A dirty or gummed up throttle body is one of the most common problems that can occur on every type of vehicle today.

This problem can cause check engine lights to come on.

Check engine light

Engine surging when coming to a stop and even the possibility of stalling the engine are other symptoms as well.

Diagnostic connector
Scan tool

Scan the check engine light to read fault codes for repair.

The throttle body on an engine needs to be clean in order to perform correctly.

How does a throttle body get dirty? Let’s start with emissions. Part of being environmentally friendly is to filter everything, especially the air that the engine breathes.

In order to positively vent the engine crankcase vapors from the engine oil, it has to be routed back into the engine through the throttle body. Traditional oils are carbon base oils. When the carbon base oil vapors vent through the throttle body, small amounts or particles of the oil attach to the inside of the housing. Oil in a varnish or solidified carbon form builds up where the throttle closes, causing a restriction in the amount of air that the engine needs when idling. Now you can see why an engine might surge or die. Here is a procedure for cleaning out the build up as a maintenance item.

Here is a 2004 Chevrolet Malibu with a 2.2 liter 4 cylinder. This vehicle has all 3 of the symptoms, engine warning light and poor idle quality with occasional stalling.

Locate the air intake system.

Air intake system

This is where the air comes into the engine from the air filter to the throttle body.

Unscrew the breather tube clamps.

Remove clamp
Remove breather tube

Remove the breather tube from the throttle body.

Check the butterfly for build up.

Inspect butterfly
Inspect throttle body

Open and inspect the throttle body internally.

Note:

When using carburetor cleaner, make sure to wear safety glasses and work in a well ventilated area.

Caution!!

When working with carburetor cleaner, use caution around painted surfaces, plastics, and anything hot, this product is extremely flammable and can damage paint and plastics!!

Purchase a can of carburetor cleaner.

Purchase carburetor cleaner
Spray throttle housing

Spray the housing and use a shop rag to wipe out the buildup.

Clean out throttle
Dirty shop rag

Carburetor cleaner is the only spray that will dissolve and remove the varnish. This was a very dirty housing.

Install the breather tube.

Install breather hose

Secure the clamps.

Locate the diagnostic connector near the driver’s side foot well

OBD II connector
Plug in scan tool

Plug in an OBD II scan tool to clear the fault memory and shut off the engine light.

Clear codes and monitor

There could be a number of faults stored that are bogus faults, due to the uncontrollable idle on the engine. Sensors and control units are trying to compensate for a lack of air at idle by leaning out the fuel to control the engine speed.

The main reason in checking this throttle body was for surging and low idle. After cleaning the throttle body, the engine idle and driving conditions were restored.

If you paid a repair shop to perform this service you would be charged at least 1 hour labor for the check engine light, and 1 hour for the cleaning. Base an estimate on a shop labor rate at $80.00 per hour.

If you performed the repair yourself, the carburetor cleaner is around $3.00 and a roll of shop towels $2.00.

Comparison pricing

Cost at a repair shop $160.00

Cost to do it yourself $5.00

A good preventative maintenance would be to clean your throttle body every year and eliminate the possibility of seeing the check engine light for this reason.