Keeps blowing spark plugs, all plugs have been changed

Asked by Sep 16, 2017 at 10:28 AM about the Mercury Grand Marquis

Question type: Maintenance & Repair

2002 grand marquis

11 Answers


What do you mean by 'blowing spark plugs'? Do you mean they are fowled out (wet or very black)? How many miles on the engine? A high mileage engine can fowl plugs due to oil leaking into the cylinders (worn oil rings) or a fuel problem can cause it by too much fuel or not enough air flow (blocked filter). You may need to do a compression check of the cylinders to determine the health of the engine.

2 people found this helpful.

No oil on plugs. Check engine light on and engine thugs in idle. Also the OD light is out too ? Brought to AutoZone to check the codes and stated spark plugs #8 and #7


You don't give a year for your Marquis, but if it's more recent, check the coils for those plugs. Check also wires and cap/rotor, you may have something like arcing especially if cap/rotor is worn or allowing water to get in. Even hairline cracks invisible to the eye can cause problems.

It's a 2002 grand marquis


Agree with Ken, check the plug wires and cap/rotor. If they look good then a compression test of the cylinders would be the next step.


There is no cap and rotor or wires with a Triton engine.


When someone says they are blowing plugs on a Triton engine it usually refers to blowing the plugs out of the head. If you have a misfire you probably need new coils.


You probably have a couple of bad coils or plug boots. You can swap them around to another cylinder to see if the miss moves. Also Motorcraft brand coils will be the best quality for your Mercury, but they do cost more.


What the person saying is the spark plug blew out of its threads and shot away from the engine, in their 2002 car, a high number of these cars do this around 150,000 miles- why

2 people found this helpful.

I just had the same promblem on my 2003 grand marquis. It vlow out the spark plug . And by that i i mean it blow the plug out of the hole treads whe streped out to .


The 2002 4.6 engine had only 4 threads in the spark plug holes. If plugs are replaced and not properly torqued the threads can be damaged and spark plugs can be ejected from the cylinder head. A proper repair is not cheap.

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