Why does my car slow down then speed up?

There are a few reasons why your car might be doing that.

First, the most common reason is that you’re driving in the rain. When you’re driving in the rain, your windshield wipers can’t clear all of the water from your windshield.

This leaves some of it to build up on top of your windshield and fog up with your defroster. The windshield wiper fluid will then run down into your vent/defogger grid and drip onto the back of your front bumper, which causes a short circuit in one of its electrical components.

Another possible reason is if you have recently had an oil change or maintenance performed on your vehicle by an unqualified technician, they may have caused an issue with either one or both of your oxygen sensors.

These are used to measure how much oxygen is present in exhaust gases coming out of the engine. If there’s not enough oxygen being consumed by the engine, it will cause it to run lean and eventually stall out completely.

What causes and solution of this problem?


  1. Oil pressure is low, causing your car to lose power.
  2. Your engine is overheating and boiling the oil, causing it to lose power.
  3. our fuel pump is faulty and not pumping fuel into the engine.


  1. Check your oil level and make sure you have enough in there to keep the engine lubricated. Consider adding a little bit more if you think it may be low.
  2. Check your coolant levels and make sure they’re all full. If they’re not, add more until they are full again!
  3. Try to get your vehicle towed to a mechanic as soon as possible; they’ll be able to diagnose why your engine is giving out on you like this and hopefully fix it before it causes more damage than just slowing down when you accelerate then speeding up again later on down the road.

How do you fix it?

If your engine is running lean, the first thing you should do is check the fuel injectors. If they are clogged or not functioning properly, they will need to be cleaned or replaced. Another common cause of a lean engine is a vacuum leak. These can be located under the hood or under the car.

Vacuum lines allow air to flow into certain components inside the engine, such as the intake manifold and throttle body. If these lines are leaking air, it will affect the amount of oxygen going through your engine and cause it to run lean.

The best way to fix this problem is to find and repair any leaks in the vacuum system.

Your tires might be low on air or balding.

Low tire pressure will cause your car to use more fuel. Check the air pressure in your tires and fill them up if they are low.

You should also check for any cuts or damage on the tires that might be causing them to leak air. If your tires are worn down to the threads, it is time to replace them.

Replacing your spark plugs or coils.

Spark plugs and coils can cause your car to run lean because they are what fire the fuel in your car. If these parts aren’t working properly, it will cause your engine not to burn all of the fuel that it is supposed to be using.

If you have recently had spark plugs or ignition coils replaced, have them checked by a mechanic.

This matters because if your car is not running at peak performance, it can negatively impact gas mileage. It is important to keep up with maintenance on your vehicle in order to get the most out of it.

What can I do if it happens while I’m driving in traffic?

If you’re driving and your engine starts to run lean, there are a few things you can do:

1. Take your foot off the accelerator – this will help reduce the amount of fuel that’s going into the engine.

2. If possible, pull over to the side of the road and stop – this will give your car a chance to recover.

3. Put your hazard lights on so other drivers know you may be having trouble.


If your car’s engine starts to run lean, it is important to take action immediately. Taking your foot off the accelerator, pulling over if possible, and turning on your hazard lights will help you avoid further damage and keep yourself safe.

If you need your vehicle repaired or inspected as soon as possible, call your local auto mechanic for fast service.

Steven Hatman
Steven Hatman

We break down every information into easy-to-understand articles that cover all the categories anyone who owns a car needs to know about, such as oil , brakes , tires and etc. Our car guide is free and updated regularly for you to use as a resource, not only when you have an issue with your car but even before buying a new or used car! We also give tips on what to look for in each category or part of your vehicle.