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Mercury Grand Marquis Stalls

Q. Hi Vince, I have a 1999 Mercury Grand Marquis with 111,000 miles on it. I am the original owner. It has Ford's 4.6 liter V-8 engine, air conditioning, and automatic transmission. All service recommendations are current, and have been maintained for the life of the vehicle. At about 85,000 miles I began experiencing starting and idling problems.

Mercury Grand Marquis Stalls

The car is frequently, but not always hard to start, requiring a slight pressure on the accelerator pedal to get it started and keep it running. It also stalls frequently when idling, whether in drive or neutral. Once started, the car may run alright, or act up all day long, requiring a constant pressure on the accelerator even at idle to keep it running.

One odd thing. When these problems are present, I hear a muffled pop (more like a puff) under the hood and feel a slight surge in engine speed immediately before the problems disappear. It sounds like a vacuum problem, but I have been unable to find any leaks.

I have serviced the fuel system once myself, and also had it professionally serviced. (Still has original injectors.) I have had the OBD2 checked, and there were no trouble indications. Other than this, the car runs great and gets good fuel mileage, 23-24 city, 26-27 highway. You're my last hope before taking it to the shop and spending big bucks on it.

Thanks in advance for your help.
Lee

A. I guess the first thing I would do is to give the throttle chamber a good cleaning and see if that helps. A lot of idle problems are cured in this manner. Also check for disconnected vacuum lines since this could cause the problem.

I wonder if that "pop" you hear is the EGR snapping closed? The next time it happens, have someone tap on the EGR valve. If it's stuck that will free it up and allow it to close. Then you'll know where the problem is.

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