My 2003 Saturn L300 makes a knocking noise only in revers...

Q: My 2003 Saturn L300 makes a knocking noise only in reverse. Any idea's?

asked by on July 09, 2017

Knocks with a "sputter" while in reverse only. It doesn't do it in any other gear.

My car has 166683 miles.
My car has an automatic transmission.

This may be a sign of a faulty MAP sensor as the vehicle responds adversely to a load put on the motor (i.e. putting it in gear, making turns (which makes use of the power steering pressure switch) turning on AC or engaging the brakes). The Manifold Absolute Pressure (MAP) sensor senses engine load and generates a signal that is proportional to the amount of vacuum in the intake manifold. The engine computer then uses this information to adjust ignition timing and fuel enrichment. When the engine is working hard, intake vacuum drops as the throttle opens wide. The engine takes in more air, which requires more fuel to keep the air/fuel ratio in balance. When the computer reads a heavy load signal from the MAP sensor, it adjusts the fuel mixture to slightly more rich than normal so the engine can produce more power. The computer will then retard (back off) ignition timing slightly to prevent detonation that can damage the engine and decrease performance. This may also be caused by other closely related components such as a dirty or failing mass air-flow sensor, a faulty throttle position sensor or potentially a vacuum leak. I would recommend having an expert from YourMechanic come to your location to diagnose and inspect your vehicle.

Was this answer helpful?
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

Get a quote

What others are asking

Tugging while shifting from first to third gear, the engine lacks power

Hi there. The most common cause of this is a bad catalytic converter. When it fails, it will clog internally and will restrict the exhaust. This will cause a serious lack of power like what you are experiencing. It can...

There is a rattling noise coming from the exhaust. Car begins to jerk with this and sometimes it turns off.

You may have a catalytic converter that has broken up inside. The business part of the catalyst is made of ceramic material, (yes just like the clay pots) which is coated with the various precious metals that facilitate the reaction...

Whining sound when accelerating half the time.

Hi there: Although it's possible that the whining noise might be caused by the overdrive, it's also possible that this noise is caused by bad or failing wheel bearings. As the wheel bearings begin to age, they will lose lubricity...

Related articles

2007 Nissan Versa vs. 2007 Saturn Ion: Which One Should I Buy?
Compact cars as a class are generally meant to be commuter vehicles: with excellent gas mileage, an entry-level price point, and decent safety ratings for those who are on the road the majority of their time. These cars also make...
Saturn Certified Pre-Owned (CPO) Car Program
Drivers Drivers who are shopping around for a used Saturn vehicle may want to check out cars under their certified pre-owned program. Many manufacturers have a certified pre-owned (CPO) program, and each one is set up differently. Read on to...
Understanding the Saturn Oil Life Monitor and Service Indicator Lights
Car symbols, or dashboard lights, are a car service reminder. The Saturn Oil Life Monitor indicates when and what service your car needs.