IACV Question - HIGH IDLE

[Peabody]

Hello, I have a 90 240sx and having idle probles like everyone else. I tried to clean the IACV but did not unplug the sensors because someone posted that it is hard because of the staples and to practice on one before you take the ones off the car. I have no idea how to take the plugs with the staples off and do not have one to practive on. So I just cleaned what I could with it still connected and holding it in one hand. It did not have that much mess in it. I did not take the brass screw out so maybe that is where the problem is. Problem is when I come to a stop the idle goes down to 500 RPM and then about every few seconds goes up around 100 RPM's until it reaches 1500 RPM's and then stays there. Will not go down until I take off press in the clutch and it goes to 500 and then raises to 1500. I know people have cleaned/replaced the IACV and that helped the low idle when at a stop but mine goes up and up and will not come down. So should I clean the IACV with it off the car? Does the IACV make the idle riase to a high level? I checked for vacuum leaks and do not have any. I had this same problem months ago and it just went away. I always clean my throttle body and use Sea Foam for carbon deposits. THANKS FOR ANY HELP!

[MagikDragon]

I'm actually having the exact same issues. Exact. If anyone can help that would be awesome, I've pulled my hair out looking for a solution.

[vancouverbc]

pic of staple. you could just snip the staple because the plug works without the staple. the staple just locks in the connection. just be careful .

cleaning the iacv helped with my high idle but 1500 is high. make sure the aiv hose to filter is disconnected. you could have a problem with tps.

Your air regulator might be stuck open. it should only be open for a few minutes when car starts. squeeze the hose going to air regulator when car is warmed up. if idle goes down , you know the problem is the air regulator.

see the thread in my signature for stalling for a pic of air regulator. the hose is a bit hard to reach through intake manifold but not that hard.

[vancouverbc]

the pic shows the air regulator with manifold removed. follow the yellow arrow that start at "air regulator" label. the arrow ends at the black rubber hose you should squeeze. use rag and large pliers.

[Peabody]

Ok I got the IACV off the car without any problems. Was not dirty at all. I took the brass fitting and cleaned the plunger and spring and also the other plunger and spring off the ACC (ACC might be called something else) I am talking about the thing that is held on with 2 screws. But it back on car with EGR and BPT and the idle did go down after warm up to around 900 RPM's. Turning the idle screw in all the way does not make it go down so I just backed it out untill it started to go higher. No more steady climbing to 1500 but the idle is all over the place. It will jump down from 900 then jump to 1200 then back and forth real fast, not like it was at a stop slowly climbing to 1500 and then just staying at 1500. I will squeeze the hose going to air regulator tomorrow and see what that does.anything else I can try? I am the original owner of the car with 150,000 miles. I would always change the oil, plugs, filters, ETC and did not dog out the car. Not saying I did not have fun on the streets racing every now and then but I did not abuse the car.THANKS AGAIN!

[vancouverbc]

the tps has to be disconnected when you adjust idle. it is likely that there are multiple things wrong with idle.

the brass screw on the iacv unit may come loose with epoxy off. i used a dab of silicone to keep it in place. try to leave the brass screw in original position. if nothing else works, than adjust it.

the easiest thing to do, is to disconnect the hose from the aiv unit going to filter. The aiv unit is genuinely useless so it is a good idea to disconnect this hose. Otherwise, when the reed valve goes , you get exhaust and water going into your filter area which is where the maf is.

you should also clean the throttle body and plate. a tooth brush and carb cleaner should work.

My aiv is disconnected. If I connect it back up, my idle goes nuts. My car is a 1991 and the aiv was totally rusted out.

[Peabody]

Hey vancouverbc, Thanks for your pics and help. I forgot to say that my AIV has been out of the car for years. I would clean it every few months and the car would run great so I viewed many posts saying it is a good idea to just remove it. I have cleaned the throttle body using cleaner through a vacuum hose on the side of the TB and just spray it in and when the engine starts to kill just give it more gas to keep it running and keep spraying more in until I am out of the TB cleaner. Is this not a good way to clean the TB? Maybe I need to get inside the TB with a toothbrush like you said. I would use the cleaner almost every 2 to 3 months through a vacuum hose going to the front of the TB but maybe it is really dirty and I just never looked inside. To disconnect TPS is that the other plug on the IACV side? Not the one on the brass screw or is it somewhere else? Thanks again, I live in New Orleans and dealing with Katrina is very stressfull. My S13 and I also have an original 67 GTO I got from the original owner 14 years ago were parked in a garage and did not get any flood damage. Any other suggestions?

[vancouverbc]

I found this article in article section. It explains the procedure for adjusting idle. Definitely clean the throttle with toothbrush. The spring on iacv might be weakened but I doubt it. You just tighten the brass screw to correct.The TPS plug is at front of engine by the the throttle body. It plugs into throttle body. You can also adjust the tps which changes the idle.

"If your engine continues to idle real high after it's warmed up, check the air regulator unit. It's located on the passenger side of the engine, below the intake manifold, near the rear. There's a hose connecting to it. Pinch the hose when you are having the high idle condition. If the idle speed drops, there's a problem with the unit. Also check the electrical ground connections on the engine for looseness and oxidation.Another thing to check for is an air intake leak somewhere along the intake plenum between the Air Flow Meter and the Throttle Valve. Check all the nuts for tightness that fasten the intake system to the engine.

Adjusting the idle is pretty straight forward:

Disconnect the TPS harness and turn the idle adj. screw on the IAA to get the car to idle at 650 rpm. Reconnect the TPS harness and your beloved should purr at 700 or so rpm. (The Factory manual gives a +/- tolerance of 50 rpm.) The IAA is at the back of the intake manifold. You can see it standing over the right (passenger side for N.A.) fender and looking at the funky device with the dime size recess for the adj. screw.

Contributed by: RogoMan"

[Peabody]

I will check out the air regulator tomorrow. That is one thing I did not get to. I am sure I can find it. Another thing is when I took off the IACV the brass screw was all the way in and very hard to take off. Could that be a problem? Does the position of the brass screw have any effect on the idle?

THANKS AGAIN

[vancouverbc]

Did you have to remove epoxy off the brass screw? You cant do anything iwth screw until epoxy is removed and that is a big job. I guess they may not have put epoxy on for the 1990. It definitely should not have been screwed all the way in. Once the epoxy is off, it screws and unscrews very easily. It affects the idle very profoundly. It was strange that your aac was clean. If there is no expoxy on brass screw, you could have just unscrewed the screw and pulled out piston and spring to clean.
Modified by vancouverbc at 1:56 PM 10/15/2006

[Peabody]

No epoxy on the screw at all and I mean it was on so tight I had to hold it with a vise grip and use a wrench to get it off. I do most of the work on my car but have had my cooling system flushed the correct way and maybe someone saw that it was on not on tight and did not know they should not fool with it and screwed it in all the way.

The build date on my car is 4/90.

Should I try to turn it back and see if I can get the idle to go down? What a funny way to set the idle, but if it works and does not mess with the ecu that is fine with me.THANKS

[vancouverbc]

I think loosening it raises the idle. Not sure. Someone may have screwed it in in an attempt to lower a high idle.

If you look at the pic of mine it has remnants of epoxy and is all beaten up by the process of removing epoxy.

When your car is moving it is getting lots of air through radiator, so it has an easy time staying cool. When you stop, it becomes very hard to stay cool. The water pump etc has to work harder putting stress on battery and alternator etc. The alternator has 3 circuits so if you lose a diode it only works at 67% capacity. the gears dont have anything to do with the idle.The temperature sensor has input on what the idle should be. If you had a high idle while coasting, that would suggest a malfunctioning temp sensor but it makes sense that idle should go up when you are stopped.

[Peabody]

OH God - I really feel like a total idiot now.

The screw I was talking about was the brass fitting that has the sensor plug on it and not the screw I now see in your picture. For some reason I do not remember it on the IACV. Maybe I was not looking for it because I thought the big brass fitting was the so called screw.

That might be my problem because I did not even mess with the correct screw. I am going to find the post on cleaning the IACV and start over and I hope that corrects my problem.

THANKS!

[Peabody]

I understand what you are saying about cooling system, alternator, ETC. But it just seems strange that over and over the idle is low when I am not in gear just moving and the second I come to a complete stop the idle will climb higher and higher. I do not see how a few seconds of stopping would cause the alternator and cooling system to raise the idle. Sure I understand if I am just sitting for some time but I have done this over and over and after maybe 2 seconds the crazy Idle just climbs to 1250.

I just went outside to look for that brass screw on the IACV and I could not find it. When I had it off the car I did not see any screws (only on the solenoid) and I saw the large fitting so I just thought it was the screw. I did take the solenoid off with 2 screws and a plunger and spring came out. Could that take the place of the correct screw?

I went to AutoZone just to see their price on a new ICV and they told me that two company's made the valve they had a picture of the two and said I would have to bring my old one in to match it up so they could order the correct one. Could I have a ACV that did not come with the screw?

I just took a quick look at he ACV on the car and did not see the screw. I will take it off the car again and check for the screw. If I do not find it then I will take a picture and post it. For some wild reason mine does not have the screw do you think I should replace it?

THANKS AGAIN FOR ALL YOUR GREAT HELP!

[vancouverbc]

The brass screw is covered in epoxy. With a flashlight(mirror helps) you can see it with iacv on the car. When you take the brass screw off. there is a spring that comes out. There is also a black plastic piston that is about two inches long. This black piston will be caked with carbon debris.

As far as temperature, there is a dramatic difference between a stationary and moving car. One scenario is that the IACV is working very well. It is raising the idle to compensate for a weak battery, alternator, water pump, etc.

Disconnect your o2 sensor to see if that improves it.

[Peabody]

OK - I understand now about the car moving. Well I just replaced my water pump 2 weeks ago, my battery is about 2 years old and I replaced the alternator in 2000 so it would not be a bad idea to check out the charging system before I mess with that crazy screw. The rest of the IACV was very clean maybe because I clean my throttle body every time I change my oil and change my plugs, rotor, wires every year to keep the engine running it tip top shape. I am the original owner and never had any idle problems so that is why I am so concerned about fixing the problem ASAP.

Thank you vancouverbc for all your replys and I hope to get to the bottom of this problem. I might see what a used IACV costs at a yard and connect it instead of messing with the epoxy. I have a felling once I get the screw out it will be clean like all the other pieces in the IACV.

I have another post about timing and I checked it today with a light and it was off the scale. I would say if another scale was added it would be at the end of that also. Maybe 40 degrees instead of the stock 20. When I turned it down the idle did drop down to 800 so that might have been the problem. I did not drive the car to see if it lost power due to the big change in timing. I run 93 octaine and did not hear any pinging so the high timing might be OK. Have over 150,000 miles and have had no major problems. If I can tell a big loss in power should I bring it back to where it was. I know it has been in the same position for 16 years from the markings on the bolts, ETC.

THANKS FOR ALL THE GREAT HELP!

[Madmax3]

I also have a 90 with the same problem. There is not a brass screw on mine. It is silver and located on the passenger side of the intake kind of under a bracket the the fuel lines connect to.

Peabody,Did you ever find out what the problem was?

[Peabody]

Hi, Well yes and no. I did the tests on the TPS and mine tested close to the numbers on the test but were a little off like I had 7 K Ohms at full throttle instead of 10 K. You also have to adjust the TPS with a voltmeter by rotating the Throttle Sensor body so that the output voltage is 0.45 - 0.55. When I do that the idle stays at 1500 RPM's and will not go down. So I just started to turn the TPS to the left about .32 volts and I got my idle to go down to 800 RPM's and it runs fine. I am not sure if setting the TPS voltage lower is a bad thing to do but it helped my problem and I have no problems with a high idle anymore. I got another TPS from a yard and it acted the same way so I do not know if that one was bad or if there is another problem. I just but my old one back on and adjusted it and got my idle back to 800 RPM's and checked the voltage and it was at .32 and any higher would make the idle jump from 800 to 1500 until I turned it back to .32 volts and the idle went back to 800 RPMS. It also goes up to 1000 RPM's when I turn on the AC so I know the IACV is working. HOPE THIS HELPS!

[Madmax3]

Thanks, I will look at the TPS tomorrow. I actually got it to idle today at about 750 until it warmed up and then it went to 2300.

[Peabody]

That is what my did. I forgot to say it was fine until it warmed up and then 1500 RPM's everytime I would stop. I am glad well not glad but I do not think the people understood what I way saying when I came to a complete stop the idle shot up.GOOD LUCK!

[g35paul]

yeah my 92 240 has sat for bout 2 years and finally now i been driving it and man do i have a high idle.... mine stays at bout 1500 and runs up to bout 2300..every now and then i can hit the gas and get it to go down to 1200 but it slowly climbs.... ill have to try some of this tomorrow

[mick]

I will check out the air regulator tomorrow. That is one thing I did not get to. I am sure I can find it. Another thing is when I took off the IACV the brass screw was all the way in and very hard to take off. Could that be a problem? Does the position of the brass screw have any effect on the idle?

THANKS AGAIN

Where is the Air Regulator?

[vancouverbc]

Where is the Air Regulator?

zer...r.jpg

[vancouverbc]

Where is the Air Regulator?

here it is on sohc

http://img265.imageshack.us/my...z.jpg

[vancouverbc]

look up air regulator in tutorials for more info

[mick]

You mean the IACV on the left is the air regulator?

[vancouverbc]

the

You mean the IACV on the left is the air regulator?

the air regulator is circled in yellow. find it in the sohc picture

[s13mike91]

it sounds like a vacumn leak. mine did something similar and one of the vacumn hoses going to the throttle body broke.

[mick]

here it is on sohc

http://img265.imageshack.us/my...z.jpg

I found it.

How do you measure the TPS voltage & resistance? Which wires?
Modified by mick at 2:04 PM 4/19/2009