Idle Air Control Valve

[prix]

Would a dirty or faulty idle air control valve have any effect the firmness of power steering? I am having a problem with really stiff steering and occasional low idle/engine dying at stops or slow downs. I do mostly "around town" driving, meaning 25-40 mph a lot of the time in stop and go traffic. I don't know why, but one thing I have noticed is that the power steering gets stiff for a time before I am going to have an 'engine dying' episode. Sometimes i will notice this stiffness for several days before I have an 'episode'. After the stall out, the car always starts right back up agaiin. I have had throttle cleaned, fuel filter replaced..and the problem continues. Once the car restarts, the steering is light and easy again (until the cycle starts again). What is going on? Should I clean and/or replace the idle air control valve? Why is the steering stiffening up at times, then being completely smooth and easy at other times (i.e., after the car is restarted)? Thank you to all.

[dfkd]

It could affect the steering because if the idle is too low then the pump wont be able to turn fast enough.

Put on the a/c at the same time and see what happens. If it stiffens up with the a/c on then it could well be the IAC because it is responsible for speeding up the idle to absorb the higher energy requirements of the a/c at idle.

[prix]

Thanks for the input. I will try this to see if I can find some correlation.

It could affect the steering because if the idle is too low then the pump wont be able to turn fast enough.

Put on the a/c at the same time and see what happens. If it stiffens up with the a/c on then it could well be the IAC because it is responsible for speeding up the idle to absorb the higher energy requirements of the a/c at idle.

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[wwest]

Most modern day idle air bypass systems use a PWM signal to "linearly" control a solenoid. The engine ECU my need to be reset so disconnect the battery for 10 or 15 minutes and then drive the car a few miles.

[SRK]

Engine RPM under most conditions is controlled by the ECM, so that when you increase electrical load (headlights) or AC load, or the engine is in warm up, the computer controls RPM against a pre-set value. Base idle is the same.

The only time it doesn't, is when the steering is at full lock and the power steering pump deadheads against the rack, and the spike in pressure opens the air valve which bypasses the throttle plate and increases RPM mechanically. Why Lexus does this when many other manufacturers don't is beyond me. That's my understanding of the idle air valve on the pump, and if you follow the air lines you will see that that is all they do.

[monarch]

I wonder if the shop that installed your power steering pump installed the air control valve correctly and routed the two attaching vacuum hoses correctly?

http://i5.photobucket.com/albums/y189/mastertech/psair.jpg

http://i5.photobucket.com/albums/y189/mastertech/psairb.jpg

[914lps]

I wonder if the shop that installed your power steering pump installed the air control valve correctly and routed the two attaching vacuum hoses correctly?

http://i5.photobucket.com/albums/y189/mastertech/psair.jpg

http://i5.photobucket.com/albums/y189/mastertech/psairb.jpg

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Monarch,

I was wondering this same thing about my car (vacum lines on right). In fact that is why I loged on today. As you know Pep Boys replaced my Power Steering pump after the almost new one failed when I was on a trip.

The old pump clearly shows the main bearing on the outside of the pump failed. The bearing self distructed.

The car did not leak fluid or smoke. When the old pump was removed it had fluid in it.

After Pep Boys put the new pump on, the car started smoking like crazy. But not till the new pump was on. Pep Boys then told me they fixed it and the air valve was OK. I did tell them to replace it if needed.

On getting home I found out they broke off the fitting from the Air intake, and pluged that vacume line. They left the line conected to the manifold by the Lexus logo.

I "fixed" the fitting and conected the vacume line to the air intake. Bag! Car smoked. And smoked bad. Lots of oil going though the line going into the Air intake conection piont. I have not detected any oil going into the manafold from the vacum line conetec to the manifold.

I tried to check to see if the vacum lines are conected corectly. I'm not able to get a look at them, but doing it by touch, the line closest to the front of the car is going to the manifold, and the one on the "back" is going to the air intake conection. Is this right?

Also could the valve get damadged in moving it from on pump to the other? If the vacum lines are crossed, what would that do?

I have for now pluged both lines. I have not noticed the difreance in the way the car drives.

More then likly I'm going to get some vacum line and use it to temporaly swith the vacum lines to each others conections, to see if that fixes it. If so, I'll know they crossed the lines.

I know I can get a new valve off Ebay for about $75.00 with shipping.

Thanks in advance for the help.

[prix]

I was having this same problem with stiff steering BEFORE I got this new power steering system put in, so I don't thnk it was anything the mechanic did. Same deal with intermittent stiff steering, then a stall. I'd had a leaking pump and rack for wa-a-a-y too long, so went whole hog and replaced everything (I was going to fix those leaks once and for all!). I thought the stiff steering issue was related to all those leaks...and I was looking foward to smooth power steering once again.

Disappointed to say the least that the steering was stiff when I drove it away from the shop after getting the new system. It was pretty bad that first day. Seemed to loosen up a little the second day. An alignment helped a little, but clearly that wasn't the entire problem because the stiffness came right back. But three or four days later, when the car stalled out, steering immediately became PERFECT. Light as a feather; I could have parked that car with one finger on the steering wheel. After a day passes? I'm right back to stiff steering.

I did turn on the AC at some point today (trying that test someone mentioned) and it did seem that the steering got worse when I did, which would point to the idle air control valve, as someone said. but I need to try that again to know for sure. I have to wait for it to stall out again (so the steering will once again be perfect), then immediately turn on the AC and see whether it immediately stiffens up.

If I wait too long after the stall to turn on the AC (which was the case today), I will have no way of knowing whether the stiffness was brought on by running the AC, or just because enough time has passed for it to start stiffening up again.

The mechanic thinks it's the computer chip. If it's a cheaper IAC part, I'd rather fix that first. The throttle was never removed and officially cleaned, btw, but was merely sprayed and 'cleaned up'. He did say he saw a lot of deposit. So I guess I could have him thoroughly clean the throttle and the IAC and see if that stops it.

Did anyone ever try that $99 dollar deal posted on that lengthy thread started by Bob (low idle/engine dying)? Where they rebuild the ECU? That might be the next step, if these others don't work.

[prix]

what does this mean..."when the steering is in full lock"? thanks.

Engine RPM under most conditions is controlled by the ECM, so that when you increase electrical load (headlights) or AC load, or the engine is in warm up, the computer controls RPM against a pre-set value.  Base idle is the same.

The only time it doesn't, is when the steering is at full lock and the power steering pump deadheads against the rack, and the spike in pressure opens the air valve which bypasses the throttle plate and increases RPM mechanically.  Why Lexus does this when many other manufacturers don't is beyond me.  That's my understanding of the idle air valve on the pump, and if you follow the air lines you will see that that is all they do.

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[prix]

Thanks Monarch. The photos are very helpful. I finally get to see what an air control valve looks like. Mechanic seems very knowledgeable (a former Lexus dealer mechanic), so I would imagine it's hooked up okay. I'll have a look see.

I wonder if the shop that installed your power steering pump installed the air control valve correctly and routed the two attaching vacuum hoses correctly?

http://i5.photobucket.com/albums/y189/mastertech/psair.jpg

http://i5.photobucket.com/albums/y189/mastertech/psairb.jpg

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[prix]

I must say, your experience sounds like a complete nightmare. You could always stop around to your dealer or friendly neighborhood mechanic and have them tell you whether the lines are hooked up in the right place...from monarch's photo, looks to me like that IAC just screws in, but I really don't know.

I wonder if the shop that installed your power steering pump installed the air control valve correctly and routed the two attaching vacuum hoses correctly?

http://i5.photobucket.com/albums/y189/mastertech/psair.jpg

http://i5.photobucket.com/albums/y189/mastertech/psairb.jpg

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Monarch,

I was wondering this same thing about my car (vacum lines on right). In fact that is why I loged on today. As you know Pep Boys replaced my Power Steering pump after the almost new one failed when I was on a trip.

The old pump clearly shows the main bearing on the outside of the pump failed. The bearing self distructed.

The car did not leak fluid or smoke. When the old pump was removed it had fluid in it.

After Pep Boys put the new pump on, the car started smoking like crazy. But not till the new pump was on. Pep Boys then told me they fixed it and the air valve was OK. I did tell them to replace it if needed.

On getting home I found out they broke off the fitting from the Air intake, and pluged that vacume line. They left the line conected to the manifold by the Lexus logo.

I "fixed" the fitting and conected the vacume line to the air intake. Bag! Car smoked. And smoked bad. Lots of oil going though the line going into the Air intake conection piont. I have not detected any oil going into the manafold from the vacum line conetec to the manifold.

I tried to check to see if the vacum lines are conected corectly. I'm not able to get a look at them, but doing it by touch, the line closest to the front of the car is going to the manifold, and the one on the "back" is going to the air intake conection. Is this right?

Also could the valve get damadged in moving it from on pump to the other? If the vacum lines are crossed, what would that do?

I have for now pluged both lines. I have not noticed the difreance in the way the car drives.

More then likly I'm going to get some vacum line and use it to temporaly swith the vacum lines to each others conections, to see if that fixes it. If so, I'll know they crossed the lines.

I know I can get a new valve off Ebay for about $75.00 with shipping.

Thanks in advance for the help.

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[prix]

Is the battery disconnected during an alignment? I ask, because the power steering was perfect after the alignment was done (for about five minutes of driving, then it stiffened right up again). Thanks.

Most modern day idle air bypass systems use a PWM signal to "linearly" control a solenoid. The engine ECU my need to be reset so disconnect the battery for 10 or 15 minutes and then drive the car a few miles.

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[SRK]

what does this mean..."when the steering is in full lock"? thanks.

[

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That means you have the steering wheel hard over to the left or right.

[914lps]

Is the battery disconnected during an alignment?  I ask, because the power steering was perfect after the alignment was done (for about five minutes of driving, then it stiffened right up again).  Thanks.

Most modern day idle air bypass systems use a PWM signal to "linearly" control a solenoid. The engine ECU my need to be reset so disconnect the battery for 10 or 15 minutes and then drive the car a few miles.

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No reason to touch the battery on doing an alignment that I know or can think of.

[prix]

thanks srk and 914. i'm going to try disconnecting the battery tomorrow to reset the computer (as a previous poster suggested). i'll also test out that A/C theory (turn the A/C on to see if it makes steering stiffer, or if it makes it worse). then maybe throttle cleaning and cleaning and/or checking the IAC valve. If it looks faulty, replace that. The last option will be the computer chip. I'll post back here to let you know how I get this resolved. thanks again...

Is the battery disconnected during an alignment?  I ask, because the power steering was perfect after the alignment was done (for about five minutes of driving, then it stiffened right up again).  Thanks.

Most modern day idle air bypass systems use a PWM signal to "linearly" control a solenoid. The engine ECU my need to be reset so disconnect the battery for 10 or 15 minutes and then drive the car a few miles.

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No reason to touch the battery on doing an alignment that I know or can think of.

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[prix]

SRK -- Need clarification. Sounds like you are saying that if the IAC valve closes off and the car dies, that this is controlled by the computer (and not caused by a faulty IAC valve?). The other day, I put the car in park and kept turning the AC on and off trying to get the engine to konk out. I almost succeeded a few times, when the idle dipped down to 100=200 after I turned on the AC. But each time it caught it and the RPMs went back up. I'm sure if I'd tried that long enough I could have made it die. IN another thread (that long thread about low idle/engine dying), Bob is saying he's convinced it's the IAC closing off that is causing the engine to konk. Once it does konk, and once you restart the engine, then that IAC valve is open again which is why the steering returns to normal after a stall out. As I said, for hte most part the RPMs behave normally. It's when I turn on the AC or come to a slow down or up to a stop sign after driving around town for a time that it drops very low and stalls out. Steering is always stiff prior to a stall out. Thanks.

Engine RPM under most conditions is controlled by the ECM, so that when you increase electrical load (headlights) or AC load, or the engine is in warm up, the computer controls RPM against a pre-set value.  Base idle is the same.

The only time it doesn't, is when the steering is at full lock and the power steering pump deadheads against the rack, and the spike in pressure opens the air valve which bypasses the throttle plate and increases RPM mechanically.  Why Lexus does this when many other manufacturers don't is beyond me.  That's my understanding of the idle air valve on the pump, and if you follow the air lines you will see that that is all they do.

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[dfkd]

SRK -- Need clarification.  Sounds like you are saying that if the IAC valve closes off and the car dies, that this is controlled by the computer (and not caused by a faulty IAC valve?).  The other day, I put the car in park and kept turning the AC on and off trying to get the engine to konk out.  I almost succeeded a few times, when the idle dipped down to 100=200 after I turned on the AC.  But each time it caught it and the RPMs went back up.  I'm sure if I'd tried that long enough I could have made it die.  IN another thread (that long thread about low idle/engine dying), Bob is saying he's convinced it's the IAC closing off that is causing the engine to konk.  Once it does konk, and once you restart the engine, then that IAC valve is open again which is why the steering returns to normal after a stall out. As I said, for hte most part the RPMs behave normally.  It's when I turn on the AC or come to a slow down or up to a stop sign after driving around town for a time that it drops very low and stalls out.  Steering is always stiff prior to a stall out.  Thanks.

Engine RPM under most conditions is controlled by the ECM, so that when you increase electrical load (headlights) or AC load, or the engine is in warm up, the computer controls RPM against a pre-set value.  Base idle is the same.

The only time it doesn't, is when the steering is at full lock and the power steering pump deadheads against the rack, and the spike in pressure opens the air valve which bypasses the throttle plate and increases RPM mechanically.  Why Lexus does this when many other manufacturers don't is beyond me.  That's my understanding of the idle air valve on the pump, and if you follow the air lines you will see that that is all they do.

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Steering will always get stiff if the engine speed is too low so that is just a resulting symptom and not the actual problem.

I had the same issue on an old taurus i had (thus the a/c suggestion). Steering would be stiff at idle esp with a/c on. I ended up changing the iac on that car and it fixed the problem.

I figured out it was the iac by unplugging it and noting that the idle though slower but more stable with it unplugged.

I dont know how different, if at all, it is with the lex tho.

The IAC should never really "close off" but just regulate the air supply. It is controlled by the ecu though, however, the fact that it does respond to the a/c being turned on means that it is working but maybe not as well as it should.

Cleaning the inside mechanics of the IAC on the taurus helped a lot when i did it. Seems that it may have just been dirty and that was restricting its movement. I used electrical contact cleaner to do mine (works and leaves no residue).

What's for sure though is that it isnt your steering that has a problem.

[prix]

UPDATE: disconnected battery this AM to reset the computer. fun trying to remember my security code to disarm the antitheft device on the radio though...so fifteen minutes later, i'm driving along and suddenly i 'knew' what the three number code. info was apparently buried deep within the brain.

after disconnect, for three seconds or so, the steering was light as a feather, then reverted to firmer feel (sort of feels like it has a drag on it when turning the wheel). hmm..

but the disconnect did fix one problem! incredibly, the jet engine sound that started four days ago around the PS pump area WENT AWAY! i could not believe my ears. no more high pitched whine! i now think that SK (SRK?)'s suggestion that when the mechanic degreased the pump (sprayed heavily with degreaser followed by water), that a wire got wet? why else would this whine completely disappear??? not complaining of course.

anyhow, steering 'problem' remains; it's improved since the disconnect, but still not the way i'd like. will investigate throttle and idle control valve and report back. onwards and sideways...

thanks srk and 914.  i'm going to try disconnecting the battery tomorrow to reset the computer (as a previous poster suggested).  i'll also test out that A/C theory (turn the A/C on to see if it makes steering stiffer, or if it makes it worse).  then maybe throttle cleaning and cleaning and/or checking the IAC valve.  If it looks faulty, replace that.  The last option will be the computer chip.  I'll post back here to let you know how I get this resolved.  thanks again...

Is the battery disconnected during an alignment?  I ask, because the power steering was perfect after the alignment was done (for about five minutes of driving, then it stiffened right up again).  Thanks.

Most modern day idle air bypass systems use a PWM signal to "linearly" control a solenoid. The engine ECU my need to be reset so disconnect the battery for 10 or 15 minutes and then drive the car a few miles.

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No reason to touch the battery on doing an alignment that I know or can think of.

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[prix]

when you say iac, do you mean the 620 part that is part of the throttle (or connected to it, i am not quite sure), or do you mean the idle air control valve assembly which costs around 100 and is on the power steering line? i was told by a parts guy that they sell a lot of that cheaper part, but have never sold even one of the 620 part. i pray you are referring to the idle air control valve assembly (on the power steering line). learned too that if it were a mass sensor, that i would have seen a huge plume of white smoke caused by oil backing up into the manifold. well, i do not have that problem, so i don't think that's it. mechanic said mass sensors rarely go out anyway. my symptoms sound an awful lot like what you experienced with the taurus. stiff steering with the a/c on, stiff at low idle, etc. i've noticed that car is idling lower than it should by anywhere from 200-300 rpms. will have it looked at next week and hopefully get this resolved. would like to know which of these two parts you are talking about before i take the car in though. please feel free to PM me or send email? thanks.

SRK -- Need clarification.  Sounds like you are saying that if the IAC valve closes off and the car dies, that this is controlled by the computer (and not caused by a faulty IAC valve?).  The other day, I put the car in park and kept turning the AC on and off trying to get the engine to konk out.  I almost succeeded a few times, when the idle dipped down to 100=200 after I turned on the AC.  But each time it caught it and the RPMs went back up.  I'm sure if I'd tried that long enough I could have made it die.  IN another thread (that long thread about low idle/engine dying), Bob is saying he's convinced it's the IAC closing off that is causing the engine to konk.  Once it does konk, and once you restart the engine, then that IAC valve is open again which is why the steering returns to normal after a stall out. As I said, for hte most part the RPMs behave normally.  It's when I turn on the AC or come to a slow down or up to a stop sign after driving around town for a time that it drops very low and stalls out.  Steering is always stiff prior to a stall out.  Thanks.

Engine RPM under most conditions is controlled by the ECM, so that when you increase electrical load (headlights) or AC load, or the engine is in warm up, the computer controls RPM against a pre-set value.  Base idle is the same.

The only time it doesn't, is when the steering is at full lock and the power steering pump deadheads against the rack, and the spike in pressure opens the air valve which bypasses the throttle plate and increases RPM mechanically.  Why Lexus does this when many other manufacturers don't is beyond me.  That's my understanding of the idle air valve on the pump, and if you follow the air lines you will see that that is all they do.

←

←

Steering will always get stiff if the engine speed is too low so that is just a resulting symptom and not the actual problem.

I had the same issue on an old taurus i had (thus the a/c suggestion). Steering would be stiff at idle esp with a/c on. I ended up changing the iac on that car and it fixed the problem.

I figured out it was the iac by unplugging it and noting that the idle though slower but more stable with it unplugged.

I dont know how different, if at all, it is with the lex tho.

The IAC should never really "close off" but just regulate the air supply. It is controlled by the ecu though, however, the fact that it does respond to the a/c being turned on means that it is working but maybe not as well as it should.

Cleaning the inside mechanics of the IAC on the taurus helped a lot when i did it. Seems that it may have just been dirty and that was restricting its movement. I used electrical contact cleaner to do mine (works and leaves no residue).

What's for sure though is that it isnt your steering that has a problem.

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