2001 Mercury Marquis Engine Stalling for no Apparent Reason

400 is too much to check coils unless you are replacing them all !! Most people guess with one or two new coils and start a system to swap them out. I would look into sensor problems before guessing ac problem. Definately get some other opinion before dropping piles of money on it, and keep us posted when you find the answer

Heck, the dealer would be cheaper than that! Go somewhere else. This guy wants you to pay for his education (he doesn't know how to fix it). Besides, testing individual coils is a waste of time. How does he explain the AC to Stalling relationship? I would more suspect a failing fuel pump but that's only a guess and I work on vehicles similar to yours every day! (Crown Victoria). 1 hour's worth of labor for diagnostics and an estimate - that's all.

Thanks for the advice; you got me thinking in the right direction. The shop is at the Dealer. Went down to listen to the AC and it seems fine. Decided to replace the coils. Went to NAPA for the parts; about $385 for 8 coils (Dealer wanted closer to $500 for coils). Gave the parts to the Dealer's service guy and asked him to do a tune up and replace the coils when they pulled and replaced the plugs. Service was $180 for the tune up, plus $100 for the original diagnostic. All in about $675. Towing was by AAA, so no additional expense on that. Car runs fine now. Car just needs to last another 18 months till the son driving it graduates. All-in-all a really good car. 300,000+ miles, and only a single major repair. Thank you Ford!

Every time I get one of our Crown Vic Patrol cars in with over 130,000 miles on it, I realize that those are a HARD 130,000. We're keeping them 'till 180,000 now. Surprisingly, in a fleet with over 800 of them, we see very few engine failures. I'm sure that your car will last just fine.

Thing is..... you can order all 8 coil packs new for far less then $ 60.00 each... I got all 8 coil packs new for less then $100.00 on line... Also, problem with the mercury's and crown vics is a common problem with engine stalling and sputtering.... The mass air flow sensor inside the air box..... It gets dirty quick, so just buy a can of MAF sensor cleaner from autozone or somewhere else.... usually about 7 or 8 bucks a can but will last a long time. All you gotta do is disconnect the hose from your air box, take out the air filter and spray the maf sensor, it will look like a wire, around where the hose connects to the airbox.... spray it reallygood for a few seconds.... reconnect and you should be good to go.... this is a common problem for this model vehicle..... I did the research online and tried it.... it has saved my but many times so I am incline to say its correct and proven!!!! Can,t hurt to try, and is very easy to do yourself, will save you hundreds of dollars!!!! No harm in tryng, just 10 bucks......lol...

Also, if the air filter inside the airbox is not fitted correctly, this can cause the same problem in this model car..... The air flow gets restricted, thus causing engine hesitation and stalling.... Happened to me on my 2001 mercury grand marquise. All I had to do was take it apart and clean it out, then reinsert it properly... Then all was good!!

If coils are bad then there would be a check engine light on. Have the codes read to know which coils are a problem. A lot of auto parts stores will read the codes for free.

A new set of coils is only $60 to $250 on Amazon. The labor to replace all of them would be about 4 hours.

4 hours ??? I bought the set of 8 new ones for $230.00 from Autozone & had them all switched out and backing it out of the driveway in 20 minutes.