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'89 200TQ intermittant no-start/running like hell solved
I had recently finished the top end engine work on the 200 engine. Upon
completion she started up easily and ran fine for an hour. Shut it off.
The very next morning she quit on me, then barely started, ran like
hell, stalled again and it was over. Of course, no codes on display.
Naturally, I started to blame usual CIS vises: vacuum hoses that I might
have forgotten to connect, the electrical connectors which forgot to
plug in and all other kinds of similar goof-ups which are pretty common
bugs one has to eliminate after a major engine work, especially
exacerbated by the fact that the whole month elapsed between
disassembling and assembling the car.
Over the years that I dealt with Audis I got used to a typical CIS
scenario: no vacuum => no fuel => no run, that it took me several hours
of tearing apart and plugging various hoses (my favourite "How to catch
a lion in a desert" technique) before I finally realised that this is
not the CIS issue.
Pulled my inductive High Tension LED indicator and asked the wife to
crank the engine. Bright glow at the central (coil) wire, no glow at the
spark plugs. No spark! Gotta be the Hall sender, of course. Jeez, what a
rocket scientist! Took me 3 hours to figure out the obvious.
The plug for the Hall Sender connector has been broken off and hanging
loose for 3 years now. Took the distributor out of the car. The
insulation on two out of three wires for Hall Sender (GRN and RED) had
been worn to the bare strands. These exposed strands had been touching
on and off the rotating metal cylinder for Hall Sender, i.e. it's been
intermittently grounding the signal wire for the Hall Sender.
Pulled all 3 wires out or the plastic housing, sleeved them with 1/8"
heat shrink tubing, put them back into the housing.
Strapped the broken housing to the body of the distributor with a wire
tie. The car started from a quarter-turn. End of story.
Check your distributors! I guarantee that 9 out of 10 older Audis out
there have the plastic housings for the Hall Sender broken off the
'89 200TQ -- 18psi (TAP)
'98 A4TQ -- nothing to declare