My car idles rough when stopped

My truck is idleing really rough only when stopped. It wants to die if stopped to long I changed the idle control valve and all 6 coils but it didn't help

My car has 187000 miles.
My car has an automatic transmission.

Experienced mechanics share their insights in answering this question :
This may be a sign of a leaky injector or potentially an incorrect idle air adjustment. A leaky injector can cause a rich fuel condition as it may leak too much fuel into a cylinder not allowing the combustion cycle to burn the fuel evenly resulting in excess unburnt fuel being unused and momentarily flooding the motor causing this kind of rough idle. When this happens, you may notice a bit of black smoke coming from the exhaust as well as a slight fuel smell.

This may also be a slightly misadjusted throttle plate. The throttle plate is adjusted at a specific angle to allow just the right amount of air into the throttle body at idle speeds. This is done by the work of an actuator motor that electronically adjusts this. When this is not working properly, this may cause a rough idle due to an unbalanced load of air and fuel to be supplied to the motor.

To avoid any unnecessary repairs, I would recommend having an expert from YourMechanic come to your location to diagnose your rough idle firsthand.

How to Identify and Fix Common car Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced mechanics :

Common culprits include the ignition control module, plug wires, coils, and spark plugs. Defective Airflow Sensor: A defective airflow sensor can be responsible for a rough idle.
The most common reasons a Ford Escape has rough idle are a vacuum leak, an issue with the spark plugs, or a problem with the ignition coil.
Causes of a rough idle. Many different problems could result in a rough idle for your car or truck, including: dirty fuel injectors, clogged air filters, bad spark plugs, and a variety of exhaust system issues.
A rough idling engine can be caused by spark plugs or spark plug wires. Spark plugs use the electrical current received from ignition coils to ignite the air/fuel mixture within the combustion chamber. A plug that is damaged or installed incorrectly can result in fuel being burned at an inconsistent rate.
Oxygen (O2) sensor

An oxygen sensor monitors and analyzes the amount of oxygen in a vehicle`s exhaust system after combustion. A dirty, damaged or malfunctioning O2 sensor (or sensors) affects the air/fuel mixture, causing the engine to idle rough.

Engine hunting and surging at idle is usually caused by a fuel delivery, air leak, or governor system problem. Cleaning/overhauling the carburettor, adjustment of the governor, and/or changing the air filer may be required.
The Ignition System

The shaking occurs as your truck`s engine struggles to remain running while at idle. A few common causes within the ignition system are: Engine Misfires. Faulty Spark Plugs.

Fuel injector nozzles can become clogged over time, which can lead to a sputtering engine, slow acceleration and the car not having enough power. Fuel injectors can be cleaned if the problem is caught early, but as the conditions worsens, the injectors may have to be replaced.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

My car has a rough idle when I start my car, when I stop at a light my car turns off. Is it the purge sensor?
ANSWER : This may be a result of a dirty or failing idle air control valve. The idle air control valve reads the air intake as it is mixed with fuel prior to being injected into the engine at low speeds and at idle. Since this valve is controlled by the vehicle’s computer, it will adjust idle speed based upon other measurements such as engine temperature, intake air temperature and electrical system load or voltage. When you accelerate, the engine RPM increases, and as you let off the gas, the RPM slowly returns to the normal idling speed with the help of the idle air control valve making the transition from a higher RPM back down to idle speed. When the engine RPM drops below the normal range of about ~800 RPM, this often times will cause the engine to stall indicating a dirty or faulty idle air control valve. I would recommend having an expert from YourMechanic come to your location to diagnose and repair your idle air control valve.

My car is idling very rough.
ANSWER : The idle air control valve is common for causing a rough idle in many cars, but it sounds like you have already corrected that. Another thing you may also want to check is the crankshaft position sensor. A crankshaft position sensor monitors the position or rotational speed of the crankshaft. This information is used by engine management systems to control the fuel injection or the ignition system timing and other engine parameters. When this is faulty or not working properly, this will cause problems with the ignition system and generating spark transmission to the spark plugs resulting in starting problems, rough idling and other performance issues. You may also want to check the fuel pressure as low fuel pressure can also cause rough or poor idling if the fuel pattern being sprayed from the injectors is not consistent. This can also happen in the case of having dirty fuel injectors which may also interrupt the spray pattern of the injectors. I would recommend having an expert from YourMechanic come to your location to diagnose and inspect your car.

When I stop at the stop light or a stop sign my car shuts off.
ANSWER : It sounds like you may have a dirty or failing idle air control valve. The idle air control valve monitors the air intake as it is mixed with fuel prior to being injected into the engine at low speeds and at idle. This valve is controlled by the vehicle’s computer and will adjust idle speed based upon other measurements such as engine temperature, intake air temperature and electrical system load or voltage. This is also an important function when starting the motor as it allows the motor to run and idle on it’s own once the motor fires. When you accelerate, the engine RPM increases, and as you let off the gas, the RPM slowly returns to the normal idling speed with the help of the idle air control valve making the transition from a higher RPM back down to idle speed while adjusting the air/fuel ratio constantly to allow this to happen smoothly. When the engine RPM drops below the normal range of about ~800 RPM, this often times will cause the engine to stall indicating a dirty or faulty idle air control valve. I would recommend having an expert from YourMechanic come to your location to diagnose and inspect your vehicle.

Why does my Echo rough idles at a red light or stop sign?
ANSWER : Hello,
What you are describing is a common sign of a dirty or faulty idle control valve. The idle air control valve is a small valve on the engine’s intake system that reads the air intake as it comes into the motor. This is controlled by the car’s ECM which uses this information to make adjustments to the air/fuel ratio depending on various inputs such as outside air temperature, intake air temperature, load and various other things. As you accelerate, your car’s engine is receiving a much higher dose of fuel than when at idle and conversely, when you let off the gas pedal, there is a sudden change in this fuel supply as a result of your foot letting off the pedal. When this happens, the job of the idle air control valve is to bring this deceleration down to a slow and smooth idle rather than suddenly cutting off the fuel supply causing the motor to die. When the idle air control valve is not working properly, this cause a disruption in this process resulting in the engine not being able to idle properly. I would recommend having a professional come to your location to diagnose and inspect your vehicle.

My car started idleing rough, vibrations soon as start car, vibrations soon as I accelerate, vibrations, rough idle bad
ANSWER : This sound like you may be having an engine misfire. Have the system checked and scanned to see if codes are present for an engine misfire. If it is, then a mechanic can check to see if a coil or spark plug has failed. You may have oil leaks in the valve cover seals that has caused the ignition to short out in the spark plug holes. A repair of your valve cover gaskets may be necessary, along with the other components that I’ve mentioned. I’d recommend having the vehicle looked at by a qualified technician who will be able to diagnose these misfiring symptoms and fix it accordingly.

My car runs rough at idle, stalls at idle, surges, and idles at 40 miles an hour
ANSWER : A number of components or faults can cause your issues. A vacuum leak can cause your issues. Depending on the vehicle, components such as the mass airflow sensor, throttle position sensor, coolant temperature sensor, and a number of others can be the cause. Since randomly replacing parts can get expensive as most electronic components are not returnable once installed, having a certified technician, such as one from YourMechanic, diagnose the stalling/surging is the best place to start.

Got my rear main seal fixed, but my car keeps having a rough idle, cutting off & the Electronic Throttle Control Light is on.
ANSWER : It sounds like you may have a faulty electronic throttle control unit. The electronic throttle unit opens and closes the throttle blade based upon input from various engine control sensors, including the accelerator pedal. This unit also controls, among other things, the cruise control function as well. When this control unit fails, this may cause intermittent stalling issues and rough idle problems. This is usually repaired by removing and replacing the throtte control unit. I would suggest having an expert from YourMechanic come to your location to diagnose and inspect your vehicle at your earliest convenience.

Why does my air conditioner stop cooling when the car is on idle or at a stop in a traffic light?
ANSWER : Hello. Was the A/C working properly before you had the condenser replaced? Your previous mechanic was correct that the condenser was likely the source of the issues. Now that the condenser has been replaced, we know its working and can tell its the cooling fan that is failing to provide adequate air flow. You should turn your attention to the fans. They can fail in several ways including the fan clutch, fuse, and its main control module. You may also want to verify that the connections are clean, dry, and tight. The first step is to check and see if the fans are working at all, or if they have not been working this whole time. If the fan is not working at all, it or its motor should be replaced. If the fan is working intermittently then there will need to be more testing to determine what is causing it to only respond to certain signals.