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mkc2bad

Replaced AOS, but idling rough

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Hello Everyone!

My car was making the belt squeaky sound very loudly, removing the oil filler cap elimited the noise. I therefore thought the AOS was failing (in part it may have been) I replaced the AOS after following the excellent guide as linked on from this forum - However the squaking noise is still just about audible (much much fainter) The car is also idling very roughly anytime you come off the throttle. It tends to sort itself out after 5 seconds or so but I can tell something isn't quite right - feels slightly more brash and lumpy, rather than the silky smooth feeling it had before. It also caused the check engine light to come on - I've since reset the battery as I took the AOS out and re connected it all fearing I had not connected something correctly. I'm 100% sure everything is now connected properly. I was given a new rubber hose bit with the AOS (is this the bellows??) that connects right at the bottom of the AOS. I replaced the spring type clamp with a jubilee (screw) type clamp.

Any ideas as to where the problem maybe? Would it be worth replacing the plastic Y tube that connects the AOS to the throttle body? At a guess I'm assuming there is a vaccum leak somewhere as when I take the oil filler cap off the car idles much more smoothly.

Thanks

Mike

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Hello Everyone!

My car was making the belt squeaky sound very loudly, removing the oil filler cap elimited the noise. I therefore thought the AOS was failing (in part it may have been) I replaced the AOS after following the excellent guide as linked on from this forum - However the squaking noise is still just about audible (much much fainter) The car is also idling very roughly anytime you come off the throttle. It tends to sort itself out after 5 seconds or so but I can tell something isn't quite right - feels slightly more brash and lumpy, rather than the silky smooth feeling it had before. It also caused the check engine light to come on - I've since reset the battery as I took the AOS out and re connected it all fearing I had not connected something correctly. I'm 100% sure everything is now connected properly. I was given a new rubber hose bit with the AOS (is this the bellows??) that connects right at the bottom of the AOS. I replaced the spring type clamp with a jubilee (screw) type clamp.

Any ideas as to where the problem maybe? Would it be worth replacing the plastic Y tube that connects the AOS to the throttle body? At a guess I'm assuming there is a vaccum leak somewhere as when I take the oil filler cap off the car idles much more smoothly.

Thanks

Mike

Sounds like you may have accidentaly pulled the small vacuum line off the intake plenum or the reservoir , It is located right next to the AOS (small plastic tube) there is a y fitting in the vicinity too, but they are delicate and easily pulled out. check you pet catalogue illustraion 108-05

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Hello Everyone!

My car was making the belt squeaky sound very loudly, removing the oil filler cap elimited the noise. I therefore thought the AOS was failing (in part it may have been) I replaced the AOS after following the excellent guide as linked on from this forum - However the squaking noise is still just about audible (much much fainter) The car is also idling very roughly anytime you come off the throttle. It tends to sort itself out after 5 seconds or so but I can tell something isn't quite right - feels slightly more brash and lumpy, rather than the silky smooth feeling it had before. It also caused the check engine light to come on - I've since reset the battery as I took the AOS out and re connected it all fearing I had not connected something correctly. I'm 100% sure everything is now connected properly. I was given a new rubber hose bit with the AOS (is this the bellows??) that connects right at the bottom of the AOS. I replaced the spring type clamp with a jubilee (screw) type clamp.

Any ideas as to where the problem maybe? Would it be worth replacing the plastic Y tube that connects the AOS to the throttle body? At a guess I'm assuming there is a vaccum leak somewhere as when I take the oil filler cap off the car idles much more smoothly.

Thanks

Mike

Mike:

The little accordion-type "rubber hose bit" is the bellows.

Double check all of the mechanical connections on both sides of the bellows, and at both ends of the plastic "Y" tube. Also make sure that the AOS is firmly seated against the side of the engine where it is held secure by the two 10mm bolts.

Check the connection between the two parts of the oil fill tube (from the bulkhead section to the middle hose) as it may have been disturbed during the AOS install.

Regards, Maurice.

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Thanks for the replies guys.

Ok I double checked that all the connections were in and they are all tight and clipped in properly. I can see all the other tubes for the air system with the Y peice etc, and they haven't been disturbed and again, are connected ok. I reset the battery again, and for the first few minutes while the car is cold it appears to be ok, but as soon as it warms up the rough idling starts again and the revs sometimes really dips and almost stalls the engine (but not quite). I can also still hear a very faint belt squeaking noise, but only once it is wamred up.......I toook the car to a local garage, and they kindly hooked their diagnostic tool up - the fault is coming back as the o2 sensor being faulty. Would this be the case (ie can a failing o2 sensor give the problems i'm having?) or would a vacuum leak also cause it to throw this error? I keep thinking it is a leak somewhere, mainly duue to the fact that the squeaking is still there........

Thanks

Mike

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This is just a guess but maybe your oil fill tube was already old and working around it may have damaged the accordian section near the rear buckhead. You could try wiggling it with the engine running to see if you can hear anything or notice the motor changing its rpm. Or you could spray some flamable solvent (carefully - fire extinguisher on hand) on the fittings around the area to see if the motor picks up speed to pinpoint a vaccum leak. Some garages have a special smoke testing machine to locate leaks.

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I second the checking of the oil filler tube. I ended up having a huge vacuum leak in mine. However, my leak was so big that it had gone beyond squeaking and was causing a high idle. Small cracks can be patched with epoxy.

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Thanks again for all the suggestions. I ended up taking it a garage. He checked for leaks - none. The ecu was reporting no reading on one of the o2 sensors. Had this replaced and it's all running fine now :)

cheers

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