What Are the Symptoms of a Bad EGR Valve?

What Are the Symptoms of a Bad EGR Valve?

Exhaust gas recirculation systems aren't exactly the most glamorous systems in the average car, but they do perform several very important jobs. An EGR might not help you get where you're going any faster or looking any better, but a working one will get you there a good deal cleaner and cheaper.

Symptoms
An EGR valve works by recirculating used exhaust gases into your engine. These gases contain unburned fuel but very little oxygen, and they're very hot. A hot intake charge carries less oxygen, so a working EGR system effectively makes your engine act smaller than it really is. In terms of driving, an EGR valve that's stuck open will cause a noticeable drop in horsepower at the very least. Along with that may come detonation -- "knock" or "ping" -- under hard acceleration, and the attendant cylinder misfires. The engine will also see an open EGR valve as a massive vacuum leak, so expect hard starting and a very rough idle. An EGR stuck closed or clogged with carbon won't exhibit many symptoms, since engines don't technically need them to run. But expect a very noticeable drop in fuel economy, a noticeable gasoline smell from the exhaust pipe, a very hot catalytic converter, or all of the above.

All modern vehicles monitor the EGR system, so any fault with the system should trigger a check-engine light. You'll get one anyway if the engine ends up detonating, misfiring or running rich; all of these will trigger diagnostic codes. But you should find EGR diagnostic codes along with them if the EGR is the source of the problem.

How to Check an EGR

How to Check an EGR

EGR valves in a car regulate combustion temperatures within the engine of a car. The valve recycles exhaust back into your car, which makes the car more energy efficient and reduces the amount it pollutes. A faulty EGR valve will result in either a clicking sound in the engine or an engine stall while it is idling. Luckily for car owners, the EGR valve is very easy to check, and you do not need extensive auto-mechanic knowledge in order to perform a thorough inspection of your EGR valve.

Things You'll Need

Owner's manual

Instructions

Turn the ignition on in your car, and leave the car in park. The engine should be allowed to warm up for several minutes before you inspect the EGR valve.

Pop open the front hood of the car.

Locate the EGR valve by consulting your car's owner's manual. The location of the valve will differ according to vehicle make and model.

Observe the EGR valve while someone revs the engine. If the EGR is functioning properly, a plunger like part will bounce up and down consistently. If the part is not moving fluidly, or will not move at all, your EGR needs maintenance and you should consult a mechanic.

What Are the Symptoms of a Bad EGR Valve?

What Are the Symptoms of a Bad EGR Valve?

Exhaust gas recirculation systems aren't exactly the most glamorous systems in the average car, but they do perform several very important jobs. An EGR might not help you get where you're going any faster or looking any better, but a working one will get you there a good deal cleaner and cheaper.

Symptoms
An EGR valve works by recirculating used exhaust gases into your engine. These gases contain unburned fuel but very little oxygen, and they're very hot. A hot intake charge carries less oxygen, so a working EGR system effectively makes your engine act smaller than it really is. In terms of driving, an EGR valve that's stuck open will cause a noticeable drop in horsepower at the very least. Along with that may come detonation -- "knock" or "ping" -- under hard acceleration, and the attendant cylinder misfires. The engine will also see an open EGR valve as a massive vacuum leak, so expect hard starting and a very rough idle. An EGR stuck closed or clogged with carbon won't exhibit many symptoms, since engines don't technically need them to run. But expect a very noticeable drop in fuel economy, a noticeable gasoline smell from the exhaust pipe, a very hot catalytic converter, or all of the above.

All modern vehicles monitor the EGR system, so any fault with the system should trigger a check-engine light. You'll get one anyway if the engine ends up detonating, misfiring or running rich; all of these will trigger diagnostic codes. But you should find EGR diagnostic codes along with them if the EGR is the source of the problem.

Signs of a Bad Idle Air Control Valve

Signs of a Bad Idle Air Control Valve

An idle air control valve is, in a very real way, the predecessor to the drive-by-wire throttle systems commonly employed today. It performs much the same function as any electronic throttle: to control the amount of air going into the engine so the computer can match it with the right amount of fuel. The only difference between these two systems is that an IAC is smaller and only works at idle.

Common Problem
Because an IAC valve controls air going into the engine only when the throttle is shut or almost shut, these are the only two times you're likely to notice it malfunctioning. The most common type of failure results from clogging of the IAC valve with carbon, dirt and debris, which restricts the amount of air going through and slows the valve's response time.

Classic Symptoms
Classic symptoms of a clogged IAC are a rough or unsteady idle, and stalling if the valve passage gets too clogged or the valve fails outright. Another sign is engine rpm that drops very low -- possibly to the point of stalling -- when you lift your foot off the gas pedal to slow down. This may be accompanied by an immediate, jerky deceleration as soon as you lift your foot off the pedal, and a backfire through the tailpipe as the engine loads up with excess fuel.

Less Common
Less common are valves that get stuck in the open position; in this case, you'll probably only see stalling at idle and hesitation during acceleration. Modern cars will almost always trigger a check-engine light following any kind of IAC failure, and may display codes specifically diagnosing that.

How to Adjust a Car Idle

How to Adjust a Car Idle

As cars get older and accrue more mileage, the idle speed of an automobile may be higher or lower than it needs to be, either wasting precious fuel or causing the car to stall out. Adjusting your idle is relatively easy, with the same basic procedure for any car. However, be sure to check the specifications for your car before doing any of your own maintenance.

Things You'll Need

Screwdriver

Instructions

Start your car and allow it to cycle through at least one period of going through a higher RPM rate. This will ensure that the engine is completely warmed up and you will be able to adjust the idle properly. It is important to allow the engine to warm up because you will be driving your car mostly at that condition. While the engine is warming, you can pop the hood of your car and prop it open.

Locate the throttle body. You can recognize it by tracing your air intake hose as it exits the air filter. The next part that the air hoses connect to is a metal part called the throttle body. Look on the sides of the throttle body until you locate a screw or a rubber casing that houses a screw. This screw is how you adjust your idle.

Remove the rubber casing for the idle switch by prying it off with a screwdriver. This casing is usually installed by manufacturers but is not needed for the performance of the idle switch. If your idle has been adjusted before, then there will be no covering over the screw.

Disconnect the idle air adjustment valve, which regulates whether the idle opens or closes depending on the air intake. Disconnect the valve by locating the electrical connector behind the throttle body. Be careful not to touch any hot engine parts while working on the idle.

Turn the idle screw, now exposed from the protective rubber coating, in order to adjust the idle. Loosen the screw in a counter-clockwise fashion to increase idle speed or tighten it in a clockwise manner in order to decrease the idle speed. Ideally, you will want the idle to rest at 650 RPM.

Reconnect the idle air controller valve electrical connection. Lower the hood and turn your car off.

High Idle Causes

High Idle Causes

A high idle in your car can cause you to worry. When the engine seems to rev up on its own while you are at a standstill, you may wonder if it's a sign of trouble that needs the attention of a mechanic. The answer to that question depends on the cause of the high idle. Some causes are harmless, while others can indicate the need for a repair.

Faulty Fuses

Most modern car engines control the engine idle speed through a motor called an IAC (idle air control) motor. One of the leading causes of IAC motor malfunction is a blown or faulty fuse. A malfunctioning fuse in any of the electronically controlled components including the air bag system can disrupt the function of the IAC motor and lead to a higher idle speed than usual.

Computer Malfunctions

Computers control a modern car's engine and transmission, its brake system and its airbag system. If the fuses are fine, the computer system itself in one of these components might be malfunctioning. If that's the case, that might be the source of the high idle speed in your engine.

In some cars, the powertrain control computer can misinterpret the information it receives about the idle speed, leading to higher idling speeds. Cold weather can trigger this problem, and it usually corrects itself once the engine is warmed up.

Leaking Vacuum

The IAC motor works with a vacuum port to control the engine's idle speed. By opening and closing a valve to the vacuum port at set intervals, the IAC motor sets the idle speed. If the seal on the vacuum port is leaking, that will interfere with the overall function of the IAC and may lead to high idle speeds. Often it is the hoses connected to the vacuum system that become damaged, leading to an imperfect vacuum.

Malfunctioning Throttle

The throttle system in the vehicle might not be working properly, which can cause engine stalling or high idling. Common causes of a throttle malfunction are a buildup of dirt and contaminants in the engine's secondary air intake or a cracked air intake tube.

IAC Motor Malfunction

The IAC motor itself may not be working properly. A short circuit in the motor can trigger high idle problems. Sometimes IAC motors develop high resistance in the circuitry, which slows the reactions of the IAC and can lead to idling problems.

The Causes of an Idle Surge

The Causes of an Idle Surge

Fluctuations in engine idle speed can be annoying and may even cause stalling at idle. Engine stalling can be dangerous, because power assistance is lost to the steering and brakes. Idle speeds below those specified by the manufacturer will affect the performance of the power steering pump, alternator and AC compressor. Emission control devices also require a minimum engine speed for effective operation. Surges that accelerate engine speed could cause unexpected vehicle movement.

Air Supply

A clogged or obstructed air filter can cause surging at idle, and foreign objects can enter the filter housing at any time. Any debris in the filter or housing might restrict air flow to the engine enough to affect idle speeds. Clean the throttle body or carburetor venturi(s) after replacing a severely dirty air filter. Aerosol products designed for this purpose are available at any auto parts store. Instructions for use are on printed on the can.

Fuel Supply

Fuel filters can become restricted and deny proper delivery at idle speeds. Mechanical fuel pumps may overcome restrictions and performance deficiencies at higher speeds. Incorrect idle speed settings or fuel mixture adjustments, and malfunctions in the fuel vapor recovery system can upset engine idle capabilities of carbureted engines. The appropriate fuel system cleaner added to the fuel tank can open clogged passages in injectors and carburetors that may be causing the surge.

Vacuum

Any extra air entering the intake manifold will lean the mixture at idle and surging will result. A visual inspection of vacuum hoses may reveal cracked or leaking hoses. A short length of tubing can serve as a make-shift stethoscope to pinpoint any hissing noises heard on a running engine. Cracked or clogged positive crankcase ventilation valves can adversely affect engine idle quality. Idle solenoids or controls should be adjusted to specifications after vacuum leaks are repaired.

Engine Issues

Ignition system problems can contribute to idle surge. Ignition timing and the condition of spark plugs and related components should be be checked before seeking professional assistance. Lack of compression, and valve timing and condition issues are complex to diagnose and usually affect overall performance, but can be more pronounced at idle speeds. Contributing emission system flaws may require advanced testing techniques or equipment. A visit to a qualified repair facility might be necessary.