Replacement of spark plugs
 

1998 Mercury Grand Marquis
Location: Zip code 33027
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I want to know the cost of replacing spark plugs (material and labor) as I believe I was overcharged at a local shop.

Please advise.

I was quoted $600 for a diagnostic and tune up which involved replacing the sparkplugs. I thought they were crazy so I did it myself. After finishing, I realized why they charge so much. It isn't very difficult but you have to remove the fuel rails and I damaged two of the injector O rings in the process. You might even consider having replacements on hand if you are going to do it yourself.

You can find a shop to install new plugs for under $150 if you shop around

Replacement of spark plugs
 

Thank you so much for your information.

I did my cap Rotor and plugs And wires, and (parts) were $78, and OEM parts ....
I did all work my self. in 1 hour, taken my time.

I just did mine and it was easy. The boots are so flexible that you do not have to remove the fuel rails at all.

Copper, iridium, or platinum? Has anyone noticed a difference in mileage or performance with replacement spark plugs or is it simply a matter of how often you have to replace them?

On that model year Ford used a 2-part spark plug that tended to break off in the engine, many dealers don't want to touch them. That's why the price is high, they are a pain.

Plugs? Just changed a set of factory installed Iridium's on a Kia Sorento that had 100K miles on them, and they looked like new. I plan on using them on my next '03 Marquis change out.

Spark Plugs '92 -'10 Grand Marquis
 

The best type and part number for the 1992 - 2010 Grand Marquis is the BOSCH #9606, which is a Double-Iridium type that is superior to the OEM platinum type that's fitted at the factory, and it has exclusive features that other plugs just don't have.
Currently available at ROCKAUTO.COM for $5.02 each.
I have used these plugs in my '95 Grand Marquis restoration project car, with excellent performance and fuel economy, regardless of altitude and/or outside air temperature.
Silky-smooth idle, excellent throttle response, and excellent fuel mileage on 87-octane gas (with 10% ethanol).
If you have the twin coil packs, replace the ignition wires with Bosch Premium Mag-Core ignition wires.
I got my wires from Amazon.com.
When changing plugs and wires, it's a good time to remove and inspect the coil packs for carbon tracking or other problems.
Test the coil resistance with an Ohm meter.
Should be 0 to 1 Ohms for the primary - (lower is better).
14.5 Ohms is ideal for the secondary.
If coils test good, spray them with WD-40, then wash them thoroughly with soap and water.
Spray the terminals with WD-40 before re-installing the coils.

When done right, your ignition system should be trouble-free for 75,00 - 100,000 miles.