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High idle (hot or cold)

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cold high hot idle
35K views 5 replies 5 participants last post by  pcflctnh 
#1 ·
2005 CE with 108k miles. Just changed the timing belt, water pump, spark plugs, and air filter. After initial startup, I noticed the engine was staying at a high idle...1200 rpm. My wife drives the van usually so I don't know if this had been going on before. I drove the van and noticed that it seemed to surge when downshifting...like the rpm's would jump between gears. I checked all vaccuum hoses and wiring. Everything seems to be ok. Same rpm when hot. I'm very tired of working on it so I'm nearly ready to take it to the stealership to diagnose. I would prefer to find the problem myself, fix it, and finally stand back and say "job well done". Any thoughts on what the problem might be?
 
#2 ·
Sounds suspiciously like a vacuum leak. i would go through the throttle body area again.


HunterTom said:
2005 CE with 108k miles. Just changed the timing belt, water pump, spark plugs, and air filter. After initial startup, I noticed the engine was staying at a high idle...1200 rpm. My wife drives the van usually so I don't know if this had been going on before. I drove the van and noticed that it seemed to surge when downshifting...like the rpm's would jump between gears. I checked all vaccuum hoses and wiring. Everything seems to be ok. Same rpm when hot. I'm very tired of working on it so I'm nearly ready to take it to the stealership to diagnose. I would prefer to find the problem myself, fix it, and finally stand back and say "job well done". Any thoughts on what the problem might be?
 
#3 ·
I second the vaccum leak check.... check for disconnected hoses or cracked ends on the hoses.
 
#4 ·
Did you clean the throttle body by any chance? This will cause a higher than normal idle. It will take some time for the computer to relearn the target RPM. There is no IAC motor to control idle on the second gen siennas. The computer controls the throttle plate at an angle to control idle RPM. Now if you clean the throttle body bore you have more air going around the plate causing a higher idle. In this case disconnect the battery and it should reset the throttle plate.

Side note: If you disconnect the battery and don't clean the throttle body you will have a lower RPM at idle due to the build up of residue(if you will) and less air can by-pass the throttle plate.


I would be interesting in knowing how you did the plugs? Remove the plentum? A bunch of us are looking to tackle this job. Please any details would be great. ;)
 
#5 ·
Ahhhh...job well done! Thanks for the tip robo5. I had actually just (skeptically) pulled the neg battery cable and came back in to find your post. Good timing. Plugged it back in and took the van for a short drive. Put it in park in the garage, and she dropped right down to maybe 650 rpm. I did clean the TB by the way, but I think maybe more importantly, I replaced a terribly dirty air filter...thought my wife's oil change place had been checking it. I know, I know...bad DIYer

Changing spark plugs is quite a job in itself, but I am more than happy to share my experience. Actually, I intend to conjure up a little piece on my lessons learned over the whole project. I'll drop that in a different thread, but I can share some of the spark plug experience here.

Of course the 1st step is to remove the engine cover and then the wipers, wiper motor, and cowling...annoying but necessary. Then I removed the air cleaner cap and disconnected that subassembly from the throttle body. Then I removed the throttle body itself. That comes off in two sections and exposes two rubber gaskets. I had ordered the gaskets through Autozone the previous day just in case, but I thought they were still in pretty good shape so I reused them. Now I had intentionally delayed reinstalling a couple components from the timing belt job in hopes of making my spark plug job easier...specifically the "engine moving control rod" and the "engine mounting stay No.2"...both on the passenger side of the engine. With all that stuff removed, I now had access (albeit very limited access) to all 6 spark plugs.

The front three should be no problem of course. You just pull out the 10mm hex head bolt, unplug the wire, pull out the coil, and then use a deep well socket with an extension to get to the spark plug. Sounds easy. Use a very thin flat head screwdriver to pull up the little clip that holds the wire on. I broke one, but it still clips on ok. One of the bolts holding one of the coils on was kinda hard to get out. It turned a while and then stopped. I panicked and decided to skip that plug. As I screwed that bolt back in it snapped. It must have been bent or cross threaded at the factory. Enough was still sticking out to grab with a set of vice grips. Got it out, retapped the hole, and filled with a zinc plated bolt from Home Depot. Worked fine. I also used a flat head screwdriver to help pop out the coils. Just be careful with those as they will break.

The back three are the troublesome ones. You'll want to experiment with the front three a little. You're going to want a socket/extension combination that is long enough to reach the plug but small enough to maneuver in extremely tight spaces. I ended up with a 7cm (2.75in) extension, a swivel attachment that extended another 4cm (1.5in), and then a 16mm deep well socket that extended it another 6.5cm (2.5in). So basically, from the edge of the ratchet to the tip of the socket, I had about 16cm or 6.25inches. See pic... Working from the throttle body side, I was able to get the two plugs on that side. Luckily, I think I'm the perfect build for such a job. I'm tall, skinny, and have small hands. That's what it takes. After you unclip the wire and remove the bolt, there is enough clearance to remove the coil and get at the plug. Clearance is very tight on the passenger side plug, but it can be done. The coil is rubber at the bottom which is necessary to bend over a bit. Take a big shot of patience before tackling this job. It takes careful steady and patient hands to get it done. At times I had my left arm around the left side of the intake and my right arm around the right side. From there I just worked by feel. You will lose some skin off of your forearms in the process. Don't forget to dab a little anti-seize on the threads before putting in the new plugs. I used the manufacturer suggested iridium plugs. They sure are expensive, but I don't want to do this job again for a long time. Feel free to ask for any suggestions or pictures or whatever. I would be more than happy to help. Have fun and thanks again for the reply.
 

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#6 ·
I had the timing belt replace at a reputable repair garage about four months ago and at that time the technicians cleaned the injectors and the throttle body and when I picked up the 2005 van it wouldn't come down off the high idle so I returned and the manager told me that the technician didn't disconnect the battery to reset the idle so they did that and the idle seemed to be ok for awhile then the problem reoccurred so I decided to take the van back to the dealer where I purchased it in 2005 which is about 35 miles away, when I arrived the idle was normal and the service writer told me what is written here about computer having to learn the idle speed. Now the idle speed problem comes and goes intermittingly so I am trying to be patient and hopefully the problem will someday not be there at all.
 
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