Q: My car will not get over 20 mph. What is wrong?

asked by on November 14, 2016

Recently replaced the battery in my 2006 BMW 325i. My car had been parked for about a month when I finally got the battery replaced. After replacing it, it started right up but I received no warning lights or anything. But as I stated in the question, it will not go over 20 mph. What do I do?

My car has 136000 miles.
My car has an automatic transmission.

The battery replacement seems to be a coincidence and has no bearing on the symptom you are experiencing. The only exception to this would be if during the battery replacement, any essential wiring was disconnected or damaged, such as the wiring to any electronic throttle sensors or controls. Initially, I would recommend using a code scanner to see if any diagnostic trouble codes have been set. You can do this yourself or have a certified technician do this for you with an inspection. If no codes have set, the mechanic would check and see if the transmission is stuck in first or second gear, in which case the diagnostic would focus on the transmission controls including things like the shift solenoids, the valve body, and so forth. If there is nothing wrong with the transmission, the problem you are describing is likely due to a fault in the air induction system, the fuel supply, or the ignition system, although there is a possibility that a mechanical issue involving valve timing could cause this sort of symptom as well. A professional technician, such as one from YourMechanic, can diagnose your difficult acceleration problem to get to the root of the issue and then let you know of your repair options.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing


Experienced Mechanic?

Earn up to $70/hr

What others are asking

Brakes feel squishy
You are correct that excessive pedal travel can be caused by air entering the brake system. However, unless there is a leak or the system has recently been serviced, air should not have entered the system. There could be a...
Do i have to buy new engine if water rusty in plugs and car won't start..
It is very common for the cylinder head gasket on these engines to leak oil and coolant. You may have to replace the cylinder head if it is damaged. If you have water mixed in the engine oil, then you...
Wheezing when i press he gas more than 30 mph
Hello. The noises you are hearing are impossible to fully diagnose without the vehicle here. Lets begin with talking about that Check Engine Light. The light illuminates when certain codes (https://www.yourmechanic.com/article/how-to-read-and-understand-check-engine-light-codes-by-jason-unrau) are sent to the main computer. Not all codes...
Engine mangenent light all of a sudden. Limp mode
Hi there. Typically, when the engine management light comes on, there is a correlation issue between the APP (accelerator pedal position) sensor (https://www.yourmechanic.com/services/throttle-accelerator-pedal-position-sensor-replacement) and electronic throttle control TPS (https://www.yourmechanic.com/services/throttle-position-sensor-replacement) (throttle position sensor). When this occurs, the PCM (powertrain control module)...
How can I get my car to start? - 2007 Nissan Altima
Hello there, many common problems will prevent your 2007 Nissan Altima from starting properly. The steering wheel lock and brake switch are both common failure points but if these did not fix the issue the car will need further diagnosis....
Ford Explorer sport not shifting/running right.
Hi there. Thanks for writing into YourMechanic.com about your Ford Explorer. It's possible that you have a transmission speed sensor or other sensor that is sending inaccurate information to the ECU, or you have a mechanical issue inside the transmission....
Oil leaking from engine (not enough to leave driveway spots but still a leak) white/grayish smoke on startup only. No smoke while
External leaks could be from any of the oil seals on your engine and the cost to repair would depend on exactly where the leaks are located and how many seals need to be replaced. Certain seals are inaccessible unless...
changed electronic throttle body, wrench lights when stopping hard and taking off fast, lose power
Hi there. The wrench light is a service indicator light that is designed to alert the driver that routine service or maintenance is required. In some cases, this light is illuminated when excessive carbon is detected in the fuel system....
Having problem installing alternator in a 2005 nisson pathfinder. Bolts don't line up.
Hi there. Typically when bolts don't line up when everything else is properly aligned, it's due to the wrong replacement part being used. There are two things I would recommend. First, search online to find the recommended replacement alternator for...

Related articles

How Can I Prevent My Car Battery From Dying?
Your Your car battery is one of the most important parts of your car’s electrical system. Without the battery, your car simply isn’t going to work. Your battery works hard, and eventually, it’s going to wear out. So, how long...
How to Clean Battery Connections
Cleaning your battery connections, especially if the terminals are corroded, will help ensure the battery lasts longer and performs well.
How to Buy RV Batteries
RV RV (recreational vehicle) batteries come in many different types, and what type is best depends on the useage and conditions the RV (https://www.yourmechanic.com/article/5-essential-things-to-know-about-owning-an-rv) will be exposed to. Unlike cars, RV’s use multiple batteries. These batteries are used to power...