re: Oscillating tacho on 75 TS

[David Masters <david@xxxxxxxxxxxxxxxx>]

[]  JH Tay asks ....

My tachometer (and engine) has recently developed this problem of
oscillating (sometimes between 800-1000rpm and sometimes down to
700-1000rpm and stalling the car) when the car is stationary. This happens
almost after I start off the car as after driving for a while (and then
stopping the car), persisting anytime from tens of seconds to a few minutes
before it goes away.

I have replaced the air-flow meter unit (which includes the chip) with
another 75 TS's. The problem persists, however. Does anyone have any advice
on this? Could it be due to clogged fuel injectors?
[]
Yes, it could be clogged fuel injectors, use Techron or Caltex Injector 
cleaner regularly.  However, it is more likely to be just general ALFA 
maintenance items.

Pay particular attention to cleaning the idle speed stabiliser, and the 4 
wire plug behind the cardboard behind the throttle butterfly.

I posted this a while ago...
Fool Injection 101.

Clean everything first!
I am heartened to see that everyone isn't advocating the total replacement 
of all components including the ECU, so that is great.

Try this:
Clean the battery terminals, that is good for 5 HP
Clean all the earths on the engine and grill brace
Clean all the Bosch connectors (AFM, TPS, Idle Stabliser, temp sensors, 
etc)
Clean the connector to the computer
Clean the 4 relays in the engine bay

Then, recently I have added these steps:
disassemble the intake to the butterfly,
Use contact cleaner or equivalent to wash out the flap are of the AFM, and 
the Idle stabiliser, (the round thing on the RHS of the plenum).  Clean the 
intake tract, and around the butterfly.
Remove and clean the vapour separator. (Fill it up and soak it in kero or 
something similar.)

That ought to do it!

For extra credits you can connect a DVM to the output from the O2 sensor 
and check your voltage oscillates, but they tend not to be a problem.

YMMV, etc.

Cheers,
David Masters
1989 ALFA75 TS.  130000kms.
Newcastle AUSTRALIA.

Many thanks in advance.

J H Tay
'90 75 TS

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