I have an appointment booked for a shop because of an idle issue. I have been told it may be the IAC valve.

I have read about cleaning the valve with throttle body cleaner and a tooth brush.

Has anyone does this with good results?

I have been told the first step is to check the wiring as well as the valve with a multimeter.

The shop can't see me for another 8 days.


Thanks

 

Its fairly easy to clean. Unplug it and its held on by 3 12mm bolts, of course you can pay a shop $50 to do this if you want

 

The idle air control valves rarely ever fail on 4th gen Maxima's. Dont waste your money on replacing the idle air control valve without knowing its bad. Clean your throttle body as posted above.

 

I've cleaned mine with carb cleaner and toothbrush I probably wrote that post.

You will find some bolts and screws inside valve.
Some have springs and check valves behind them.
those passages should be cleaned as well.

The gasket can be reused, as I recall.
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Thanks. I have owned this car since day 1 and it has less than 112,000 miles on it. One day it is running fine, next day rough idle.

 

 

Rough idle? Could be a misfire. If someone was working on it they could of left a vaccuum hose unplugged

 

No one was working on it.

 

Sorry I thought I remembered reading it had just gotten out of the shop.
If cleaning the IACV makes no difference

You can start the car and remove 1 ignition coil at a time, if removing one of them makes no difference in your idle it means that cylinder is misfiring and causing your idle

 

Thanks. The car was in the shop for a CEL. All they got was a code for a knock sensor which they cleared. They detected the rough idle on a Friday afternoon heading into a long weekend here in British Columbia. I can't get the car back into the shop until the 14th.

 

They detected the rough idle? How about yourself? Your knock sensor code was probably on bc it's bad, but this will just cause your car to run sluggish and maybe a little gas mileage. What RPM does your car idle at when it's fully warmed up? Is it a stable idle? Can you feel the car idling rough or does it seem like it's pretty smooth

If you're not getting any other engines codes and do have a rough idle then yeah I would say to clean out your IACV. Replacing that knock sensor will make your car accelerate a lot better, it's just one 12mm bolt that holds it against the engine, a ratchet with an extension and a swivel socket will make the job easier. Use an OEM replacement I found one on eBay a year ago for around $25

 

The knock sensor code is there because something else is going on. It generally also goes away when that something has been fixed.

possible causes of missing or running rough are generally the coil, the spark plug, a valve cover leak, or a leaking fuel injector.

start by identifying which cylinder is running rough with a code reader or better yet, a scan guage. Both are cheap. I like the BASF scanner which is sold on amazon for 22 dollars. It will communicate with your smart phone. It will tell you which cyl has problems, or if it is running rich as flock.

chances are good that the coil on the suspect cyl is bad . Confirm that by trading the coil with the cyl next to it. If the problem follows the coil, you have a bad coil. If you notice that the coil is covered with oil, you have a bad valve cover gasket. Should the problem persist in the same original cyl, remove the spark plug. Smell it. If it smell's like gas, suspect bad fuel injector again, trase that plug with the cyl next to it. Should the problem still persist, suspect a leaking injector.

is you car hard to start, either when it has not been run for several hours , or on restart at the grocery store?

Do you have a white cloud exhaust when you start the car?

 

The car is not hard to start and pulls like hell. It does not miss or run rough. It usually idles at say 700 or 800 rpms and is now 400 or less and the tach bounces around.

 

Is your check engine light on?

We won't be able to help you much until you get a scanner like I mentioned, or at the very least, have your codes read.

 

I had the car in a shop last Friday afternoon, heading into a long weekend here in British Columbia.

The CEL was on and they read the codes. Only a knock sensor code which they turned on.

The idle was running rough, up and down and stalled on me a couple of time when I was set to leave.

I can't get the car in the shop until the 14th.

They thought it was the IACV and are going to check wiring and the IACV with a multimeter.

I had the car on the highway the other day.

It is a 5-speed with a Budget y-pipe and K&N panel filter and pulls as strong as ever.

 

Typo. They turned the CEL off.

 

Those symptoms could also be associated with a failing MAF or loose or broken MAF wire at the harness. I don't want to send you on a wild goose chase so rule in or out each component at a time, IACV, coils, spark plugs, etc.

 

I stopped by the shop yesterday. The mechanic I dealt with is on holidays this week. I will talk to him on Monday. Appointment is for Tuesday.

They mentioned that they will check the MAF. They also clean IAC valves. I mentioned they don't fail that often.

I don't believe it is a knock sensor issue given the way it pulls on the highway. I also don't believe it is a TPS or ECTS issue.

They commented on cleaning the throttle body which was done once before.

What would the symptoms be of a TB that needs cleaning?

 

The knock sensor generally show up along with another code, and goes away when the other code does. It seldom sets a code on its own.

I don't believe that the knock sensor is the cause of your problem.

if you have a smart phone, you should buy the BAFX scanner from amazon. It's only 22 dollars.
Once you have that, you can look up your own. Then you can let us know which code you have. Then we might be able to guide you through a repair.
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Thanks. It only showed a knock sensor code last Friday. No code for the IACV.

 

Hey J,

I've been thinking about something to diagnose my 99 Maxima and 99 Durango for a long time. Does this also give running diagnosis and running health type evaluations? What about ABS information?

Also, which APP did you download (since BAFX only makes the Interface) Are there differences in reading capabilities between the different APPs available? I have a stupidphone and in 2.5 years, I've never downloaded any APPs. I AM A FOSSIL! But my battery lasts 4 days. LOL Galaxy S6

Thank you as always in advance!

 

The BAFX scanner does show codes as well as live data. I've used it for codes, mpg, air/fuel ratio.

I'm having issues with my corolla. It's running rich as flock and spewing gas fumes. The scanner shows that the computer is leaning out the mixture to cope with that.
So the scanner shows if the ecu is adding or subractin fuel.

The scanner has most of the programs we need all on its own. I understand that there is an optional download available for 5 dollars.


​​​​​​It's possible that the scanner will also commuwith your laptop, I pad, or kindle. It communicate's with blue tooth or WI fi.

Look the scanner up on you tube or google.

mine was only 22 dollars. Some of the most worthwhile dollars I've ever spent.

 

Thanks Dawg! Sounds like a VERY intelligent investment at the peak of VALUE!

So, does that mean your Fuel Injectors are not delivering the optimal amount of gas and all the other systems are trying to over compensate to get it as right as possible?

 

JvG is correct. The knock sense code is a ghost code and only appear when other DTC's are logged. I as well agree it has nothing to do with your current symptoms. We have logged nearly 390k on our '97 SE, original IACV. Yes I have cleaned it several times in 21 years of ownership reusing the original metal gasket each time. Also you can retrieve your own DTC/CEL codes with a small flat bladed screwdriver, no need to wait or give someone $50 for that info. The code(s) are the key otherwise we are all guessing along with you. Just guessing I would say MAF, coil, leaking injector, or IATS. Its fuel delivery/management related.

 

Ordered it today! Gonna go for the most complete APP. $5 sounds GREAT! Thanks!

 

One last question before I take the car into the shop tomorrow. If a knock sensor requires replacement, will it result in a rough erratic idle and stalling when stopped?

I had to talk the mechanic out of changing the KS. It has thrown a code. No other code shown. The car pulls like crazy on the highway.

The only issue is the idle. I suspect the problem is that the IAC valve requires cleaning.

He wants to clean the IACV, throttle body and MAF. The problem that occurred was such that the idle was fine one day and not the next.

What are the symptoms of a throttle body requiring cleaning? Same with the MAF.

I question that all three need to be cleaned in my case.

I don't believe any parts need replacement.

Thanks

 

Coil packs don't always throw a code as they are going bad.

Fuel Injector Pintle caps can give up the ghost from one day to the other.

And then there's always vacuum leaks.

IMO, Less likely are the IACV and MAF and Throttle Body

 

All of these are simple repairs. Some cans of CRC throttle body spray, CRC maf cleaner, and carb spray for the iacv and some gaskets would cost perhaps 40-50 dollars. The spray cans would last for years.

 

I think I am going to start with cleaning the EGR tube. If that doesn't do the job, then the throttle body. I am going to stay away from the MAF if I can avoid it.

I cancelled the appointment I had today because of lack of confidence with them and their familiarity with the engine.

 

I would NOT start with the egr tube. Not unless you have an egr code. Of all the possible causes, the egrwould be both the least likely way to solve your issues and also the biggest pita. Don't forget that you need to buy 2 or 3 gaskets if you do go there anyway. Or you would create a massive vacuum leak.

The first thing I wold try is to clean the throttle body. It's likely that there are deposit's between the outside edges of the throttle plate and the throttle body. You could clean the tb either on the car, or you could remove it. The gasket is reusable unless it has been torn or messed up.

I cleaned mine with the throttle body spray a toothbrush, and paper towels.

The maf could be another cause of your issues.
There is no reason to fear cleaning it. Just spray the wire with CRC maf cleaner. Let it dry afterwards.
The spray will dissolve any crud which might be clinging to the wire.

So try these two things first, then see what happens.

If the problem persists after cleaning those, then the iacv is the next thing on the list.

While it's unlikely that all of these items are the cause of your issue, they are good general maintaince tasks which might help prevent problems from popping up sooner or later.

 

Thanks. I don't have an EGR code.

 

Old saying..... If it ain't broke, don't fix it.

Also, do the simple things first.

At the very least, you are methodicly eliminating possible problems. Just like he mechanic would, for far less money.

 

I just read something on the Internet where a Daniel B. Martin responded to someone on August 11 2001. This person was experiencing a low idle in a manual 1995 Maxima like mine and it would die when he pushed the clutch in.

Martin had some information from the FSM regarding a quick test for the IACV-AAC valve. He said to have the engine at normal operating temperature and at idle and switch the air conditioning from off to maximum and watch the tach. Idle speed should dip momentarily and recover. If the idle drops and does not recover, the engine may stumble, falter and stall. The IACV-AAC may require cleaning, adjustment or replacement.

When I did this the idle was absolutely stable at 500 rpms. When I turned the AC off the idle briefly popped up to say 700 and settled back down and actually idled better than before I turned the AC on, but not as well as when it was on.

I don't have any codes.

I am gong to start with cleaning of the throttle body properly. It has only been done once and that was by some kid at an oil change place where he just sprayed TB cleaner into it. That was when the car had 61,000 miles on it. It now has 110,700 miles on the clock.

 

It would run better at higher idle speed. Normal.

I'd say that the iacv is probably OK.

Open the throtitle by turning the lever which the thottle cable is attached to. Clean the edges of the throttle well. Also the throttle body at the points where the throttle plate would contact the throttle body if it were closed. Clean that too. That's where crud would interrupt air flow. Then clean the rest of the tb inside.

Spray the maf wire like I mentioned before. Allow that to evaporate for a while.

 

I got the problem resolved today. I took the car into a shop last week and it was showing a code for #3 cylinder misfire as well as knock sensor. The mechanic adjusted the idle.. The #3 cylinder misfire code went away. He switched the #3 ignition coil with the #1 to see if the problem would follow the coil. I was told to watch for a CEL.

My CEL came on on Saturday. I didn't drive the car on Sunday. I took the car into the shop first thing this morning. The problem didn't turn out to be a coil after all. The #3 cylinder misfire code reappeared.

The problem was traced to the #3 fuel injector which was replaced today. Idle reset. Good to go, except for the knock sensor code.

The car seems to run fine on the highway. No hesitation, no discernible loss of power which is what I was told I should experience.

I know there is a test that can be made to show whether the knock sensor is testing open circuit which means it requires replacement. The mechanic said it is open circuit but I am sure he didn't test it.

I am not sure what to do about the knock sensor.

 

we presume "#3 cylinder" means "the middle bore in the front", right? just so we're all on the same page
it would then of course follow that #3 coil was swapped into the #1 position for an effective test

since you have now seen what its like when one fuel injector fails, you will know what to look for when the other five start to do the same. the two remaining in the front are easy to swap out - the three in the rear require removing the UIM.

When you replace the fuel injectors in the rear - THAT'S the time to replace your knock sensor. And clean out the EGR guide tube. And service the valve cover gaskets, and the LIM gaskets and "all of that".

 

I had #5 replaced in the rear 35,000 kms ago. #3 replaced yesterday was in the rear. #5 only failed after using fuel injector cleaner and driving the vehicle up a steep hill. Something got dislodged in the injector.

Does anyone know if the knock sensor sub harness and pig tail are one and the same? I take it in order to have that part replaced the intake manifolds have to be removed to get access. Is that correct?

 

The knock sensor can be replaced without removing the uim. I have done this myself.
The​​​​​ knock sensors can be found cheaply on Amazon and Ebay. I bought mine for about 20 dollars. It's still working fine after several years.

Do a search on this forum for specific instructions regarding this proceedure.

In general terms, you are dealing with removing the sensor and the wire while it is in a long, tight tunnel with sharp edges. A 1/4 drive socket, some swivels, extentions with ball shaped ends which allow some movement are involved. Wrap masking tape around any joints to keep them from coming apart in use.

You should also have some stiff wire and tape to hold the new sensor in place while you turn the bolt a bit until it is seated. This is not comfortable, You might bleed. Small hands would be good. Ideally you would bribe a child to do this. Ideally a girl with delicate hands and long fingers.

 

does that mean that your mechanic is removing the fuel injectors in the rear bank (requiring removal of the UIM) and NOT replacing all three of them at once? OR offering to replace the Knock Sensor while its totally uncovered?

I replaced my KS without pulling the UIM (just like JvG) and you can too - but if you're taking the UIM off just for kicks then maybe you want to replace it next time you're in there.

 

The car can be driven without a functioning knock sensor. It won't have as much power as it should, and will probably have lower gas mileage. No point in using premium gas either. The timing advance is dialed back from where it could be by the ecu.

The car does perform better with a working knock sensor.

You could replace the knock sensor without removing the uim at this point.

Your other injectors will leak sooner or later. You might consider scheduling a time when you can live with taking the car out of service for a while so that you can do the other tasks which Reallywildstuff just mentioned.

Which would include replacing or rebuilding the rear injectors, replacing the rear valve cover gasket, the fuel line hoses and fuel filter, the egr tube and system, the coolant hoses back there, clean the throttle body and iacv valve. All these tasks can be performed fairly easily and at the same time if the uim is off. Yes, this is a royal fluster cluck. But once done, the car will run like new and be dependable.
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