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Changed Oil & Filter; Now Idle messed up

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Hi, All;


2001 C2, 6 spd


First off, I know how to change oil. Have done it several times on my 996 with no ill effects.


On Tuesday, I changed the oil and filter after backing the car onto Rhino Ramps.  All went well.  Filled the crankcase with about 7 qts (didn't want to overfill), started the engine, and drove it off the ramps. Shut 'er down.  Checked oil level; added a bit, then went for a test-drive. When I came to the first stopsign, it was running quite rough, like it was loading up.  Turned around, keeping the revs above normal idle speed.


Got home, and made sure my wife had her phone with her, just in case.


Took it out again, and the "loading-up" wasn't there.  However, when I came to a stoplight (i.e., more than 5 seconds at idle), the idle went from its normally rock-steady state up to about 1200 rpms. It would drop down if I blipped the throttle, but then at the next light (and every one since then) it starts to inch up until I blip it.


I didn't pull on anything, no codes are present, I didn't even bump anything.  Car has been rock solid for over 2 years.


Any ideas?

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Check if the oil cap is tight and if there are any cracks on the oil filler tube. Sounds like vacuum leak.

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Thanks, Ahsai & Loren;  makes perfect sense now that I think about it.  I did release the oil fill tube from the clamp in order to not spill the new oil, but the tube has always been pliable.  Still, after almost 17 years....


re: the o-ring in the oil filler cap, I'll have to check that, too. When reinstalling, it seemed not loose, but not snug, either. Still, found no spare parts on the ground (!).


At least I have something to go on now!

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I replaced my oil filler tube a few years back when the car was about 10 years old.

Edited by Hilux2400

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Well, you guys are great!  Went out this AM; moved the filler tube around; really couldn't see if there were any gaps in the accordion folds, etc, and didn't hear any cracking sounds.  I know plastic is more age susceptible, but the car only has 51,000 on it, so fewer heat/cool cycles than an average 2001.


Then I checked the filler cap. Didn't seem loose, but I rotated it 90 deg and re-installed. Definitely felt "snugger."


Took it for a 45 min drive, and not once did it exhibit any idle or operational issues.


Thanks again!!  I *knew* these vehicles were crankcase pressure sensitive, but it just didn't pop out of the gray matter when it surprised me with erratic operation.


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