Hi, I've started having an issue with my 2008 ranger, where the engine will shudder and die when stopping after ~15 minutes of driving.

I've replace the IAC, new spark plugs, plugin wires, fuel filter, air filter. Battery and alternator were replaced a few months ago. Changed the oil yesterday if that makes a difference.

It'll usually start up after a few minutes, have had it where it wouldn't start up after ~12 hours though.

The rpms also just started surging when I first turn it on, and it's idling. It feels like someone stomped on the gas, happens every time I turn it on.

2008 Sport 3.0 v6, 165K miles, no other problems.

 

Welcome to the forum

You need to use a Motorcraft or Hitachi brand IAC Valve on Fords, so if that's not what you got take it back, surging is actually a symptom of wrong IAC Valve brand
But can be caused by other things

Lets test the system the easy way
Cold engine, hasn't been run in last 6 hour
Do NOT touch the gas pedal
Start engine
It should surge to 1,500rpms, because IAC Valve is open all the way for start up(that happens with key on)
Then RPMs should drop to about 1,100, this is Choke Mode, all gasoline engines need to be choked on cold start
Over the next 3-8 minutes the idle should start to drop as engine warms up to 190degF, at that point idle should be about 800rpms if automatic, 750 in manual trans

Choke mode is the computer, ECT(engine coolant temp) sensor and IAC Valve all playing well together

If COLD start is not like this then there is a problem
Is the dash temp gauge working like it should?
Shows cold on cold start, then shows just below 1/2 after 5-8 minutes or so
In a 2008 the ECT sensor temp goes to computer and then computer sends it to the temp gauge on dash

Engine SHOULD surge to 1,500+rpms every time you start it up, thats the IAC Valve working, but if its not dropping fast after that then it might not be right brand of IAC Valve
When you turn the key on the computer boots up, it opens the IAC Valve all the way for start up, thats why it SHOULD surge and then drop

Clean MAF sensor, every year, its easy to do
Change or check PCV Valve and its hose, this can be a vacuum leak if something is wrong
PCV Valve should be changed every 3 oil changes

Stalling when stopping can be a few things, IAC Valve of course, but can be torque converter, but long shot
Try shifting to Neutral when coming to a stop, that will take the torque converter out of the mix if it continues to stall
Once that has been eliminated as possible problem then you can look at engine causes

Can't stress enough on the IAC Valve brand, people have chased there tails around for months because they used a 3rd party IAC Valves which is a hit and miss issue
3rd party are stepper/solenoid hybrids, Ford uses solenoid only, the stepper part is what causes the issues

 

Thanks for the reply Ron, here's what I've run into based off of some testing:

Startup RPM's: ~1700
Low idle: ~1000
After a few min: ~750

I took the MAF off and sprayed it a few times with MAF cleaner as it was dirty. After which the truck cranks but won't start at all. I thought I might have damaged the MAF when cleaning, so replaced that part (Hitachi is the brand of the new one) and rewired it as the wire insulation was cracked. New connector is Motorcraft. Without the MAF, the truck refuses to crank at all. Even with the new one, the truck cranks but won't turn on. I haven't heard the fuel pump priming when i turn the key, so that might be where I look next. Just surprised cleaning the MAF would cause an issue like this.

The new Motorcraft IAC arrives tomorrow, so I'll be replacing that but I'm think I've dug myself into a bigger hole here.

I have a code reader, but none are being thrown so I'm at a bit of a loss if it's not the pump.

 

Cleaning the MAF didn't cause this no start, MAF is not used when starting, no sensors are, except 1

Only sensor use for start up is the Crank sensor, not cam sensor, crank sensor, and they rarely fail
Turn on key, look for CEL(check engine light) being on, that means computer has booted up
Turn key to START, look at CEL, it should go OFF when engine is turning, that means Crank sensor is OK

Yes, no fuel would cause a No Start

50/50 test
Spray fuel into the engine
Gasoline, ether(quick start), even carb cleaner
Try to start engine
If it starts and then dies your spark and compression are good, but no fuel delivery
If it doesn't start then no spark or no compression
50/50 instant results

So don't waste your time "thinking" you know what it might be, just do the test and go from there

 

like your advice