.  Otherwise crancks
> for 20 seconds or so.  Lately, though, the idle has started dropping,
> requiring me to blip the throttle to keep from stalling - if stalled, have to
> pull off the road and it can take 10 minutes to pry it back to life.  It
> sometimes idles ok, sometimes won't hold the idle.  Sometimes develops full
> boost and sometimes stumbles.  It also seems to be running rich, smells rich
> and during my recent examinations, has spewed gas out the tail pipe on the
> driveway.
> What I've done:  ran the diagnostics, no problems detected and all things that
> are supposed to run (valves, fuel pump, etc) do.  Used the dreaded propane
> vacuum leak test - to no avail.  Idle stabilizer cleaned and tested.  Throttle
> idle/full throttle switch tested.  Recent new OXS installed.
> What I'm planning on doing: Remove cat converter - if plugged, what can I use
> to coerce the inards to break up and fall out?  I'd like to adjust the
> mixture.  I don't have a long enough 3mm tool to reach (any suggestions?) nor
> do I have a duty cycle meter (have old dwell meter if that helps).
> As I live over 100 miles from a dealership, any help would be greatly
> appreciated!!!!!  Please reply direct to me as I'm still using temporart
> e-mail accounts.  Thank you all.
> Regards,
> Randy Paquette
> QPILOT@NETSCAPE.NET
> 
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Randall:
I don't know if you have done this:
Replace fuel filter
Check fuel system volume NOT just pressure !!!
Sounds like a "lean" condition....and lack of overall
system pressure...suspect partially clogged strainer at fuel pump...
Check Scott Mockry's web page for very good info