5 Symptoms of a Bad Secondary Air Injection Pump

(Updated on September 28, 2020)

If you’re wondering what a secondary air injection pump is, you’re not alone. In this article, we’ll go over the purpose of the secondary are pump as well as the symptoms you should watch for that indicate the pump is failing.

What Does a Secondary Air Pump Do?

The secondary air injection pump (also referred to as a smog pump or SAI pump) is responsible for lowering the number of carbon emissions that come out of the tailpipe of a vehicle. This is necessary since a vehicle engine is never 100% efficient in the combustion process.

The pump lies after the exhaust manifold and before the catalytic converter of the vehicle and it can reduce carbon emissions by pumping fresh air from outside into the exhaust stream. By the time fumes leave the tailpipe, there are fewer hydrocarbon pollutants in them. This promotes a safer environment by cutting down on air pollution outside.

If there is ever a problem with your secondary air injection pump, then more hydrocarbon pollutants will be in the fumes which come out of your tailpipe. You won’t realize this until you receive an emissions test.

Either that or you’ll experience a lot of unfortunate symptoms that will affect your engine. Both scenarios are not something you’ll want to happen. They can make your life rather difficult if you do.

Top 5 Bad Secondary Air Injection Pump Symptoms

Secondary air injection pump failure is easy to recognize if you know which symptoms to watch out for. Below you’ll find the five most common symptoms of secondary air injection pump failure.

If you notice at least two of the symptoms occurring, there’s a good chance you’re dealing with a faulty secondary air injection pump and you need to get it serviced right away.

1) Check Engine Light

check engine light

One of the early symptoms of a bad secondary air injection pump is the Check Engine warning light turning on. The engine control unit can automatically detect when the secondary air injection pump has a problem.

Since the functionality of the air pump impacts the engine, any problem with it will activate the Check Engine warning light on the dashboard. To confirm the actual cause of the check engine light, you will need to use a car code reader to retrieve any error codes that were stored.

2) Failed Emissions Test

emission test failure

The purpose of the secondary air injection pump is to reduce hydrocarbons in your emissions system. So, if you have a bad secondary air injection pump, then it means your emissions system will be allowing too many hydrocarbons to be released into the atmosphere.

Not only does this spell trouble for the environment, but it also spells trouble for whenever you get an emissions test. If you happen to live in a state which requires emissions testing, you will fail the test if your secondary air injection pump is bad.

3) Weak Acceleration

car hesitates when accelerating - gas pedal

A faulty secondary air injection pump will cause problems for the air-to-fuel ratio in your internal combustion engine. If this ratio is too lean (not enough fuel), then your engine will have trouble generating speed whenever you step on the gas pedal.

Poor acceleration could be caused by several mechanical issues, but a bad secondary air injection pump is certainly one possibility. A failed emissions test in conjunction with weak acceleration is a decent indicator that it is the pump’s fault.

4) Engine Stalling

You may be driving normally and then suddenly experience engine stalling or hesitation in your vehicle. A secondary air injection pump that is wearing down can cause inconsistent power gaps from the engine.

One minute the power may be fine, and the next the RPM drop too much and the engine shuts off. If the pump is not replaced, the engine may continue to stall at the worst possible times.

5) Low Idle

rough idle

When your engine is idling, check the tachometer and see what the current RPM is. The normal RPM of an idle engine is somewhere between 600 to 1,000 RPM. But in situations when the secondary air injection pump is not working, you can expect the RPM to drop. This may cause the car to vibrate or even stall as noted above.

If you’ve already experienced engine stalling, poor acceleration, and a check engine warning light, then you need to have the secondary air injection pump checked out immediately. If it is proven to be the problem, have it replaced by a certified mechanic.

11 thoughts on “5 Symptoms of a Bad Secondary Air Injection Pump”

  1. Hi
    Can this pump cause the anti pollution fault in peugeot 307 and the engine stalling. Idle like it gonngonna cut off..?

  2. I find this a complete cheat. So you add air to the exhaust, diluting the exhaust but not REDUCING the amount of absolute HC’s coming out. So in effect you are not reducing emissions but just lowering the ratio out the tailpipe. Seems like a useless effort instead of trying to get the engine to run more efficiently. Lots of old smog/ AIR systems, when removed result in markedly higher MPG/KPL which by itself would lower the overall emissions without all the added complexity resulting in a net reduction of CO and HC’s. That’s government for you. Forget logic and science.

    • You’re right, it does dilute the exhaust. But it’s main purpose is to help heat up the primary catalytic converter quicker so it can effectively filter out emissions sooner than without the secondary air system.

  3. Exactly. In my state they try and force you to buy new cars. Even paying you more than it’s worth to get it off the road. Thanks California.

  4. Mine is making a vacuum sound, no check engine light. It takes a while to start. It’ll start right up after driving, I guess because the fuel circulated. It’s a vw beetle but cant find anything on it. How much longer can go until I can get it fixed?

    • Hard to say how long you can go, I’m not sure what the problem is. You could try checking for vacuum leaks. The sooner you can get it addressed, the better.


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