Stalling

[Buckeyeman]

I have a 2010 Ranger w/2.3L 5-speed and when I come to a stoplight and push in the clutch, the rpm on the tach drops to 500 sometimes below and stalls. This is a intermittent problem. The truck runs smooth and idles smooth other wise. I've been watching the tach coming to a stop and most of the time the rpm's will drop to 500 then the ECU raises it to around 925-950 and it idles fine. Could the clutch switch be going bad? What is causing the rpm's to drop so low until the ECU bumps them back up?

Thanks for anyone's help.

 

[RonD]

I would first clean the IAC(idle air control) valve, computer uses this to set idle RPMs.

IAC uses a Step Motor(stepper motor), this is a "digital controlled" electric motor.
Step motor will have over 100 "steps" the computer can "call up", each step represents a degree of turning of the motor
Step 10 might turn motor from "start" to 90deg(1/4 turn)
Step 50 might turn motor from "start" to 450deg(1 and 1/4 turn)
Steps are "called" using voltage pulses from computer to IAC Valve, like a Morse Code.
The IAC valve is a "learned" control, the computer "learns" what Step is 650rpm on warm engine, and what Step is 1,000rpm on cold engine.
The computer has "target" RPMs in memory, these are related to engine temp.
My 4.0l Manual trans has "target" idle of 625rpm warm, when last checked it was 623 to 628rpm, so very precise.
On my 4.0l 628 rpms might be Step 20, one another 4.0l it might be Step 19 or Step 21, computer "learns" and remembers what Step to use to get "target", and this "learning" is on going

The IAC valve is pushed and pulled, closed and open by the motor turning.
If valve should get sticky it may not be closing enough so computer calls a Lower Step to force it closed more and idle drops down to low, and before computer can raise it back up engine stalls or opening IAC valve a little more doesn't help because it is sticking again so computer calls higher Step and RPMs run up too high.
And as computer "learns" new Steps they change again when valve sticks, lol, so intermittent issues.

4cyl does idle slightly higher than V6/V8, I would expect warm engine idle for manual trans 2.3l to be 700-750, automatic 750-800
I think 925-950 is too high for warmed up engine with manual trans, but never had a 2.3l Duratec engine.

 

[adsm08]

If you have an IAC issue you should get ahold of the dealer, unless you have a ton of miles. That part may well be covered by the powertrain warranty.

 

[Buckeyeman]

If you have an IAC issue you should get a hold of the dealer, unless you have a ton of miles. That part may well be covered by the powertrain warranty.

I have 53K on truck, plus I have the Ford Premium Care Extended Service Plan.

Thanks

 

[Buckeyeman]

I would first clean the IAC(idle air control) valve, computer uses this to set idle RPMs.

IAC uses a Step Motor(stepper motor), this is a "digital controlled" electric motor.
Step motor will have over 100 "steps" the computer can "call up", each step represents a degree of turning of the motor
Step 10 might turn motor from "start" to 90deg(1/4 turn)
Step 50 might turn motor from "start" to 450deg(1 and 1/4 turn)
Steps are "called" using voltage pulses from computer to IAC Valve, like a Morse Code.
The IAC valve is a "learned" control, the computer "learns" what Step is 650rpm on warm engine, and what Step is 1,000rpm on cold engine.
The computer has "target" RPMs in memory, these are related to engine temp.
My 4.0l Manual trans has "target" idle of 625rpm warm, when last checked it was 623 to 628rpm, so very precise.
On my 4.0l 628 rpms might be Step 20, one another 4.0l it might be Step 19 or Step 21, computer "learns" and remembers what Step to use to get "target", and this "learning" is on going

The IAC valve is pushed and pulled, closed and open by the motor turning.
If valve should get sticky it may not be closing enough so computer calls a Lower Step to force it closed more and idle drops down to low, and before computer can raise it back up engine stalls or opening IAC valve a little more doesn't help because it is sticking again so computer calls higher Step and RPMs run up too high.
And as computer "learns" new Steps they change again when valve sticks, lol, so intermittent issues.

4cyl does idle slightly higher than V6/V8, I would expect warm engine idle for manual trans 2.3l to be 700-750, automatic 750-800
I think 925-950 is too high for warmed up engine with manual trans, but never had a 2.3l Duratec engine.

Thanks for the detailed explanation.

As far as the idle rpm's, I don't know how accurate the factory tach is, but looks in the 925-950 range.

 

[enjr44]

Just an FYI, if engine rpm drops below 400, for safety reasons, the computer shuts off the fuel pump.

 

[Buckeyeman]

I called the dealer to see if it was covered under warranty, and the service writer said she would have to get the p/n and run the vin to see if it covered. It's been 2 days and no call back, so I took it off and cleaned it with CRC Mass Air Flow Sensor cleaner. Well now all I have to do is wait and see if that takes care it.

Thanks

 

[enjr44]

The IAC is listed as part of the emissions control system so it should be covered the the Federally mandated emissions warranty. I fact most anything that can cause stalling would be covered. I think that is good for at least 8 years or 80K miles. You need to take control the of the problem ---- dealer will not come to you!!!

http://www.fordparts.com/Commerce/CatalogResults.aspx?y=2009&m=Ford&mo=Ranger#Search

 

[Buckeyeman]

After cleaning the IAC valve, and replacing the fuel filter it hasn't stalled. So far so good. I hope this takes care of it.

 

[Buckeyeman]

It seems now I'm going to have to replace the IAC valve. It still hasn't stalled since I cleaned it. I've been experiencing hard starting when warm. What is the difference in quality between the Motorcraft part and an aftermarket? The Motorcraft is three times the price of an aftermarket.

 

[RonD]

IAC Valve uses a Step motor, or Stepper motor, this is in essence a digital motor that gets Pulsed electrical commands from the computer.
Like a Morse Code electrical pulse.
Computer will have over 100 "step commands" it can send to the IAC Valve motor, each step is a degree of rotation from 0
Step 1 = rotate to 2 degree from 0
Step 2 = rotate to 4 degree from 0
ect.....

As the motor rotates the valve closes or opens.
Computer "learns" what "Steps" it needs to use to get the different idle RPMs for the engine.
This is why if you reset the computer or install a new IAC Valve it will take a few drive cycles for computer to "reLearn" the Steps needed, so idle may wander a bit at this time.

IAC Valve don't fail that often, but are often replaced, lol.
90% of sensors or controls replaced by DIYers were not bad, just seems simpler for most to replace things.
But don't feel to bad, 50% of sensors or controls replaced by Pro Mechanics were not bad, although "bill padding" would be part of that not just lack of testing.

I would probably get a Ford IAC Valve from wrecking yard before a 3rd party IAC Valve, as said they don't fail that often so pretty safe bet on late model used one.

If possible pull off IAC Valve and connect it to it's wires, have someone turn on the key while you watch the valve, it should open all the way for starting, then unplug the wires and it should close again

 

[enjr44]

You said it was a 2010 with around 50K on it. Federal law requires a 75K and 8 or 10 years warranty. Google it!!!

So unless you just like messing with it, take it in. Don't ask them, tell them its broke.

 

[Buckeyeman]

You said it was a 2010 with around 50K on it. Federal law requires a 75K and 8 or 10 years warranty. Google it!!!

So unless you just like messing with it, take it in. Don't ask them, tell them its broke.

I did take it in to the dealer, and they told me it wasn't covered.

 

[Buckeyeman]

After replacing the IAC valve with a B/W unit in 4/16 the truck seems to doing the same thing now. The rpm's are fluctuating at a stop light, sometimes stalling. This is an intermittent problem. The truck has 64K on it now. Is there anything else it could be?

Thanks.

 

[Ram Man 02]

Sounds like the IAC again. My taurus has had the same symptoms. I just clean it and its fine for a few years. Im not sure where the IAC is on the ranger because the truck is new to me but If you have a rubber mallet and can get to it easily give it a couple taps. That can free up the piston but cleaning is the best answer.