I recently purchased a 2001 Ranger with 4L V6. When started it would instantly rev to 2200 RPM then settle down, but during steady-state operation and at stop lights it would change idle speed approx 200 RPM. I was told to clean the idle motor on top of the throttle body, which I did, as well as clean the butterfly. Now it revs to 2000 RPM at start, settles down, then back to 2000 RPM. If I touch the gas it stays at 3000 RPM. If I unplug the idle motor it runs and idles fine, but the check engine light is on and the valve at the air filter box actuates when the idle valve is unplugged. Can I run it with the valve unplugged until I get it fixed? Which direction should I go to troubleshoot? Any ideas would be appreciated. Thanks.

Sledhaus

 

Disconnecting the IAC solenoid (it's not a motor) causes the vehicle to fall back onto a factory set default idle (a manual adjustment item). Your best bet is to find the problem and repair it at earliest convenience. I'd get my hands on a real man's shop manual (such as a Ford factory serviced manual or Alldata, not a stupid haynes or the like) and run pinpoint diagnostics on the IAC system. In fact, I'd be inclined to jump start the process by checking the resistance on the IAC solenoid itself.

 

Thanks for the info. Yes I have a collection of Haynes manuals for nearly every vehicle I've owned over the last 20 years and found them to be of limited use. I was trying to avoid buying one for this truck and doubted they would cover this type of problem anyway. I'd rather trust advice from experienced mechanics on a forum like this. Last resort is my Ford dealer and most independent shops are parts-changers so the costs can run higher than the dealer. I can change parts myself if that's the route I have to go. I first wanted to try some troubleshooting based on other's experiences. Thanks again.

 

If you want to check the IAC solenoids resistance as Bill suggested, with the engine & ignition switch off, disconnect it's electrical connector & probe with your multimeters + lead on the VPWR pin & the - lead on the IAC pin, resistance should be 6-10 ohms.

There is a diode in this circuit, so if you get your meters lead polarity reversed, you might read lower numbers.

Reset your multimeter to DC volts &
at KOEO you should have at least 10.5 volts DC, to ground, on the VPWR pin.

Let us know what you find.

 

i think it could be your idle control valve--that is what fixed mine and it is really simple to fix--it costs about 45.00

 

I agree. Usually its not the coil that gets screwed up on the iac, usually the plunger will get sticky, which makes the idle speed jump around. I'm on my 3rd one on my 03 4.0 at 81k miles. For some reason, they seem to like to get sticky.

You can confirm that this is the issue by cleaning the one you now have. Pull it off and spray carb cleaner into it until the junk running out is clear. Then, put it back on. Cleaning it usually will fix it for somewhere between a couple days to a month, so its not a long term fix, but it should tell you whether that's really it before you spend the $$ on it.

BTW, I've not been able to find the iac for the sohc anywhere except the dealer, so its more like $65.

 

Thanks to all respondents. I did remove it and clean it as instructed originally by a local mechanic and that's when it got worse. I just drove it 200 miles to work today with the IAC unplugged and it ran fine. No dying at stop lights or anything and idled smoothly at about 800 rpm. It started out with slight surging every 5 seconds on the second. Almost like it was beginning to starve for fuel or something but just barely. That stopped after a fuel miles and it ran fine. At one point when it began I stopped to plug in the IAC solenoid again but it again made it rev to 3000 rpm. I stopped at a Ford dealer on my way and they said the valve was special order at $75 because of different calibration codes. I plan to ohm out the valve and voltage check the circuit tonight and see if a local dealer around work will have one. I know better than to try to out-smart a computer so just hoping I didn't damage it by being stubborn. Can anybody educate me as to what the throttle position sensor does on the end of the throttle shaft? It was loose even though the mounting screws were bottomed in the throttle body housing as if it were missing a gasket or packing. I made a gasket to sandwich between them to tighten it up. It appeared to only sense extreme positions of the shaft with the allowable movement in it before the flat tip of the shaft would actually move the sensor. Any possible relationship to my problem?

 

I checked ohms on the IAC solenoid (9.4) and voltage at the plug. (Only millivolts with the key on and 14.2 with the engine running.) Any other suggestions? Plunger in valve seems to move freely with no sticking and seals good when you put your mouth on one chamber and blow.

 

That's the issue, when you blow through it you don't want a ton of air going through, that's what causes the high idle.

 

My troubleshooting results may have been misunderstood. When the solenoid valve is removed and in the spring-loaded closed position, you cannot blow air through it. It seals fine. So when installed and plugged back in voltage is opening it allowing air through which is causing the high idle. My questions are : is the voltage to the valve regulated to only open it slightly as needed or is it a full-open or full-closed only operated valve? So if it is working properly and is opening as it should, what other component regulates idle speed which could cause it to go to 3000 rpm and stay there ? Is there another sensor in the system controlling this that could affect it without setting off a code. Actually after driving it with the IAC valve unplugged the Check Eng light is staying on now even when I plug it back in. Does that mean it may now register a fault code that a shop can identify? Prior to that the light remained off.

 

Well the computer uses readings from the TPS (Throttle Position Sensor) to determine the position of the throttle plate & directs the IAC to move the throttle.

SO, if the TPS been replaced, removed, or it's adjustments otherwise messed with & reinstalled, without proper positioning, the computer could be confused about the proper throttle position & be telling the IAC to do things it shouldn't!!!!

 

We may be onto something now. Thanks Paw Paw. As I mentioned the TPS was loose like it was missing a gasket or packing. It most likely had been removed before and then I removed it to place a fabricated gasket behind it so it would remain tight when the screws are drawn up. I thought I put it back exactly were it was but that may not have been right either. How is it adjusted at reinstallation? Something didn't seem right because it had a big "bow-tie" looking slot in the sensor and the flat tip on the throttle shaft would have to move quite a bit to contact a surface either direction and move the sensor. Seemed to me the flat tip should fit in a straight slot or something so the sensor would know the exact position of the shaft. Please keep educating me Paw Paw.

 

Well I believe there is a tool used to postion the TPS. So maybe you could make loan of one, from your favorite autoparts store "loan-a-tool" program, for a refundable deposit.

 

I have 2001 ranger and 2.3 engine. I disconnected the IAC valve while the engine is running and the engine died.It ohmed out at 99 and from reading I thought when you disconnect the IAC that it would idle and not kill the engine.Any help would be great.

 

Welcome to FTE tugmanta.

The engine can run rough or stall when the IAC is disconnected.

99 ohms is high, according to my range in #4 post above .

Are you having idle problems????