Stumbling at high boost... advice needed

[Doyt W. Echelberger]

I also have an 87 5ktq and the two major causes of stumbling in the past 
three years have been a faulty WOT switch and a failing oxygen sensor.  If 
you haven't already replaced your WOT switch in the life of the car, just 
do it on general principles. SMJ found every one of the WOT switches he 
tested on these cars to have at least one fractured electrical connection 
inside the switch.

My oxygen sensor slowly failed over about 6 months time, and gradually the 
stumbling and stalling increased during this time.  Get a new one if yours 
is over 30,000 miles old.

Of course, you must touch and feel and roll between your fingers all the 
vacuum hoses, searching for hard spots and soft spots. Especially the big 
crankcase vent hose that comes out of the engine on the US driver side and 
goes up across the valve cover, where it has some connections that 
frequently get loose. And also, take out your supply tank for the 
windscreen washer, and check the short vacuum hose that runs from the 
wastegate to the intake manifold. It is about 6 inches long and fabric 
covered, with thick walls.  On my car, it had hardened and crumbled and the 
crumbs had been sucked into the manifold, leaving only the hollow fabric 
cover (which constituted an enormous vacuum leak.) Pinch it with your 
fingers all along its length to be sure it is OK.

That's my best advice.      Doyt Echelberger

 >>>>>>>>>>>>>>>>>>>>>>>>>>.
At 07:00 AM 8/25/2000 -0400, you wrote:
Hi gang...

Having some slight stumbling on my 87 5ktq.  It has been chipped and has the
1.8 bar spring. .......snip.........................................
any suggestions on what you might think the MOST probable reason for this
is... its not affecting drivabilty for the most part, just kind of annoying