Thread: OT - How Often Should You Change Sparkplugs on Modern Engines

So I was driving in heavy traffic yesterday with 2000 pounds of parts in the back of the truck and it was 108 degrees outside. I noticed that sometimes when I stopped the engine would run rougher than usual (2005 GMC with 5.3L V8 with 94000 miles). It then dawned on me that all I had ever done to it was change the oil as scheduled and changed the air filter once after a very dusty hunting trip. Any idea how long they should last and anything else to look at?

What does the Owner's Manual recommend?
Electronic ignition systems and platinum/iridium electrode plugs are good for quite a few miles, but I'd bet 94K
is just a little excessive.
You might want to do the air filter as well as a fuel filter.


Rex

Could just be bad gas, if it was an ignition issue it would throw a code and the check engine light would come on.
Sounds like an over due tune up / maintenance is in order at the very least.

Tom

Most of the Benzes I work on now call for 100,000 or 4 years, sometimes there is a problem at 85K and they get replaced, the most was 168K ---by then the special alloy inserts in the ground electrode were gone along with much of the ground electrode ---and the coil from forcing a spark through the twice the normal gap.

On an engine with plug wires it is good to replace wires too, on a coil over system I like to replace the "connector"---this way the job is done 1 time and should last for the next 100,000
A fuel filter is a good idea, and if it has one the cabin filter is often overlooked---many of these get more dirt in them than the engine air filter, i believe that when the cabin filter is clogged the reduced airflow and higher amperage needed for the blower trying to suck air causes premature failures of the blower and controller

Engines that use some oil will get shorter life out of the plugs due to oil ash deposits.

If it has any easy ones, I would pull a couple and look at them, I have pulled them at 100k that looked like they would run another 50 easy.
James

IIRC you're supposed to check and regap the older plugs every 30k and replace at 100k. My new(1991) chevy pickup only has 66k and the plugs haven't been touched.

I have 212k on mine. oem replacement for a gm 3.8, might want to check the wires at night though.

120000 km (75kmi) for Subaru with platinum plugs. Plugs were still looking ok. Same service interval as timing belt.

You could do the equivalent of a dealer service, pretend you've changed the plugs and tear up some money!

With electronic ignition, there is no problem with spark even if the electrode is mostly gone, it is just insurance against the plug shattering and causing subsequent damage.

Federal pollution laws require an engine be able to pass the emission test after 100,000 miles with no work other than fluids and filters as recommended.

I put 140,000 on a Chevy 4.3L before changing plugs and wires. Mileage hadn't dropped and didn't improve with the new plugs. Same engine as yours, just 1/4 shorter.

Spark plugs go for a long time nowadays...

On my '01 Pontiac 3.8lt I do it earlier than recommend, but I usually use NKG Platinum tipped, yes they cost more but compared to the car their cheap...

It could be the quality of the fuel on your last tank, a lot of sediment settles in the fuel storage tanks at the station...

If you have a habit of getting filled up anywhere it could be a possibility that your fuel filter is partial clogged but you would more likely notice a power drop rather that rough running...

It could be heat soak of the engine after shutdown, quite often the engine temps will become considerable higher because it continues to reject heat into the cooling system and had has nowhere to go...

Heat soak is more likely after a longer shutdown rather than a few minuets or an hour or so, during the former little heat is rejected as opposed to a longer period when the heat is rejected to the atmosphere (cant think of another word)...

If you notice that there is no problem running after a short shutdown or considerably longer time period this could be a problem...

I'll check this thread later on.

If air intake is in a poor location, (over core support) this could result in roughness.
107° ambient could be close to 200° in engine room.

if it is a Ford with a Modular engine, you install new ones when the olds ones blow out of the head!

I usually at least take them out every 25,000 or so. I have seen them seize in the head when they were not removed until there was a problem. I always use anti seize on them when they go back in.

my wife's ford escape recommends 100,000 on the plugs. About 85,000 on them and just passed smog at about 10% of the allowed co etc so i would say they are running well. over 100 F I would suspect detonation from carbon deposits in the engine, was humidity low? water injection does help at high altitudes. I have seen heads that cracked and the water leaked into the cylinder, steam cleaned the carbon in the one cracked head.
Bill D.

Manual for my 2002 Chevy Silverado says change at 100,000. I only have 26,000 on it after 10 years, so I haven't. Engine seems to run fine.

The new precious metal spark plugs they make today are really good.

Just for comparison sake, if you ran 60 MPH, 24 hours a day, it would take about 1700 hours to go 102,000 miles, (about 71 days).

The natural gas compression engines we run go about 2000 to 3000 hours, (about 80 to 120 days) on spark plugs depending on the engine and the load. These are big Cats and Waukesha 12 cylinders for the most part averaging between 1500 - 1800 HP. The ones that are humped up hard around the clock get the shorter end of the plug life.

The generator set engines we run at one of the plants go 6 months, about 4,300 hours on plugs. These are Waukesha 7042s, but aren't running 100% load around the clock. Probably loaded 75% - 80% most of the time which would be a little more comparable to driving 60 MPH.

The rough idle could be something related to the air conditioner compressor cycling in or something along those lines.

Modern engines have spark plugs?

Yep and on some of the smaller natural gas compressors I have been seeing as much as 1 year out of platnium plugs.

Spark plugs in a modern engine are lifetime parts in my opinion. I changed the plugs and wires on my 5.7L Tahoe at 200,000 miles and made it worse! I didn't have radio noise until I changed the wires. I checked the gap on the plugs and they were worn about .002". I was afraid that they would gall in the heads, but they came out very easily. I'm up to 371,000 now.

My 5.3L Suburban has the original plugs in it at 195,000 and they're not going to get replaced.

I have them changed at 100k, but will not change them myself. $70 at the local dealer is much cheaper than having a plug break in a head, and with "modern" plugs and engines it really is a tossup IMO. When I was still turning wrenches for a living I saw many engines that had relatively low miles (<50k) in which the spark plugs would break or strip in the head regardless of how careful a mechanic was. Plugs are getting better longevity yes, but with a combination of cheaper materials/threads and hotter engines, I believe modern plugs are more likely to get stuck.