88 5kq - Intermittant Hard Starting

[Huw Powell]

> 88 5kq - no turbo - NF engine
> Symptom: Intermittant Hard Starting under cold and hot conditions.
> Majority of the time, the car starts up fine . .cold or hot.

> I'm suspecting the MFS temperature sensor, thats the bottom sender between
> spark plugs 1 and 2. The MFS sensor feeds the CIS control unit so that it
> can adjust the Differential Fuel pressure Regulator(DFR) for proper fuel
> mixture. Either the electrical connection is not tight, or the CIS half of
> this sender is intermittant resulting in a lean mix for starting.

I think the MFTS only runs the temp gauge and feeds info to the AC 
system - the top, two pin black bodied sender is for the CISE3 warm up 
control (and ignition, too).

Anyway, there are a number of parts you can test one way or another to 
make sure they are working properly - or, at least, intermittently 
"good" when you test them!

NTC temp sender (top one) - each terminal, resistance to ground should 
be around 500 ohms cold, drops to about 70 when hot, even lower at, say 
boiling.

Resistance (open/closed) of idle and wot switches.

Resistance (should be about 16-22 ohms) of control pressure reg. (DFR)

Cleanliness of fuel path through DFR.

Air leaks anywhere... can be hidden.

Cleanliness, function of ISV.

Spark quality - wire resistance, plug quality, cap-rotor age, hall 
sender problems.

Grounds to intake manifold & all other electrical connections.

Ignition switch intermittence in "run" position...

There is more, but only maybe a dozen things to check all together.

-- 
Huw Powell

http://www.humanspeakers.com/audi

http://www.humanthoughts.org/