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Discussion Starter #1
Hey guys- I have a 97 T100 SR5, MT. I rebuilt the engine with new heads and timing components after a HG failure about 2 months ago.

Since the rebuild, I have only driven around town back and forth to work, about 10 miles each way. No problems, no codes.

I took the T on a road trip about 4 hours, and It started doing an intermittent high idle when engine was warm, around 1500. I'd hit the gas and it would slowly fall back down to 700.

I took the throttle body off, cleaned it up, took the IAC off and cleaned that too and blew it all out with air. I cleaned the MAF too with the safe cleaner.

It didn't make much of a difference.

No codes, and still idles at 1500 ish, most of the time now.

I need to get a multi-meter from work and check the resistance on the IAC.

Linkage all looks good, nothing binding there, but I sprayed it all down with white lithium grease

Can't find any vacuum leaks, and because it doesn't do it all the time I don't suspect a vacuum leak.

Dashpot looks good, I can press down on the throttle all the way while running and it will get back down to 600-700.

I can get some play out of the shaft axially, and from other research I think that may be my problem. I have ready that others with a similar problem have put in o-ring in there between the TB and springs/on the shaft with good results.

I guess maybe a bushing is supposed to sit there and wears out?

So anyone have any suggestions or experienced this? I'll check the IAC with a meter, but it looked pretty clean in there, so I'm leaning towards the O-ring thing.
From my understanding there is no "rebuild" kit for a throttle body. Toyota sells it complete, and my local wrecking yards are at least 100 bucks, condition unknown.

Thanks in advance for the help- Brian
 

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Reading your post title I was ready to say IAC. You said you cleaned it though.

I had the same high idle. I cleaned the IAC and it fixed it for about a month.

Maybe it is going bad? Dunno.

With a dirty IAC I would stay on high idle at my initial morning start up. The RPMs would not drop like they're supposed to after warm up.

Is the throttle cable rusty or getting stuck? How is the return spring on the TB( never saw one fail actually)...

I would guess w/o a code, it might be something mechanical as opposed to a senosor. A sensor would set a code in the ECU. Mechanical, like a sticky spring on the TB for example, could cause issues and set no code.
 

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Sounds like it could be the throttle body throttle plate shaft. It's been know to wear and cause an intermittent vacuum leak like yer situation. You could try the starter spray around the throttle body when it happens and see if the RPMs go up or not. I think someone said the fix was pretty simple by adding an extra spring wave washer to shim up the looseness. ;)

Good luck! :D
 

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NorCal Chapter Pres
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My rig has 150k miles and is starting to idle high sometimes. 1100k rpm. Scangauge shows 28* for the timing, and when the idle is normal that number is in the 8* range...
 

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Discussion Starter #5
update- I loosened the dashpot screw all the way off and it seemed to have taken care of my high idle issue, and I tightened the 12MM nut on the end of the shaft too. I will probably take off the dashpot and clean it up, and maybe find a new one.
 

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NorCal Chapter Pres
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high idle is back, I'm gonna tear into this TB again this weekend. I suspect the side to side play inside is causing this to happen.

I will try something like this;

http://www.toyota-4runner.org/3rd-gen-t4rs/123396-my-high-idle-cured.html

I'll keep you guys posted on the outcome
I did the same fix, I did it on the side of the road. It worked for a day too and came back...

I sprayed carb cleaner around the tb when it was high idling the other day, no change in RPM. I unplugged the TPS, no change. Unplugged the IAC, the RPM's rose.

I put a Vac gauge on the line that feeds the actuator next to the TPS. 22mmhg at idle. I put the mityvac on the actuator, and plugged the vac line on the motor side. I applied a vaccum to bring the idle down, and it was still high, about 900 rpm. This ruled out that actuator.

I'm going bezerk. I did read that when a crankshaft position sensor is on its way out, ti can lead to a high idle. Which would make sense as to why my ignition timing is at 20+ degrees at idle. I also have 150k miles and the a/f sensor in front of the cats is stock, so I may change that first...
 

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Discussion Starter #8
Norcal- the fix you did, was it the shim like in the write-up or the dashpot set screw? I def have side to side play in the valve. When I'm running out at faster than 50 mph and slow down it's fine, below 1000, and eventually creeps down to 700. When I'm going slow, and then brake or put it in neutral it still stays kinda high like 1500.

I don't have a scan gauge, otherwise I'd compare my timing to yours. When I cleaned the TB the first time I took off the TPS and it looked pretty good in there. I think for me leaning towards the TB just being worn on the shaft. I'll let you know after this weekend what I find. If that doesn't work I might just find a used TB and throw that on there.

but I still need to put a meter on the IAC and test that.
 

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NorCal Chapter Pres
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I think I fixed mine. Hard to tell since it's an intermittent issue, but it hasn't come back in the last 300 miles I put on my truck...

I checked the TB shaft screw. Was tight and had no play. When running, and under high idle, I sprayed carb cleaner and held an unlit propane torch around the TB. No changes...

I ended up cleaning the Air filter since it was dirty. I also had a feeling the IAC was acting up, so I completely dissembled it. I removed the motor magnet assembly, and the other side where the coiled spring was. I marked the plate before removing it so I made sure I could put it back in one spot.

One thing I did notice is that the plastic bushing that rides against the IAC shaft, and the coiled spring, was black around the whole edge, almost gummed up. My theory was that it was causing the IAC to stick.

I cleaned the plastic bushing, and the bearing. With everything apart, I could also spin the IAC shaft almost 360 degrees, and clean every bit of it. A couple spots had some mild buildup, that could have led to the IAC sticking.

I also applied a couple drops of thin oil to the IAC bearing, on both the coil spring side and magnetic rotor aside. I made sure no excess was in the IAC or on the rotor assembly.

Sealed back up and reassembled the truck. Once the truck warmed up, the idle stayed at 700 RPM +/- 10 rpm according to scangauge.
 

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Discussion Starter #10
Bumping this up.

I fixed it, loosened the 12 mm nut on the tb shaft, carefully pulled off the spring assembly, put an o-ring then washer, re-installed the assembly. I also pulled alittle more spring through the stop to tighten it up alittle. Works beautifully now.
 
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