Drone in 2007 Grand Marquis may be exhaust

Q: I would appreciate some help with my 2007 Mercury Grand Marquis (27,000 km). When I accelerate or decelerate I get a drone sound – it's a bit like a subdued hotrod. The dealer can't seem to find the problem, or perhaps he doesn't want to know.

Technician Tom Zekveld replies:

Noise issues can be deceiving and frustrating. First, you should confirm that your vehicle really has a problem noise. The best way to rule out a normal noise is to drive a similar vehicle and compare.

You indicate that it sounds like a subdued hotrod. From that I interpret you are concerned with the exhaust note. Some exhaust tone is engineered into vehicles depending on the desired affect. To be sure, the Grand Marquis is all about a smooth "quiet" ride.

Has the car been hit? If so the exhaust may be slightly misaligned, causing it to contact a heat shield or floor pan panel. The exhaust system needs room to shift when accelerating or decelerating. Insufficient clearance will bring on a droning noise if the exhaust makes contact with shielding or panels.

Q: My Mazda Millenia 2002 is really emitting excessive exhaust on cold starts. It seems okay when the engine is warm. It does not burn excessive oil. My engine light has been on for some time. Are they related?

Technician Tony Prochilo replies:

When your Mazda Millenia's check engine light lit up, the on-board electronic control unit (ECU) detected a failure and stored a diagnostic trouble code in its memory to aid in vehicle diagnosis. This stored code may or may not have something to do with the excessive exhaust emissions on start up that you are experiencing.

Excessive exhaust emissions may be caused by an inaccurate air/fuel mixture, or perhaps a worn or damaged engine that is using antifreeze or engine oil during the normal combustion process.

First, a quick visual inspection of the exhaust tail pipe upon start up will be able to confirm if any of the above mentioned are the reason for the excessive emissions.

Next, a scan of your Mazda's ECU will confirm what the stored diagnostic trouble code is. You may find the code has something to do with your exhaust concern or it may be an unrelated condition that also requires further diagnosis and repair.

Service Centre technician Tom Zekveld is an independent garage operator.

Tony Prochilo is an automotive instructor at Centennial College, Scarborough.

Email your mechanical questions to wheels@thestar.ca.

Letters may be edited. Letter volume prevents personal replies.

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