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Old 11-20-2015, 05:10 PM   #1
twitchyboy
 
Drives: 08 Yaris Sedan 5spd
Join Date: Nov 2015
Location: Kansas City, Missouri
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Erratic/High Idle

Hey Everyone,

The Problem 08 Toyota Yaris Sedan 5 Speed has erratic idle between 500 and 1000 rpms with it idling as high as 1500 when cold.

The Story

I recently purchased a 2008 Toyota Yaris 5 speed Sedan at ~82000 miles. The car drove great for about the first 1000 miles and idled at 500rpm. Before buying I took it into the toyota dealership and had them do a full inspection and they said it was in great shape - just would need recommended maintenance soon (replace spark plugs, change transmission fluid). I declined this, taking it to my local mechanic for a better price, but he couldn't fit me in.

So...because I travel for work, I took it on a 14 hour/900+ mile trip going 80-85 most of the way, the idle became erratic, ranging between 500 and 750rpm. Additionally, when the idle would range back down to 500, it would idle pretty rough, feeling like it was going to stall out.

After the 900+ mile return trip, the maint reqd light came on at ~84000 miles and I got the oil changed. I realize this is separate from the check engine light - just thought I'd add it.

After taking a ~750 mile trip going 85 most of the way, I noticed that the idle had started to range between 500 and 1000rpms. When the engine saw it's first really cold weather of the year last night (30s fahrenheit/0 celsius), it woke up and idled at ~1500.

After the car and the weather warmed up out in new mexico today (60s Fahrenheit/17 celsius), the idle continued to range between 500-1000rpm.

Other possibly relevant information:
1) previous owner drove it on a lot of gravel roads - could the extra dirt from this be clogging up the intake manifold or something?
2) Took it to autozone to scan for codes and they hadn't turned up anything

Next Steps?

What should I do here guys? Is there anything I can check on my own before I take it into the toyota dealership?
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Old 11-20-2015, 06:00 PM   #2
tmontague
 
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1500rpm is normal for cold start up.

The erratic idle is likely due to a vacuum leak and/or a dirty throttle body. That being said i'd put my money on a vacuum leak. With a decent code reader you can diagnose the vacuum leak by looking at fuel trims.

I can't think of anything else at the moment but i'd look into a vacuum leak.
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Old 11-21-2015, 08:08 AM   #3
bairjo
 

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Mass Air Flow sensor might need cleaned.

https://www.youtube.com/watch?v=5d2LonVb7_Q
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Old 11-21-2015, 09:28 AM   #4
Rigaud
 
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Quote:
Originally Posted by bairjo View Post
Mass Air Flow sensor might need cleaned.

https://www.youtube.com/watch?v=5d2LonVb7_Q
This.............plus throttle body, then verify for a cracked vacuum line as mentioned above
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Old 11-21-2015, 12:11 PM   #5
twitchyboy
 
Drives: 08 Yaris Sedan 5spd
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Guys! Girls!

I think I fixed it! Bought a $10 can of MAF cleaner at autozone, borrowed a screwdriver, and cleaned that thing out. The MAF didn't actually look that dirty from what I can tell, and I also took a look at the IAC while I was in there, which also looked pretty clean (again, from a novice perspective). I sprayed the MAF wires/metal (inside and out) with MAF cleaner, waited 30 minutes for it to dry, and then put it back in.

I started my engine up which was cool by that time at about 1500rpm, then it quickly went down to 1000rpm, then it hovered at ~750 rpm and slowly came down to just above 500rpm as I revved the engine and warmed it up.

Furthermore, the idle has stopped hopping up to 750 and is holding constant at just above 500rpm. I am going to wait to take it on another extended interstate drive at 85mph and then report back. For now I'm cautiously optimistic.

Thank you guys!
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Old 11-21-2015, 12:16 PM   #6
Rigaud
 
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Old 11-21-2015, 04:58 PM   #7
twitchyboy
 
Drives: 08 Yaris Sedan 5spd
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I celebrated too soon. When I took out and cleaned the MAF, it stopped the erratic idle until I took it on the interstate for 15 minutes at 3500rpms. Then it started idling between 500-750 again.

Sooo, I took out the throttle body and looked to see if the IAC was detachable. It was not. So I cleaned it out with the remaining MAF cleaner.

I'm uploading pictures because I'm not sure how to check IAC pins with multimeter as next step or even if I can with this particular attached model:

here's the intake manifold in there for reference. MAF is taken out at this point: http://i.imgur.com/zjsj2Pp.jpg
here is the intake manifold taken out and me holding it roughly where it connects: http://i.imgur.com/NF6mFD3.jpg
here is the motor side of the intake manifold before cleaning: http://i.imgur.com/RRrdg65.jpg
here is the air side before cleaning: http://i.imgur.com/DYGj3Wv.jpg
here is a view of what I take to be the IAC attached to the intake manifold: http://i.imgur.com/szQc1wx.jpg
here is the back view of the IAC: http://i.imgur.com/s0LecZT.jpg
here is a closeup of one side of the pins that attach it to the intake manifold: http://i.imgur.com/NqdHgli.jpg
here is a view of the other side of that pin: http://i.imgur.com/leHskjr.jpg
and that's all I've got

So...can I test this IAC with a multimeter? If not, what should I do next? try replacing MAF and the intake manifold piece? then if it still doesn't work check for vacuum leaks?
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Old 11-22-2015, 11:24 AM   #8
twitchyboy
 
Drives: 08 Yaris Sedan 5spd
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hey guys,

Looks like I celebrated too soon. The idle returned to fluctuating between 500-750 after I took it out on the interstate at 3500rpm for 15 minutes. So, I took out the throttle body and found out the IAC is an integrated part of it that can't be detached, disassembled, and cleaned.

Soo, I cleaned a tiny bit of gunk out of the butterfly valve and put the throttle body back in the engine. Now my idle ranges between 750 and 1000 rpm. Is there anything else I can check for or do before giving it up and taking it into the mechanic? Like I read something about trying to disconnect the battery and getting the throttle body to relearn? Would that even fix the variable idle issue?

Also: My car screeched this morning upon cold startup. Hadn't noticed this before.

Last edited by twitchyboy; 11-22-2015 at 11:40 AM. Reason: add pictures
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Old 11-22-2015, 11:34 AM   #9
twitchyboy
 
Drives: 08 Yaris Sedan 5spd
Join Date: Nov 2015
Location: Kansas City, Missouri
Posts: 6
pictures:

throttle body is located below the radiator fluid cap in this picture



TB Engine side



TB Air side



IAC looks integrated



IAC definitely integrated

http://i.imgur.com/s0LecZT.jpg

Riveted on :(

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Old 11-22-2015, 11:43 AM   #10
Rigaud
 
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Quote:
Originally Posted by twitchyboy View Post
hey guys,

Looks like I celebrated too soon. The idle returned to fluctuating between 500-750 after I took it out on the interstate at 3500rpm for 15 minutes. So, I took out the throttle body and found out the IAC is an integrated part of it that can't be detached, disassembled, and cleaned.

Soo, I cleaned a tiny bit of gunk out of the butterfly valve and put the throttle body back in the engine. Now my idle ranges between 750 and 1000 rpm. Is there anything else I can check for or do before giving it up and taking it into the mechanic? Like I read something about trying to disconnect the battery and getting the throttle body to relearn? Would that even fix the variable idle issue?

Also: My car screeched this morning upon cold startup. Hadn't noticed this before.
Did you check all vacuum lines like we strongly suggested?
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Old 11-22-2015, 12:00 PM   #11
twitchyboy
 
Drives: 08 Yaris Sedan 5spd
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Nossir - how do I do that?
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Old 11-22-2015, 12:14 PM   #12
tmontague
 
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Easiest way it to buy an ultragauge (or other scan tool) and set it on short and long term fuel trim while the car is idling. Then Rev the car to 2500rpm an see how the values change.

If the long term trim is showing a high positive # under idle but not at 2500rpm then it likely has a vacuum leak.

You should hear a his from the area that is leaking. I personally light a stick of incense and watch where the smoke is being sucked into on the engine to find the specific area of a leak.

Keep in mind after resetting the ECU your engine will idle a little erratically for a few hundred km's
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