Engine Idle Too High

[lexus082]

I just recently had the starter replaced and both TPS sensors replaced. The idle is too high. Toyota hooked the car up to a tachometer and it idled at 715 rpms. But, the engine is actually running at a higher rpm than what the tach. is stating. Then when you turn on the AC the rpms drop to about 580-600 rpms. Toyota mechanic said the engine isn't getting the proper tach signal. If I'm driving on a flat road going 40mph and I take my foot of the accelerator the car will continue to do 40mph by itself. Also when the car is first started, instead of it warming up and the idle starts to drop lower, as the engine warms up the rpm's also increase and then it looks like its idling at 900 rpms. There's no check engine light on at all, only a TRAC light comes on and not all the time. That maybe related to something else. The check engine light was on but went off after installed the TPS sensors. Would greatly appreciate the help. I just spent alot on the starter and the tps being installed. I have a feeling the Lexus bill could be quite high also if I can't troubleshoot this either.

[qha_vn]

why did you replace the TPS sensor? dd you have any issue with idle speed before TPS sensor replaced?

in my best guess, when replacing the TPS, the throttle valve can not fully close when your foot off acceleration pedal. this may cause by stuck valve or the acceleration wire has not enough "free-play"

another area to check is the idle valve

[lexus082]

The check engine light came on and I took it to the dealer and they said the TPS sensor was bad. The mechanic and I checked the cables annd they aren't to tight. The check engine light went off, but I still have a TRAC light on which may be related to something else...

[fencera]

You mentioned that your TRAC light sometimes comes on but not all the time. I have a similar issue and it is related to my idle speed. I recently cleaned the throttle body and stupidly took off both the TPS and trac sensor. When it came time to put them back on, I did not do so correctly. I found the idle speed can be adjusted by rotating the TPS sensor. The plastic body holding it allows for rotation and adjustment of the idle speed when the screws retaining it are loosened some. With some time and patience, I was able to get my idle speed back to where it should be.

However, my TRAC light still comes on sometimes. Oddly enough, it is directly related to how long I have the key in the ACC position before starting the car. If I immediately start the car, it normally won't come on. If the key sits in the ACC position too long, there are a series of clicks under the hood and the TRAC light will then come on and stay on. Given the only thing I did was remove the sensor from the throttle body, there must be some trick to getting it put back on correctly. Unfortunately, I have not been able to figure out what it is.

Good luck.

[qha_vn]

your right, i dont think the TRAC light on would cause idle issue because the the TRAC throttle valve becomes useless when the main throttle fully closes

fenceca gave a possibility of incorrectly installed TPS

[lexus082]

Well I took the car the Lexus and they said I need a new throttle body and a new traction control motor. I'm going to find out what exactly is wrong with the throttle body. Good news is they only are going to charge $105 for finding out those two things for me.

[lexus082]

Took off the throttle body and cleaned the entire thing. There was a lot of build up on the back of the butterfly valve. Also, Toyota didn't put back the throttle body with a gasket, they used some sort of sealant and it almost looked like it was sprayed and it also got all over the back of the butterfly valve and the throttle body. It is also very tacky and it might be my problem with the throttle sticking and idle problem. That throttle body cleaner is powerful stuff. I let the 2mm of build up soak in that stuff and it did a great job. Still have to go for a test drive.

[UCF3]

Where in MD are you? I might be able to troubleshoot the problem or go to my mechanic.

I thought it was the TPS as well, but you may have to replace a couple of 02 sensors as well

Email me at UCF3LOC@netscape.net if you're in the DC Area and you haven't solved the problem.

Took off the throttle body and cleaned the entire thing. There was a lot of build up on the back of the butterfly valve. Also, Toyota didn't put back the throttle body with a gasket, they used some sort of sealant and it almost looked like it was sprayed and it also got all over the back of the butterfly valve and the throttle body. It is also very tacky and it might be my problem with the throttle sticking and idle problem. That throttle body cleaner is powerful stuff. I let the 2mm of build up soak in that stuff and it did a great job. Still have to go for a test drive.

[lexus082]

Where in MD are you? I might be able to troubleshoot the problem or go to my mechanic.

I thought it was the TPS as well, but you may have to replace a couple of 02 sensors as well

Email me at UCF3LOC@netscape.net if you're in the DC Area and you haven't solved the problem.

The check engine light isn't on. Wouldn't it come on if the 02 sensors went bad. I went for a test drive and but it in park and the idle is still high. When you put the car in gear the rpms are normal. Its only in park/neutral when the rpms are at 900-1000. Both TPS sensors have been replaced main and sub-main. I didn't notice anything damaged on the throttle body? Its completely clean now. Its idles like the engine is cold but its not its completely warmed up and the rpms dont go back down. I just see the connection with the problem being the throttle body.

[qha_vn]

have you clean your idle speed valve?

[lexus082]

No I haven't cleaned it yet, thats the IACV correct? Is it difficult to clean it?

[qha_vn]

try cleaning and checking dash pot first (manual attached)

next should be IACV. you can find here the howto http://planetsoarer.com/

Note: soarer uses 1UZ-FE so engine is exactly the same as lexus ls400

dashpotd.pdf

[lexus082]

Thank you very much for sending me that file. I noticed this before hand, but I'm missing the cover that goes over top the filter and the other part called the seperater. I guess they fell off during removal when Toyota changed the starter. How they missed it I'm not sure. Do you think not having the filter, seperator and cap with throw off the idle speed and cause other problems?

[qha_vn]

if you are sure the cap and filter of the dash pot was missing after Toyota guys touched their hands on it. i guess you may want to go back on them and get them fix/replace the missing. it is there responsibility

regarding if the DP goes well without filter and cap or not, sorry i dont know, but you can follow the manual to check to make sure the DP operation is as expected.

glad to be helpful to somebody

[lexus082]

Well, I went to the Toyota dealer and they didn't think that the filter and the cap not being on there would cause the high idle. So I ordered a used throttle body w/ traction control. Thats what Lexus said was causing the high idle. I'm still not sure exactly what about the throttle body is causing it to idle high but I guess I'll find out when I swap them out. I still have a feeling its not the throttle body. Only one way to find out though. Lexus wanted $2300 to replace the throttle body and the traction control motor. So I will post the result of swapping out the throttle body. I hope Lexus is right.

[lexus082]

I adjusted the tps sensor by hand and was able to bring down the idle speed. I still believe there's still an issue with either the throttle body and or TPS sensor. I'm not sure if Toyota properly adjusted the tps using a multimeter or not. He said when he was turning it back and forth the idle didn't change?? Then he said it didn't really matter too much b/c the computer would overide it and correct it. Wasn't too sure about his method or thinking. By the way it was the same mechanic that told me he didn't know where to start and to take it to Lexus. It should be interesting to see what happens when I swap throttle bodies. Hopefully, the tps is correctly adjusted on the used throttle body I just bought but still waiting on to be delivered. Idle speed is no longer at 900-1000 rpms. Its now around 600 I think.

I am going to see what happens when I start the engine cold and see if it throttles down as the engine warms up. The rpms would go up as the engine got warmer before. It may just be that the tps sensor is out of adjustment, or like it was stated that the throttle body wasn't closing all the way which would eliminate the possibility of installing the tps properly. The car seems to drive better since idle speed has been lowered. The car actually revs higher than 1500 in some gears before it shifts.

[Robert Young]

If replacing the Lexus parts doesn't fix the problem, take a serious look at anything from the throttle body to the heads that might be leaking air (gasket failure, etc.). The emissions system will add fuel to ANY air leak in an attempt to keep the Ox sensor readings in balance and give you a high idle speed. Ford is notorious for this type of problem, normally created by a failed Nippon Denso valve that is used by their computer to adjust idle speed.

[lexus082]

One thing I was concerned about is that Toyota didn't replace any of the gaskets. On the throttle body for instance they just used this sticky, gold colored sealant. Now I am starting to think it may have something to do with that, like the intake manifold gaskets. Is there anyway one can check the vacuum pressure to see if there's any leaks within any of those gaskets?

[lexus082]

Well, today I swapped throttle bodies. Originally when I first got my car back from the Toyota dealer after replacing my starter the idle speed was too low and the car was shaking. They said the TPS sensor that was bad was probably causing the low idle. So I replaced the tps sensor and the idle speed was at 1000 rpms. I took the car back to the toyota dealer and they didn't know why the engine was idling so high. They told me to take it to Lexus. So I took it to Lexus and they said I needed a new throttle body. I bought one used off of ebay with 77,000 miles on it and swapped out throttle bodies today. Now... the engine idle is not at 1000 rpms and the engine does seem to idle down as it warms up from being cold. The only problem now is that the idle speed is too low and the car shakes. It now idles around 400-500 rpms which I believe is causing it to shake. It doesn't stall out, but the idle is very low. Any thoughts on this?

[LScott400]

This is for an LS, but it may help.......

EG351mfithrottlebody.pdf

[Threadcutter]

Well, I went to the Toyota dealer and they didn't think that the filter and the cap not being on there would cause the high idle. So I ordered a used throttle body w/ traction control. Thats what Lexus said was causing the high idle. I'm still not sure exactly what about the throttle body is causing it to idle high but I guess I'll find out when I swap them out. I still have a feeling its not the throttle body. Only one way to find out though. Lexus wanted $2300 to replace the throttle body and the traction control motor. So I will post the result of swapping out the throttle body. I hope Lexus is right.

082:

Gawd!, not the old "must be the throttle body" scam again.................

Replacing your throttle body is like ripping up and replacing the concrete on your driveway because it has oil stains on it.

I swear, I'm going to go into the throttle body exchange business....................It'll cost me $7 or $8 bucks worth of SeaFoam and about 15 minutes worth of elbow grease..........Sell an exchange for $1500 & I'll be "f*rting through silk"............

Nah, on second thought, I have more integrity than that............

[lexus082]

I totally agree with you. It didn't make any sense to me to replace the throttle body, but then again I'm not a Lexus tech. Or a Lexus dealer trying to make as much money as possible, even if it means replacing good working parts with new ones for $800 or so.

I talked to the ups mechanic at work and he said to check/clean the IACV. He explained to me that if it was gunked up it wouldn't allow as much air to pass through it, therefore causing the low idle speed. And then if the valve was working as it should it may not thow a CEL. So its believed that if I clean the valve it may open up the air passage way a little more which would allow more air in and then the computer would increase fuel, which in turn would increase the idle speed. Hopefully up to the normal idle speed

[lexus082]

I wasn't too surprised that my trac light hasn't been on since I have swapped throttle bodies. So the high idle is gone and the trac light went off. And just last night it seems that the traction control system is working just fine. And Lexus said it would be $2300 to fix this. Still not sure what traction control motor they were talking about. So other than the low idle speed everything is working and driving like its supposed to and I saved $2300.

[lexus082]

Well I cleaned out the IAC valve and it didn't help solve the low idle issue. It looks like its idling around 200 rpms or so. once it warms up to the normal operating temp. I didn't have a low idle before Toyota changed out the starter. So it's hard to tell if something went wrong with the car on its own for the two days it was at Toyota or if the Toyota mechanic messup something while changing the starter. I guess I could adjust that screw on the throttle body to let that throttle plate stay open a little more. Thats probably not the correct way to fix this, but not sure what to do now. The throttle body I picked up was from an sc with 70,000 miles so the tps sensor most likely hasn't needed to be adjusted and would leave me to believe its still calibrated from the factory.