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Re: mysterious fuel problems
My friends 85 5KS had the similar symptoms of : low mileage and fuel
after much troubleshooting it turned out to be a cold start valve problem,
the purpose of the cold start valve is to richen the mixture at start time
only depending on temp, etc....
his was leaking fuel into the engine compartment (drop by drop) and also
seemed to fire for longer than needed at startup, the time that the cold
start valve fire is determined by a thermo time switch on most Bosch fuel
injection systems of your vintage if the thermo time switch is firing too
long (hard starting might happen) after replacing the actual cold start valve
and associated seals it improved his mileage by 4 mpg in normal day to day
When I installed the P-FLO filter kit on my 86 GLI 8V, I remember reading
warnings about the air flow plate and if the resting position adjustment was
not precise, the result would be rough idle, decreased mpg's. (nothing about
The Haynes, Clinton, and Bentley manuals I have on fuel injection systems
seem to agree on the following troubleshooting if poor mpg is seen or fuel is
smelled . . . .
- dirty or faulty air element .......
- incorrect timing ..... I believe you checked this already
- emissions related equipment not functioning properly
- injectors worn or clogged . . . you mentioned as a possibility
- missing @ RPM somtimes points at the wiring harness, vacuum etc.....
remember that the fuel injectors are the end of the fuel system.... the
metering portion of the fuel injection system should be checked as well.....
just my $ .02 worth.
Do you think that all the fuel lines and fuel return lines are fully intact,
some of these need to be inspected with the car elavated in order to get a
good look at all of them.
I do not know if that is your problem, just providing some info which may
apply. Sorry about length of message.
Family Audi's 93 S4, 87 5KCSTQ, 85 5KS, 90 100.