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AOS? slight rough idle cause?

GranburyChuck
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GranburyChuck Member

GranburyChuck

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Okay, I have been reading the posts about the AOS and am a little confused. I have a 2000 C2 tip and was looking for the source of a possible vacuum leak. Decided to take the oil filler cap off and found some significant suction. Also, the car idle became a little rough. Reading posts suggests there should be anywhere from no vacuum to a slight vacuum (not sure how slight "slight" is). I do notice some oil accumulation on the outside of the intake plenum on the drivers side. Also, I have cleaned the throttle body and it was fairly dirty and could see some oily residue inside the plenum. I don't really notice smoke on start up except when it is very cold out (thought that was condensation). Is there a good and correct way to test the AOS?

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RFM Member

RFM

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Remove the black plastic AOS tube from the throttle body, plug up the hole in the throttle body, let the engine idling. If the engine idling smoothly like it's should now, be sure the fault is in the AOS or bellows.

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RFM Member

RFM

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Black plastic tube, diameter approx. 2 cm, left side behind the throttle body. Plug up the open hole and let the tube ganging freely in the engine room. The tube is the vacuum line from the manifold to the AOS, the AOS is inactive with the tube removed. If the engine idle normal in this condition and the DME actual values returns to normal, the AOS is faulty (vacuum loss = air leak)

JeTexas Member

JeTexas

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Black plastic tube, diameter approx. 2 cm, left side behind the throttle body. Plug up the open hole and let the tube ganging freely in the engine room. The tube is the vacuum line from the manifold to the AOS, the AOS is inactive with the tube removed. If the engine idle normal in this condition and the DME actual values returns to normal, the AOS is faulty (vacuum loss = air leak)

Can you actually drive the car with the hose removed to test it or should you only let it idle?

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RFM Member

RFM

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Just at idle is recommended, the engine room can be sprayed with oil and smoke coming from the removed AOS tube.

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