Skip the auto shop - Our mechanics make house calls

Q: Won't drive over 20mph. Reduced engine speed

asked by on

My check engine light came on today. It was driving fine earlier. I went to drive it again and it started to act funny. Almost like it wasn't getting enough gas. Then it said reduced engine speed. Now it doesn't drive over 20mph.

My car has 158000 miles.
My car has an automatic transmission.

Hi There, This may be a sign of a clogged catalytic converter. The catalytic converter converts toxic exhaust gases into less harmful pollutants that are suitable to be expelled into the atmosphere. When this is clogged, this causes these gases to be backed up into the exhaust system not allowing the engine to breathe properly. When this happens, the engine is forced to work much harder to expel these gases. This often results in the engine bogging down, hesitating, shaking and causing very poor fuel economy. This should also cause a check engine light to come on as the O2 sensors should be reading the incorrect amounts of oxygen in the exhaust gases if this is your problem. I would recommend having an expert from YourMechanic come to your location to diagnose and replace your catalytic converter.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

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

Get a quote

What others are asking

Q: double-lock keychain horn very weak 2007 ford f150

Hi there. Usually when the vehicle horn is weaker than normal, it's an indication of a problem with the horn relay. It might be a good idea to replace the FOB remote battery first as this is a fairly inexpensive...

Q: My 2013 chey impala ltz reads engine idle and trans hot what do I need to do to stop this from happening and my trans is not shift

The overheating of the transmission might be due to it being stuck in too low a gear for the vehicle speed. The transmission in your car is electronically controlled and uses a transmission pressure control solenoid which occasionally fails. The...

Q: Brake light on with cruise control kicking off

Hi there. Most of the time this is caused by a bad brake switch. When the switch does not work the computer cannot tell when you apply the brakes, which will affect the braking and cruise control systems. It may...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...