Check Engine Light On

Amie Kreidler

Asked by Jun 20, 2016 at 09:47 PM about the 1999 Mercury Grand Marquis 4 Dr GS Sedan

Question type: Maintenance & Repair

I have a 1999 Grand Marquis. My check engine light is on and it says it is a
cylinder 6 misfire according to autozone machine. I have replaced the
spark plug, and properly gapped the spark plug cause the one I pulled out
wasn't. I have replaced them all and properly gapped them. I put a new coil
on cylinder 5 because it was broken and not on all the way either. I have
replaced fuel filter as well. I have put fuel injector cleaner in it as well. What
else can it be?

4 Answers


P0306 MERCURY - Cylinder 6 Misfire Detected - Possible causes - Faulty spark plug 6 - Clogged or faulty fuel injector 6 - Faulty ignition coil 6 - Fuel injector 6 harness is open or shorted - Fuel injector 6 circuit poor electrical connection - Ignition coil 6 harness is open or shorted - Ignition coil 6 circuit poor electrical connection - Insufficient cylinder 6 compression - Incorrect fuel pressure - Intake air leak

Amie Kreidler

well I think I found the problem when replacing the spark plugs there was oil in one cylinder and antifreeze came out of another. Is this a busted head?


Cracked head or head gasket. No easy solution. No matter what, it needs to be torn apart and checked, (magna fluxed) for a cracked head, and possible shaved for flatness. Sounds like this engine had gotten hot in order for this to do this, as it looks like the heads, and possibly the block are aluminum. Depending on what you want to do with the car your looking at around $3000 for a re-manufactured engine, plus labor. Depending on the condition of the cam shafts, and how many miles are on this thing, a re-manufactured head is around $500. These prices are from a warehouse I use in CA. so depending on where you live, this could be more.

Amie Kreidler

Thanks that's what I was thinking as well. I did see where the intake hoses can leak into the cylinder and I did a leak on a hose. i have clamped that and since then and replacing all spark plugs and properly gapping them the check engine light has gone off. There is no more skipping and jumping and losing power going up hills. I hope it's not the heads but will a professional mechanic look at it. Thanks for your help.

Your Answer

Add photo

Related Questions

Grand Marquis

Looking for a Used Grand Marquis in your area?

CarGurus has 2,571 nationwide Grand Marquis listings starting at $1,300.


Search Mercury Grand Marquis Questions

Mercury Grand Marquis Experts

#1 Tracy Hooks
Tracy Hooks
Reputation 4,820
#2 kbro
Reputation 1,910
#3 Js08016
Reputation 1,440
View All

Related Models For Sale

Used Ford Crown Victoria"
10 Great Deals out of 1,648 listings starting at $1,950
Used Lincoln Town Car"
49 Great Deals out of 2,401 listings starting at $1,542
Used Chevrolet Impala"
939 Great Deals out of 35,888 listings starting at $700
Used Ford F-150"
3,259 Great Deals out of 217,203 listings starting at $1,000
Used Honda Accord"
1,313 Great Deals out of 78,754 listings starting at $1,395
Used Chevrolet Tahoe"
1,146 Great Deals out of 36,615 listings starting at $1,995
Used Ford Taurus"
352 Great Deals out of 23,122 listings starting at $1,400
Used Cadillac DeVille"
2,400 listings starting at $1,600
Used Ford Mustang"
730 Great Deals out of 41,499 listings starting at $900
Used Buick LeSabre"
16 Great Deals out of 2,600 listings starting at $1,450
Used Toyota Camry"
1,654 Great Deals out of 99,024 listings starting at $895

Used Cars For Sale

2011 Mercury Grand Marquis For Sale
5 Great Deals out of 44 listings starting at $4,995
2010 Mercury Grand Marquis For Sale
9 Great Deals out of 123 listings starting at $3,995
2009 Mercury Grand Marquis For Sale
5 Great Deals out of 130 listings starting at $2,995
2008 Mercury Grand Marquis For Sale
6 Great Deals out of 204 listings starting at $2,500
2007 Mercury Grand Marquis For Sale
13 Great Deals out of 210 listings starting at $1,993