Idle Air Control Valve?

[Brokenbone]

After its 2.3 liter engine is warmed up, our '87 Ranger has intermittent problems of idle dropping to nearly dying altogether and then overcompensating to recover. Normally, after throttling up to 1500rpm or so, it will idle steady for 15 or 20 seconds then start the process again.

After normal tuneup part replacements (i.e. plugs, wires, cap, rotor and fuel filters=there are 2), I spent over $100 on replacing O2, throttle position and EGR sensors but symptoms still occur. Was advised to consider replacing the Mass Air Flow sensor but that part doesn't exist for the '87 model. Was told the equivalent part is "Idle Air Control Valve" at approximately $80.

Anyone with a similar model have these kind of idle problems?
Was Idle Air Control Valve the solution or is there a better (hopefully more economical) answer?

Thanks for any feedback....
Brokenbone

[Stevo2]

The first thing I would do is to read the computer error codes. A cheap scanner for about $30 can be purchased at any auto parts store or Ebay or you can use a meter. This small investment has saved me hundreds of dollars in repairs. You could also pull off the idle air control valve and check/clean any sludge out of it. Should look something like this. http://www.partsamerica.com/product_...e/NIE21760.jpg

Wiring to same needs to be checked also for chaffing. Next be sure you clean out your throttle body in the area right behind the throttle plates. Pick up a can of special cleaner at the auto parts store. Hope this helps a little. Regards-Stevo

[Sidewalk]

Run the codes.

The IAC is absolutely nothing like the MAF sensor. The MAF measures the amount of air going into the engine and with the O2 sensor the computer changes the amount of the the injector is open.

The IAC is a solenoid valve only used for idle speed, nothing else. When the throttle is closed, and the engine reaches a low enough RPM, the computer will open the valve just enough to keep the engine at a steady RPM.

For these engine, the MAP sensor is most like a MAF sensor.

[Brokenbone]

Thanks to Stevo2 and Sidewalk for your input. I will check out these options.

Didn't consider the wiring going bad. Also, unfamiliar with MAP sensor and designed purpose of the IAC.

Have either of you used a voltage meter in place of the code scanners to diagnose problems? Read where an analog voltmeter may be a suitable substitute but doesn't seem like it would be reliable.

Thanks again for taking the time to respond to this thread

[Sidewalk]

Originally posted by Brokenbone
Thanks to Stevo2 and Sidewalk for your input. I will check out these options.

Didn't consider the wiring going bad. Also, unfamiliar with MAP sensor and designed purpose of the IAC.

Have either of you used a voltage meter in place of the code scanners to diagnose problems? Read where an analog voltmeter may be a suitable substitute but doesn't seem like it would be reliable.

Thanks again for taking the time to respond to this thread

MAP=Manifold Absolute Pressure. That sensor mesures the amount of vacuum (sometimes pressure) to get an idea of how much air is going through your engine. The computer compares that to the O2 sensor reading to inject the right amount of fuel. The exception is at idle and at around 70-80% throttle, where the computer follows it's pre programming.

The IAC is a solenoid valve, controlled by the computer, used to bypass air past the throttle body into the intake to allow the engine to idle. The throttle valve is completely closed during idle.

[Stevo2]

Has to be an analog meter(has needle to indicate reading or sweep) and NOT a digital meter. Analog(VOM) meters are dirt cheap. When using the meter all you are looking for are the pulses, the needle will move to the right every time it senses a voltage signal. This pulse would be the same thing you would see on a cheap scanner but on the scanner the light would blink. Read the codes several time to make sure you get them right...I always do. Be advised that not all engine problems will issue a code. Here's some links to look at. Good luck

http://www.therangerstation.com/OBD_I.html
http://www.actron.com/cgi-bin/web_st...e.htm&cart_id=

[Moodranger]

New here, but thought I would say something, and maybe get some help also. I have a 94 4.0 that is doing the EXACT same thing. I did clean out my intake stuff, and bought a brand new TPS, which did help some. I still have a slight problem in the mornings with it though. Also, it will die on me when I am slowing down, and I push the clutch in to put it in neutral. This is very disheartening because it will happen going 30 or 5 and then I lose steering control. If there is something I can do or any help you can give, please lend a hand.

David

[Stevo2]

Moodranger, on fuel injected engines anytime you are at idle or you let off the accelerator pedal to decelerate the throttle valve in the throttle body goes completely closed which means no air flow. The way they get around this is to use a Throttle Air Bypass Valve(goes by many different names) to allow a predetermined amount of air flow around the throttle valve which is determined by your computer. If this valve does not respond correctly then air flow may be too low and choke off the engine. just like having a stuck choke on a carb. The vehicle speed sensor also sends signals to the computer about acceleration and deceleration. You may want to check out/replace your bypass valve and see what happens. The very first thing I would do though is to make sure your engine is properly tuned and use a scanner to pull any error codes that are stored in the computer.

Bypass Valve :flash:

[Moodranger]

Actually that is what I did replace. Got a brand new one, and it helped out some, but it is still giving me trouble. It also will not open to full throttle when I floor the pedal. The only other thing suggested so far was that I might have a leak that is causing the problem.


Thanks for the help

[fordman123]

Moodranger,

Your problem may be due to an intake leaking (possibly)

To check for this start your engine and leave in park.
Get some carb cleaner and spray at the base of the intake plenum.
Also do the same for the vacuum lines.
If the engine picks up on RPM, sounds like you got a leak.

Just something I thought you might want to try.

Fordman123

[berryn]

Hey guys i'm having the same problem with my truck only i don't think it could be the throttle bypass valve with my problem. They rarly go and don't need replacing very often. My truck will stall at lower speeds when i put the clutch in but, if i give it throttle it will chugg and jerk and then after about fifteen seconds it will continue as if nothing is wrong. I sure would like to know if anybody has any ideas. I don't know if you are experiencing the same symptons. Oh ya i pulled the code and the eog sensors indicates sytem running lean, also the erg valve won't open code 33. I was wondering if it might be the map sensor.

[Stevo2]

berryn, we need to fix those codes first before moving on. The book says replace Oxygen sensor every 60K and if the sensor is giving false info to the computer that could cause air/fuel mixture problems. It may also be that the EGR valve circuit malfunction may be contributing to the O2 sensor code/failure. Lets try to get rid of those codes first. Did you clean out the manifold ports under the EGR valve when you replaced it? Was there any type of sensor attached to the top of the EGR valve? When you follow the vacuum line back from the EGR valve check to see if there are any small plastic connectors inline, if so this could be a restrictor or filter. Have you tried to disconnect the vacuum source to the EGR, plug the line and run the truck to see if any difference?
Couple more possibilities for the stalls/rough idle. The idle air bypass valve could still be sluggish, it must react instantly when you release your foot off the accelerator to provide more air flow as the throttle plate is now fully closed. It must also respond when you press the pedal down. Fords have a long history of sluggish air valves. Just some thoughts for later. Lets fix the other 2 codes first.:bandit:

[mankary]

my 94 ranger 2.3 liter
it will revs up by its self and i changed the iac and it still does the same thing....for the moment I disconected the plug and from the iac and it wont rev up but then in the mornings it does not idle hi to warm up....

need help...... thanks

[rantruck]

Q1) What is the difference between IAC or Idle air bypass. Are they two different components or two different names. If they are different where is the idle air bypass located. (I already know what IAC looks like and where it is located!)

I have a 94 ford Ranger V6-3.0; My Truck shows no power even when the pedal is depressed all the way to the floor. I replaced the Catalytic converter thinking it is a air flow problem. Also cleaned out the IAC thoroughly till it shined on the inside ports. When I step on the accelerator, while in park, the RPM gauge sluggishly reaches a max of 3800 RPM and upon releasing the accelerator the gauge sluggishly comes to idle of around 700RPM. I believe it is the same sluggishness that is reflected in the driveability. Can't seem to push past 4000RPM under load or in neutral. Seems to me the engine is struggling for air. Also under load I can feel a low frequency fluctuation in the engine power at the peak RPM (3800 RPM) judged by the sound. Is the ignition missing? Is there anything I can clean in the EGR valve or the pipe leading to it?

The problems described above gets worse when the engine is cold, leading to dangerously low power when merging into traffic. On a full tank of Gas I can get only 240 miles (~13-14miles) with city driving; is this normal?

I have installed new platinum plugs, wires, throttle position sensor, cap & rotor, EGR pressure differential sensor, air and fuel filter and a new catalytic converter. I have also cleaned the MAF, throttle body and fuel injectors with a gasoline additive.

There is no check engine sign! What else can I do to restore normal power?

[defaxxer]

I have a 2000 Mazda B3000 that is driving me insane. It is fuel-injected and has a manual transmission. Here's the problem: When I come out of generally first, second, or third gears while shifting up, I take my foot off the gas, push the clutch, and shift. Well, the problem is that after I push the clutch, the engine revvs up to around 3-4000 rpms and will stay there for around 3-4 seconds before dropping back down. If I shift into gear while this is happening, I can actually keep my foot off the gas and the car will continue to accelerate rapidly until the engine decides to stop revving. When I first noticed this problem, it normally only did it when the car was running cold, but now it just does it all the time. At these gas prices I can no longer sit by and watch this happen. I talked to a mechanic and he told me it was probably my IAC valve. I assume this is Idle Air Control Valve, or possibly my EGR, No idea what that means. I'm am an avid do-it-yourselfer and would like to know if this is something i can fix or if i have to be raped at the mechanic seven times before they actually fix the problem.