Rough idle at no load!!
#1
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Rough idle at no load!!
The engine is nice and smooth when cold, however as it worms up and the revs drop the engine settles into a rough and uneven idle. Switching the AC on makes the engine idle smoothly! Engine is smooth under load at all rpms.
The car was like this when I bought it a year ago, I have changed the sparks plugs, new air and fuel filter, added injector cleaner several time with no change. I have even tried spraying WD40 in the vacuum tube leading to the idle stabilizer with no improvement.
I have even disconnected the vacuum lines and plugged the connector on the intake manifold with no improvement.
What could be the problem?
Thanks, Azir.
The car was like this when I bought it a year ago, I have changed the sparks plugs, new air and fuel filter, added injector cleaner several time with no change. I have even tried spraying WD40 in the vacuum tube leading to the idle stabilizer with no improvement.
I have even disconnected the vacuum lines and plugged the connector on the intake manifold with no improvement.
What could be the problem?
Thanks, Azir.
#2
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Is your engine properly timed? Check spark advance as that has a really big impact on idle speed. It needs to be timed revved up and then checked at idle.
The Manual 24-1 reads, 750 +/- 50 rpm at idle, from mod 1983 650 +/- 50 rpm. The Manual 28-23 reads, 23 degrees before TDC at 3000 rpm with both vacuum hoses removed. Then it should settle around to 10 at idle speed.
The Manual 24-1 reads, 750 +/- 50 rpm at idle, from mod 1983 650 +/- 50 rpm. The Manual 28-23 reads, 23 degrees before TDC at 3000 rpm with both vacuum hoses removed. Then it should settle around to 10 at idle speed.
#4
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OK, I checked the timing, fully wormed up engine, 3000 rpm I read 25 Deg aprox. and at idle it is about 10 to 11 Deg. Please remember this is an 87 S4 with ECU!