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Weak Idling Back Again - 3 Weeks After ThrottleBody Cleaning

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So it's been 3 weeks since I cleaned the Throttle Body on my car. The idling has been fine at cold startup since then...until now.

The weak idling at cold startup came back 2 days ago. The first time, it stalled right away, second try and it was fine.

Then yesterday, it started with a weak idle, the symptoms are just as before I cleaned the Throttle Body.

So I took everything off to check the Throttle Body again,

As expected, it was still clean. The only other thing I could see in there was a layer of clear yellowish film of oil

on the walls of the Plenum, and there was a tiny drop/drip of that too, collected on the bottom edge of the butterfly.

Looks like engine oil to me, but it was clean and clear yellowish.

I've read that it's normal to have a mist of oil on the insides of the Throttle Body and the Plenum, how much is normal?

I didn't see any puddles whatsoever, but a rather "heavy" mist/layer on the walls,

and of course the drop of drip on the bottom edge of the butterfly. Is that normal?

I am suspecting it could be an Air/Oil Separator going bad slowly,

or the piece of electronic gadget on the Throttle Body itself, that controls the idling and buttlefly.

Out of curiosity, I took apart the casing for the electronics on the Throttle Body to look inside...

nothing much but a few cogwheels and a small electronics board.

The car still drives well, it's just the cold start, but once the few seconds of weak idling catches on, it idles fine.

The Battery/Generator light does come on, but promptly goes away once the idling catches on.

This, like I mentioned before, could be due to the alternator not being able to start charging yet due to the weak idling.

Any ideas on what to do next? I just want to be prepared and start troubleshooting it now, instead of waiting to be stranded.


EDIT: Oh, I forgot to add that I've been getting some 'white smoke' startups lately.

Not much, but noticeably enough, even if I haven't been pushing the car the last time before I shut down.

The white smoke goes away after a few seconds though.

Edited by CosmosC4S
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Some shops have a gauge that replaces the oil filler cap - they use that to see the crankcase pressure. High crankcase pressure is usually a sure sign of AOS or bellows failure.

Sorry but I thought if the AOS failed it would have high vacuum in the crankcase not pressure. Loren am I out to lunch on this??

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Thanks Loren and wvicary.

So, I should start by having the crankcase tested for high vacuum, for a possible bad AOS.

If the AOS is fine, chances are that electronic thingie on the Throttle Body is starting to go bad?

Btw, is the layer of oil mist on the walls of the plenum normal? They look like clean engine oil to me.

What about that little drip of oil on the bottom edge of the butterfly?

OR...another possibility...since I am also having this early symptoms of a bad ignition switch,

is it possible that the bad ignition switch is affecting the proper functioning of the throttle butterfly at cold startup??

Sorry, I'm just wild guessing.... :unsure:

Edited by CosmosC4S
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  • 2 weeks later...

I am having similar problems with weak idling at startup. Once the oil is up to temperature upshifts result in a large puff of smoke and high oil consumption with smoke at first startup after tracking the car.

My carrera is an MY02 and thought the bellows were replaced after MY01.

Can someone explain why a leak in the AOS causes an increase in vacuum rather than a decrease?

Edited by RCasto
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