Changing spark plugs

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Jan 8, 2009
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How advisable is it for the wanna be shade mechanic to change spark plugs on modern cars? Setting aside the fact that they can be very difficult to get to, isn’t there a lot that can go wrong? Since they’ve been there for years and over 100k are they harder to get out than in the instructional video? Risk of stripping the soft aluminum threads or messing up the coil?

Us amateurs only do this once in a blue moon so is it more technical than the old days?
 
It is not difficult at all (if you plugs are accessable). Do use anti-seize on the new plugs before you put them back in. What vehicle are you contemplating changing?
 
Unless you have some odd ones that are known to break when coming out (Ford 5.4 comes to mind), they usually aren't bad. Use a torque wrench going back in and they should come out again nicely. Ditto on what someone else mentioned, check with the manufacturer when it comes to anti-seize. Coil-on-plug ignition may or may not be an issue. Usually just unplug the harness, undo a bolt, and slide the coil pack out. My Traverse fought me on one when a contact spring parted ways and stayed in the well, which then got jammed between the spark plug and the well when I stuck the socket in there. The Pilot was pretty easy, had all 6 done in less than an hour.
 
Coil on plug makes it take longer. Just did my F150 (5.0) at 100K miles and added some NGKs,took me 30 mins
no issues...
 
What specific vehicle are you working on? Changing plugs can be a piece of cake 15 minute job or it can take all afternoon. My Nissan Frontier 2.5 requires the intake manifold to be removed and if you follow the service manual then that will necessitate the draining of a small amount of coolant along with a throttle body relearn when it's all done.

So the job can vary by vehicle make and model. Give us some details please.
 
difficulty varies BUT a good to do as my girlfriends vw passat with 100 thou plugs changed at 50 thou netted 3 MPGs!! like other lifetime stuff its just MARKETING IMO to sell the vehicle. sure they work but like the RDA's for vitamins just enough BUT not optimal IMO!! i have been lookin at the tough side of my V-6 2011 Fronty + others noted its dooable WITHOUT removing the intake $$$ and i will try as i have lots of tools!! + as noted plugs in a LOONG time can be difficult!!
 
It is not difficult at all (if you plugs are accessable). Do use anti-seize on the new plugs before you put them back in. What vehicle are you contemplating changing?
Various manufacturers discourage the use of anti-sieze on their plugs:

Read item #1 in this article:

Some tell you to adjust the torque setting when using anti-sieze, and neither encourage nor discourage its use:


From Denso ... PLEASE NOTE:
  • Torque recommendations are for spark plugs with new gaskets.
  • If using anti-seize compound, use sparingly and reduce torque by 30%.
  • Denso has created their recommendations based on the general consensus of most engine manufacturers. In the case of a discrepancy between the plug manufacturer and engine manufacturers recommendations, always default to the engine manufacturer.
I post these as examples. Check with the plug and engine manufacturers to determine your best course of action.
 
Shel, I will acknowledge your posting about what manufacturers of plugs and vehicles say about using anti-seize. I have also had personal experience in trying to extract NGK plugs that did not have anti-seize put on them as directed. My personal experience is to use it on every vehicle that has an aluminum head......but to each his own as the risk you take is your own.
 
On most transverse V6 engines: impossible
On those vans where most of the engine is under the windshield: almost impossible
On most inlines: very easy

Do the job cold, like first thing in the morning, before the car has ever been started that day.

If your car is one of the impossible engine designs, consider iridium or ruthenium, and replace anything else that might go wrong while you're under there. For example, it is usually a good idea to replace the valve cover gaskets on most transverse V6 spark plug operations, since you're already there anyway.
 
Depends on vehicle. My Silverado? Easy as fudge going through wheel wells.
My Odyssey? The back 3 aren’t that great.

My old Nissan Maxima or Monte Carlo Z34? Fml
 
Modern spark plugs with Iridium electrodes can last almost indefinitely. However, they can fail if the gas seals start to leak. In many cases, the recommended plug change interval is set so that the plugs will be replaced before any gas leakage begins.

The thing to avoid is damaging the threads in the cylinder head. Sometimes, depending on the engine, getting the new plug started in the thread is out of the mechanic's sight line, done by "feel". If its not starting in the thread easily, be careful, try again.

Its not like the old days when a set of plugs in a high performance engine was good for maybe 6000 miles. Fuel injection and modern ignitions are a great advance over carburetors, leaded fuel, and points and condenser, distributor cap ignitions with iron core plugs.
 
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You are correct about the many problems that can happen. The threaded portion can break off in the head, and some times it can be removed and some times the head needs to be removed to remove it. I have used anti seize on spark plugs and have had it harden up and act like a thread locker, so do that at your own risk. The simplest jobs can be the most difficult some times. Good luck
 
It depends. I've been changing my own sparkplugs for years and never had an issue until this year on a very easy 4 cylinder 94 Cavalier. The plugs had been in for around 100,000 miles and two of them did not want to come out. One eventually did and the other broke off inside the head.

It took a heavy duty impact and an easy out to remove it but it did mess up the threads a little bit. I was able to clean up the threads and get a new spark plug in it and it's been fine ever since.

All of our current vehicles are four cylinders or V8's so accessing the plugs are all fairly easy. The 3800 powered 2004 Monte Carlo SS that I owned was a bear to change on the back banks against the firewall. For some vehicles it's a pain in the rear and may not be something someone wants to tackle.

As far as using anti-seize on spark plugs, I never do.
 
As far as using anti-seize on spark plugs, I never do.
Maybe if the last person to install plugs did, you wouldn't have had this problem
never had an issue until this year on a very easy 4 cylinder 94 Cavalier. The plugs had been in for around 100,000 miles and two of them did not want to come out. One eventually did and the other broke off inside the head.
 
Maybe if the last person to install plugs did, you wouldn't have had this problem
I was the last person to install the plugs prior to that and two of the plugs came out easy as can be. I've owned a 92 Cavalier with the same engine since 2006 and have done several plug changes over the years and have never used anti-seize and have never had a problem with the plugs coming out. Anti-seize does not guarantee easy removal. I've had a hard time removing O2 sensors that I've installed that came with anti-seize on them that didn't want to come out.
 
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