I am experiencing high idle RPMs in my Ford Ranger 2011 with a 2.3L engine and an automatic transmission. When the vehicle is in Parking Mode or Neutral, the idle RPMs fluctuate between 1500 to 2000 RPMs (rarely come close to the normal range of 1100).

In Drive mode, the idle RPM stabilizes at around 1100 RPM when the brake pedal is applied. However, releasing the brake pedal causes the truck to accelerate on its own, reaching speeds of 30-40+ mph while maintaining high RPMs (1500-2000+) without any input on the gas pedal. This situation makes driving uncomfortable, as I need to rely solely on the brakes to stop the truck. It feels like I'm simultaneously applying a slight amount of the gas pedal and the brake pedal. Only after a complete stop (at 0-5 mph) does the RPM return to 1100.

I've taken several steps to address this issue:
I've installed a brand new air filter, Throttle Position Sensor, Idle Air Control Valve. I've thoroughly cleaned the entire air intake system, including the MAF sensor and throttle body.
I've also fixed an exhaust leak located at the joint between the exhaust manifold and the next section of pipe, just before the first lambda reading sensor. Although I initially suspected that a gas leak might affect the RPMs due to lambda reading sensors, it appears that this was not the cause of the issue.


Any insights or suggestions from the community would be greatly appreciated. Thank you!

 

Welcome to the forum

I assume no CEL(check engine light)?

You have a vacuum/air leak

Basic gasoline engine, how it works
Gasoline engine has a throttle plate to control the amount of air coming into the engine, less air = lower RPM, more air = higher RPM, so that's how RPM is controlled

If you add more gasoline you get a flooded engine not higher RPM
So air flow is the key to RPMs on any/all gasoline engines

So even with your throttle closed all the way, too much air is coming in to the engine

Warm up the engine, shut it off
Remove the air intake tube from the intake
Unplug the IAC Valves 2 wire connector
Start engine
Use a gloved hand or piece of cardboard to partially cover throttle body's intake port, as its covered the RPM should start to drop, its just like a second throttle plate
Engine should stall if its completely covered because there is no air coming in
As air is restricted if there is a leak then you should start to hear it sucking in even more air as covering the throttle body opening will increase vacuum in the intake, a whistling sound

You can get a spray bottle and fill it with soapy water, spray it around the intake side of the idling engine, engine will stumble if the water is sucked in, and worse case, you end up with a cleaner engine, lol
I don't recommend spraying flammable fluids around a running engine because of the danger of fire