So, I've got a 97 with the 2.3, and the check engine light is on, throwing a p1506 code. The code is idle air overspeed. I disconnected the battery and removed the IAC and cleaned it and nothing changed. Then with the truck running, I unplugged the IAC and the idle drops significantly, until I plug it back in at which point the idle speeds back up. Also when I ohmed it out I was getting about 9 ohms between the pins. Does that confirm the IAC is bad and needs replaced? Thanks!

 

If unplugging the IAC Valve.........with engine fully warmed up..............caused idle to drop then IAC Valve is OK

You don't mention idle RPMs, so I assume no tach
With engine warm, IAC Valve unplugged, engine should be barely running, stumbling
If not then you have a vacuum leak, so computer can't lower the RPMs enough with IAC Valve and set the code

 

Okay so I wasn't aware the engine needed to be at operating temp when you unplug the IAC. I did the test again, and unplugged the IAC with the engine at full operating temp, and there was no change in RPM. Does that mean the IAC needs replaced? Also that is correct I have no tach, and my OBD2 reader isn't working. Have a new one on the way so I can check what the revs actually are.

 

No it means you have a vacuum leak because of code p1506

The computer is closing the IAC Valve all the way, but RPMs are not dropping, so it sets that code
P1506 Idle Air Control Overspeed Error

Because it can't reduce the RPMs

You know IAC Valve is closed all the way because when you unplug its power is closes all the way, and your RPMs didn't drop
When engine was cold idle RPMs are higher, so when you unplugged it they did drop so you know IAC was open a bit and working


There is an Anti-diesel screw on the throttle linkage, some mistake it for an idle screw but fuel injected engines can't use an idle screw
Anyway, if someone adjusted it that may be your problem
Warm engine, at idle
Unplug IAC Valve
Turn that screw counter-clockwise, unscrew it, 1/2 turn, if idle starts to drop then keep turning until engine is barely running, you don't have a vacuum leak
If idle doesn't change then turn it 1/2 turn back to where it was, you have a vacuum leak

PCV Valve and hose is a good place to start with vacuum leak

 

Absolutely great info, thanks so much! I will start by adjusting that screw and go from there with whatever symptoms show. Thanks again and I'll let you know what happens!

 

Test for vacuum leak with engine warmed up and idling, and IAC Valve unplugged

Then pull a hose off the intake and plug its intake port with finger, see if RPMs drop
Repeat for next hose

 

You sir, are a scholar and a gentlemen! Got it fixed. While I was waiting for the truck to warm up I looked for any glaringly obvious vaccum leaks. Found a split hose but I'm not completely sure what it went to. It was down next to the battery, and it went into this little box with two half circle looking ***** on top lol not sure what it was. Anyway once the truck got to temp I unplugged the IAC, and turned the screw and the RPM dropped. Kept unscrewing it until engine was barely running, then plugged the IAC valve in and RPM came right up to what sounded like was perfect. Gonna have to use my new obd reader to check what the idle actually is. Gonna have to install a tac cuz I can't tell it's running now the idle is so quiet lol thanks again!

 

Good work

That vacuum line is running to the EVAP canister, it is used to suck air from the gas tank while you are driving, the sloshing fuel in the tank causes gas fumes which pollute the air so its an emissions system
There is a vacuum solenoid on that line so if the split is between that solenoid and the canister then it shouldn't cause a problem unless you are driving and even then it wouldn't be a bad problem

Tape it or repair it when you have time, no rush

 

I have a 2003 Ford Ranger 4x2, 3.0. 183,000. Was working fine until heat went out. Took to mechanic for a flush. No heat. Replaced thermostat. Not that. Then replaced radiator(?). Got heat. Got truck back, told idling rough. It was awful! Truck barely idling, CEL came on. Put a FIXD on it. Shows codes P2195,2197,P0147, says all cylynders misfiring( there 2 yrs old plug, wires, coil). Truck was fine until they worked on it. $512, later, and they will gladly fix their mistake if i pay. What should i do? Runs fine down highway. Smell gass when idling awhile. Well maintained. Ideas.

 

Welcome to the forum

You should start your own thread, this one is for 2.3l 4cyl engine, you have a V6, which matters

No heat in a 1995 thru 2011 Ranger means Blend Door Actuator failed, 99% of the time, its an electric motor in cab above glove box area, common failure on Fords in general

Bad thermostat "might" cause less heat in cab, never no heat, or it would cause overheating
Bad radiator just causes overheating never no heat

Not sure I would trust this mechanic or shop any more

Poor/rough idle wouldn't be IAC valve, High Idle maybe, which is what this thread was about

Poor/rough idle can be many things
Vacuum leak, small one can just effect idle, people/mechanics working in engine bay can accidentally separate vacuum hoses and not notice
Loose spark plug wires, same thing when people work in engine bay
Dirty MAF sensor, easy to clean

Dirty injectors, they drip fuel instead of spray it at idle, try Seafoam in gas tank

A little background on engine and O2 sensors naming
Bank 1 is passenger side of a V6 or V8 engine
Bank 2 is Drivers side

O2 sensor 1 is "upstream O2" closest to engine
O2 sensor 2 is "downstream O2" after Catalytic Converters
Rangers never had "O2 sensor 3's"


P0147 02 Sensor Heater Circuit Malfunction (Bank I Sensor 3)
Nonsense code, Rangers don't have "sensor 3's", BUT.........................
I have seen Rangers with an O2 sensor IN the Cat Converter and then another one after it, so could be sensor 2 and sensor 3, although I have never run across that designation on a Ranger
In any case that code usually mean one of the 4 wires at a downstream O2 sensor is damaged

P2195 O2 Sensor Signal Stuck Lean Bank 1 Sensor 1
P2197 O2 Sensor Signal Stuck Lean Bank 2 Sensor 1

If these are new codes, i.e. no CEL on until after the work on the truck
Then it looks like a Vacuum leak in upper intake, upper intake because it effect BOTH banks of the V6 engine

Just a heads up, O2 sensors are the only sensors that wear out, 12 years or 100k miles, so if you are not sure when they were last changed then change them, you MPG will be better for sure, may not fix the problem but 2003 with 180k should be on at least the 2nd set of upstream O2s