Re: mechanics stumped

[DeWitt Harrison <de@aztek-eng.com>]

On Thu, 11 Sep 1997 10:36:06 +0000, Greg Woodard wrote:
>[ ... ]
>1987 1.8 4cyl.
>
>My son can start the car in the morning and drive it to school (15 
>miles)- no problem.  Start it after school and and drive it to work 
>(15 miles)- no problem.  Start it 2 hours later and drive it home- no 
>problem.
>
>But if he drives around town, stop and go driving, lets it idle for a 
>few minutes.  It will start to miss.  He can limp it home, but it 
>takes over 1/8 of a tank of gas (14miles).   You can smell raw gas 
>almost running out of the exhaust.  The plugs will be completely 
>black.  If we clean the plugs and leave it sit overnight, he can 
>drive to school- no problem.  
>
>We have replaced nearly everything with known good (ie borrowed from 
>my 1.8).  I'm stumped, my sons stumped and several mechanics are 
>stumped. [ ... ]

If this turned out to be a carbureted engine, I would say the carb bowl
float sinks allowing the bowl valve to open and route full fuel
pressure to the jets. This would override the fuel metering function
of the carburetor. If it's FI, the same principle would hold; part of
the fuel distribution system goes belly up, e.g. the fuel distributor
sticks when hot. Around town driving may produce higher under-
hood temperatures than cruising.

DeWitt Harrison   de@aztek-eng.com
Boulder, CO
88 5kcstq