Rough idle

[tjbabar]

I have a 1984 944 that idles rough. The engine mounts are new, the
timing belt is tight, the compression is good in all cylinders, the
balance shafts are set correctly. I am suspecting the fuel
injection. What component of the fuel injection would cause rough
idling and how can I test it?

[Bill Noble]

1. why do you suspect injection - my first suspicion (based on a half a
dozen 944s I keep happy) is ignition wires and cap - are you positive they
are good?

2. I've seen balance shafts set wrong a lot - could be worth double or
triple checking

3. the air flow sensor wears out near the low RPM portion and can cause a
distinct dead band

I have seen injectors clog, this was on an 84 that sat for about 10 years
undriven and filled up with mice droppings and snail shells (the mice ate
the snails) - A young lady bought the car from a friend for $500 and we got
it running in a day or so - drained the mouse urine out of the air cleaner,
took injectors off and cleaned them with carb cleaner (you can actuate them
manually to get the solvent to flow through), put it all back together,
added a battery and it started right up. (it took some more work to be
safe to drive, mind you)

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