Skip the auto shop - Our mechanics make house calls

Q: Rough Start

asked by on

Hello! I have a 2003 Lincoln Ls V8. Only sometimes when I start the car up, it idles a little rough until I get moving. Then it runs fine. Other times when I start it, the car feels like it wants to stall out. But again, once I give it gas, it's perfectly fine. I also noticed a werid smell coming from the exhaust and I've lost a little bit of gas mileage and acceleration no check engine light. Can you help?

My car has 74000 miles.
My car has an automatic transmission.

There are a number of things that can cause poor fuel mileage. A faulty camshaft position sensor is one of them. The camshaft position sensor is a magnetic sensor that monitors camshaft speed to regulate ignition timing and fuel injection timing. It gathers and sends information about the car’s camshaft speed (and as a result the position of each piston) to the car’s electronic control module. This information is received by the computer, which then uses this data to further calculate the time of ignition and the timing of fuel injection required by the engine. When this is not working properly, you may experience a drop in power, poor idling, poor fuel mileage and problems starting the vehicle.

A clogged or dirty EGR valve may also cause poor fuel mileage. The EGR valve is a small component designed to allow the flow of exhaust gases into the intake manifold in controlled amounts. Whenever you start the engine, the valve comes alive and waits in a closed position, blocking the flow of exhaust gases. Once the engine reaches operating temperature and speed increases, the valve, either through vacuum or electronic control will gradually open, allowing burned exhaust gases to enter and combine with the air-fuel mixture inside the combustion chamber. When the EGR valve is clogged or dirty, as they are prone to, it may not function properly causing the engine to idle rough, stall at idle speeds, cause the car to get poor fuel mileage, or emit a strong smell of fuel due to excess hydrocarbons which also results in failing emissions tests.

A clogged or failing catalytic converter can cause the vehicle to have poor fuel economy. As you may already know, 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. I would recommend having a professional from YourMechanic come to your location to diagnose and inspect your vehicle.

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: FRONT ROTORS REPLACEMENT & KNOCKING SOUND GOING OVER BUMPS AND NORMAL DRIVING

In order to remove the rotors on the front, the calipers and caliper brackets will need to be removed first. Once the caliper and bracket have been removed, the rotor will come right off. As for the suspension issue, Lincoln...

Q: My car starts to overheat in stop and go traffic until I turn on the heater. It then goes back to normal.

You may have a leak you have not seen if you had to add coolant. You should also not have to turn on the heater to full blast to cool the engine. This tells me you either have a cooling...

Q: Will 2006 Explorer rear struts fit in a 2003 Explorer?

Hi there - no, not according to parts interchange charts. There was a model revision between 2005 and 2006, and the rear shocks changed over that revision. Shocks from a 2002-2005 Explorer should interchange properly.

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...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.