Better Fuel Economy
Everyone knows that the miles per gallon, or MPG, of a vehicle, relate directly to its routine maintenance and condition. Meaning, the fuel economy will be much better if the vehicle is in much better shape. Everything involved with the car, from changing the oil to the tread on the tires, has a direct impact on the gas mileage and performance, and that is why routine maintenance is so important.
One commonly overlooked place that gets very dirty and gets little attention is the throttle body. The throttle body is the part that receives filtered air and supplies it to the intake manifold of a fuel-injected vehicle. Much like a carburetor, this part can get very gummed up with carbon residue fired off the combustion chamber. Therefore, at about 50-60,000 miles, it is necessary to clean it to remove the carbon buildup and restore the fuel efficiency and performance that the engine has lost over time.
Two Example Vehicles
The pictures here are from a 2007 Chevy Trailblazer with the 4.2 V6 (wife’s vehicle) and a 2001 Dodge Ram 1500 with a 5.2 V8 (mine).
What You Will Need
General tools are needed to remove the parts of the intake system and can vary from car to car. A screwdriver set, a socket set, some rags or shop towels, an old toothbrush, and some throttle body cleaner are the items that will get the job done. I would recommend using an overspray shield while cleaning like a flattened box or old newspaper, so there is less clean up.
Getting to the Throttle Body
The specific steps to this process will be different for every vehicle, but this is a good time to check the condition of the air filter because the air filter housing is the first piece to come off. Sometimes the air filter housing sits right on the throttle body, and sometimes the housing is connected by a tube. Either way the best quality cleaning will be achieved with the throttle body removed from the car, and some wire plugs and harnesses will need to come off as well as a vacuum tube attached to the body. If there is any trouble remembering where they go use masking tape to mark them with a number.
Before unbolting the throttle body, remove any wire harnesses, plugs, and vacuum hoses. Most will have a throttle linkage that will need to be disconnected; remember to label any connections that you might forget.
1. Chevy Trailblazer
How Do You Clean a Throttle Body?
The actual cleaning is done with throttle body cleaner, an old toothbrush, and some shop towels. The cleaning is much easier to perform with the body removed from the manifold; the gasket will need to be replaced but are only a few dollars. If the body is easy to clean while on the manifold, then hold the throttle plate open and spray into the body. Scrub the all residue with the toothbrush until the metal is clean. Use the rags to wipe away any residue left behind, as it is very important to clean it thoroughly. Most aerosol cleaners can cause the plastic to corrode so be very careful about what you spray and your overspray. Take notice of the intake manifold as they can be made of plastic, and removal and cleaning of the throttle body would be recommended.
Investigating the Check Engine Light
The Chevy had about 80,000 miles on it, and had the check engine light on. After a trip to the friendly Autozone where they read the code that the electronic control module, or ECM, displayed, the determination was there were actually four codes, and explanations for two of them weren’t available to me. Those codes were B0455 and U1000, but the other codes, P0506 and P1400, were in relation to a dirty throttle body or a bad idle air control valve, IAC, which, like its name, controls the idle.
The IAC is a solenoid mounted on the throttle body along with a throttle control sensor and mass air flow sensor. These sensors send information to the ECM, and the ECM adjusts the settings for the best performance and efficiency.
My determination was that the codes all came from the same place: the throttle body. Fix that, and all the other codes go away, and if that doesn’t work the whole throttle body will need to be replaced because the sensors and solenoids are encased in plastic. This particular throttle body cost about $300.00. After the cleaning is complete, reassembly is the opposite of disassembly, being sure to connect the plugs and hoses in the correct places. After starting this vehicle, the engine ran a lot better, but the code won’t reset itself. This vehicle went back to the parts store to have the ECM reset with a scan tool. Since then the car has recovered its power and efficiency and has run a lot easier.
Cleaning the Chevy Throttle Body
2. Cleaning the Throttle Body of the Dodge Ram 1500
The other pictures are of a throttle body of my truck, a 2001 Dodge Ram 1500 with the 5.2-liter engine. This engine has about 130,000 miles on it, and it shows in the excessive carbon build up on the underside of the body and throttle plate. The IAC and other sensors are more apparent on this one and easily accessible to cleaning. Removal of the IAC valve is necessary because this piece is exposed to excessive carbon build up that restricts the movement of the plunger. This causes the ECM to compensate for the loss by using more gas, hence the poor gas mileage. After removing the throttle body on this truck, I noticed that the carbon build was bad right on the top of the intake manifold and by removing the body I was able to clean into the manifold a bit more.
After reassembly of the intake on the truck I started it up; the truck barely ran, and the check engine light was on. Fortunately, most Dodge and Chrysler vehicles have a way to display the trouble codes if the vehicle has a digital odometer. Simply turn the key to the ignition without starting the engine and off for a cycle of three times. The digital odometer will show a set of four lines while it scans for codes then display any codes that it finds. The display will show ‘done’ when all codes have been displayed. The code displayed was P0505 which is similar to the other codes that the Chevy had displayed. This is because the ECM was still using the old settings of a dirty throttle body. To clear the ECM, disconnect the battery for about one minute then reconnect. This clears and resets the memory of the ECM, but also clears the memory of the radio.
*Note: Most major auto parts store like Autozone or Advanced Auto Parts will scan your car’s ECM for free.
This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.
© 2011 Jacob Harding