Idle confusion

[masanders]

Had to go to Lowe's just now and pulled over to the side of the road. When I put my transmission in P it dropped 500(ish) RPM, struggled, then stalled. It started back up, struggled, and returned to normal RPM in D. Arrived at Lowe's and went inside. Came back out and started it up. Had NO idle issues. I just replaced the idle air control valve a couple months ago.

Not sure where to go on this one.

2006 Ranger XLT
4 cyl
AT

 

[RonD]

You will have to wait for a few repeats before even guessing could be done.

Why did you replace IAC Valve, what were the symptoms then?

 

[masanders]

You will have to wait for a few repeats before even guessing could be done.

Why did you replace IAC Valve, what were the symptoms then?

The RPMs had dropped by 250ish while driving and in park/neutral. It seemed to help until yesterday. I don't want to keep throwing money at it unless I know what's wrong.

 

[RonD]

Assuming you have a tablet or smartphone, I would spend the $20-$40 for a Bluetooth OBD2 reader.
These work on ANY car or truck sold in the US/Canada since 1996, so long term investment, assuming you will own more vehicles or know people who do

The APPS are free, or some are $5 and have a bit more information available, but start with free.

The IAC Valve is just a device, like a power door lock or power window, it doesn't do anything unless it is "told" to do it, in the case of door lock or window a button is pushed.
If door lock unlocks but doesn't lock then could be the lock itself or the button, the device or the control.

IAC valve is the same as the door lock, in its case the computer is the control(button)

Computer monitors RPMs, and computer has "target" RPMs, cold engine, warm engine, in gear, in Park/Neutral
Computer adjusts the Voltage to the IAC Valve to let in more air or less air to maintain Target RPMs, and it is very quick to adjust the RPMs.
And computer "learns", and remembers, what voltage will set what RPM

So even with small vacuum leaks computer will still hit the Target RPM set from the factory.

This is why I think you need the ODB2 reader, something isn't right, computer may be getting incorrect data, could be RPM data or "in gear" or Throttle position

Now if you got a 3rd party IAC Valve then it could be the problem, again, if the Ford IAC valve was the problem the first time.
IAC valve is a moving part so can, of course, fail, but 90% of sensors or electrics on an engine that are replaced were working just fine, thats a DIY stat, for Pro Mechanics its 50%, lol, but I think some of that is Bill Padding.

 

[masanders]

RonD...The CEL isn't on and I haven't been able to pull any codes on my Actron scanner. I have been looking into the BlueDriver Bluetooth obd tool. It's more than I want to pay, but it has live data. I'll update when I find anything out.

Thanks for your thoughts!

 

[RonD]

And just a thought, you should get your VIN and stop by a Ford Dealer service shop and have them check if you need any software updates.
Over the years there have been issues with high and low idles on various Ford engines/computers, which needed a software update to fix.

The updates are not free, but at least you will know not to spend money on non-fixes or temp fixes

 

[masanders]

As luck would have it the CEL went off today. Turns out it was the MAP sensor. Runs fairly well after changing it out.

I'll definitely check into the software.

 

[Ram Man 02]

I'm not sure if it makes a difference but when ever I replace any sensor I always pull the battery to drain the computer. that way when it relearns its with the new part. In theory the 2 parts should be identical but I'm never 100% so I makes me feel better knowing the computer has to relearn the new part.

 

[masanders]

I'm not sure if it makes a difference but when ever I replace any sensor I always pull the battery to drain the computer. that way when it relearns its with the new part. In theory the 2 parts should be identical but I'm never 100% so I makes me feel better knowing the computer has to relearn the new part.

Thanks Ram Man 02...definitely pulled the NEG cable. Made a big difference. Question about that though...does it have to be disconnected briefly (seconds) or longer?