Tech Corner: Symptoms of A Bad Throttle Body

July 26, 2023July 18, 2023 Mark Williams 0 Comments BBK Performance, Engine Maintenance, Engine Performance, Tech Corner, Throttle Bodies

Learn to recognize the symptoms of a failing throttle body and understand when it’s time to consider an upgrade.

Throttle bodies don’t get nearly as much love as they should. While brakes, spark plugs, oil, and even the shocks are regularly inspected as part of your preventative maintenance routine, the throttle body often goes untouched. As simple as it is, it’s easy to take for granted that it’s always going to work. That’s simply not the case, though.

As the mouth of your engine, the throttle body is tasked with the immense responsibility of letting that thing breathe. Over time, the moving parts wear down, get all kinds of grimy, and can even fail to keep up with high-performance modifications. Considering just how important it is to your engine’s function, it’s something you really do need to pay attention to.

The good news for you is that the throttle body is a simple piece of equipment. It doesn’t take a whole lot of time and effort to show it the love it deserves. Even better, swapping one out for a performance model that can take your ride up a link or two on the food chain is equally as easy. And to make sure you enjoy the process of repairing or upgrading your throttle body, we’re here to layout the basics that’ll help you sidestep any frustrations.

What does the throttle body do anyway?

Before we get into the weeds, let’s talk about what the throttle body does in the first place.

An engine is a pump that converts air and fuel into energy. The throttle body is a valve that’s responsible for modulating airflow into the intake manifold that then diverts it to each cylinder. The more the valve opens, the more air can flow into the engine, allowing it to burn more fuel and produce more of that sweet, sweet power.

Most cars today are working with a direct injection system that separates the injectors from the throttle body by placing them directly in the cylinders. This is known as a direct injection system, and the throttle body is little more than a butterfly valve connected to the accelerator pedal.

However, throttle body injection systems are popularly featured on older vehicles where an engine that was originally designed to work with a carburetor has been upgraded to fuel injection. Even so, the function is largely the same — only the throttle body looks a lot like a carburetor, with fuel injectors built right into it.

What are the signs of a bad throttle body?

Throttle bodies do get dirty over time, and you should clean them up regularly as part of your routine maintenance schedule. How often you do so will depend on a few factors.

The owner’s manual usually suggests cleaning the throttle body every 100,000 miles, but that’s not something you always want to stick to. Especially since you don’t live in a perfect world where the air is clean and everything works right. In fact, you probably willingly subject your ride to the kind of abuse that really shortens up that maintenance interval by a considerable amount. (Don’t feel bad, all gearheads do.)

Lucky for you, you don’t have to guess when your throttle body is dirty. Chances are that your car’s going to tell you the throttle body needs a cleaning well before some magic number rolls over on the odometer.

As that thing gets caked in dirt and other grime, your engine will struggle to breathe. The performance will start to fall off, fuel economy will suffer, idle speeds will be all over the board, and you may even experience stalling from time to time. That’s especially true considering that your mass airflow sensor will be equally grimy, adding even more heartache to the situation.

Can I fix my throttle body?

Nobody reading this is happy with performance falling off. And considering the way you drive, you definitely don’t want fuel economy to take yet another hit, either.

Letting dirt, carbon, and other gunk sit on moving parts is also a recipe for excessive wear, so you shouldn’t let the thought of having to invest in a new throttle body leave you dragging your feet to the repair, especially when that’s not always the solution.

More often than not, throttle body woes are remedied with a simple cleaning.

You will need to remove the throttle body to clean it. (Relax, even on the most advanced cars, doing so usually only requires removing a few bolts and sensors.) Once it’s off, throttle body cleaner and a brush are generally all you’ll need to rid the mouth of your engine of any unwanted deposits.

Keep these tips in mind when cleaning the throttle body to help you pinpoint any underlying issues:

Look for heavy deposits. It’s always wise to take note of exactly what’s on the throttle body before you start cleaning it off. A little bit of carbon and dirt are to be expected, but heavy deposits of either are definitely cause for concern as they indicate that issues exist elsewhere.

Look for oil. Another problem to take note of is oil on the throttle body. This generally means there is excessive crankcase pressure, telling you that your rings are likely due for replacement.

Look for damage. While the throttle body is off, you also want to visually inspect all the parts for any signs of damage to ensure it’s still serviceable. Take the time cycle the valve as well. You want to make sure it moves freely, seals tight, and doesn’t get hung up anywhere.

If there are signs of damage or excessive wear to any of the components, replacing the throttle body altogether is likely your best bet.

What if dirt isn’t the problem?

An important factor that you need to keep in mind is that your car is equipped with a throttle body that would help it breathe under normal driving conditions with stock parts. It might be capable of supplying adequate air to the engine when you jump on the throttle out on the streets. It might even set you back in your seat and put a smile on your face. But it’s not really designed to provide maximum performance on the track, and it’s definitely not the right choice for modifications that make that engine even hungrier for air and fuel. By the time you finish installing cams, forced induction, nitrous, new heads, or a combination of any of the above, you’ll find your engine outrunning that stock piece.

Determining if a throttle body is too small is easy. It’ll run fine at low to part throttle, but struggle to produce power at high RPMs. This happens because your engine starts to demand more air than the throttle body can flow at those higher speeds.

That sounds like a bigger problem than it really is, though. Aftermarket throttle bodies are widely available for popular performance cars and trucks. Better yet, they’re designed to bolt right in place of the factory unit, making installation as easy as routine cleanings.

An upgraded throttle body is a bolt-on replacement outfitted with bigger or more valves to instantly improve airflow to the engine. How much bigger you should go really depends on the mods you have made to the engine and what you intend to use the vehicle for. If you’re unsure of where you need to be, it’s always good to talk to a specialist who can point you in the right direction.