2009 Kia Sedona 3.8 - spark plugs @ 120K km

[Number_35]

I guess the title says it. Changed out just the front bank so far; as is typical of transverse DOHC engines, the intake manifold needs to come off for access to the rear bank.

I'm pleased with the condition of these plugs. The van runs fine; did these only on the basis of age and mileage. Replaced them with same, which per NGK are rated for 120K km.

 

[Kamele0N]

The one in the middle was tightened too much when installed...thats the reason why insulator is brown (metal part/nut skids on an insulator and allows combustion gases to escape in between)

 

[slacktide_bitog]

When you do pull the intake to do the rear spark plugs, you may also want to replace the valve cover gaskets, too

 

[Number_35]

Interesting! If so, that would likely be my fault, as I pulled one about two years ago to see whether I thought they'd be last to the recommended interval.

 

[Number_35]

Good thought! That would allow for the coveted "valve cover off, here's what it looks like after 25K km on Mobil 1" photos.

I'm changing the plugs in part because of the discussion a week or so ago about how old plugs have a wider gap requiring higher firing voltage which leads to premature coil failure.

 

[Number_35]

OK, so this is just (pleasantly) weird. As you can see in the original post, the plugs don't look bad at all. The engine was smooth, and always started well. I changed these three plugs purely because they were at the end of NGK's recommended maintenance interval (120K km) for the OEM iridium plugs, not address any sort of issue.

In the 2 yrs plus we've had the van, it's consistently done 11 l/100 km on the highway. This is per the ScanGauge, I haven't crunched this based on actual fuel taken on, but it looks pretty close (that is, I would fill with about 55 litres after 500 km).

We just did our first road trip with the new plugs. (Bear in mind only 3 of 6 are new). The ScanGauge was consistently indicating mid-8s to mid-10s depending on our speed. That again seemed consistent with the refills, but I was doing head-crunches on US gallons into litres, so I might be mistaken. But regardless it's the same ScanGauge, so the relative results should be valid.

I'm eager to get to the rear three plugs and see what happens. (For what it's worth, Transport Canada rates the van at 8.x l/100 km, so perhaps the new plugs are only taking the fuel consumption back to what it should be.) If this is so, I'll keep an eye on the plugs and change them out sooner next time.

 

[clinebarger]

Not really surprising, Some engines are easy on plugs! LSx engines are known for getting 200,000+ out of a set of Iridium plugs in demanding applications.

 

[Number_35]

OK, I pulled the intake manifold this afternoon and changed the plugs in the rear bank. I was working with the van backed into the garage, with the garage door open for light. The garage lights do not throw enough light for my old eyes to do fine work like this, so I packed it in after getting the new plugs in. I hope that I can finish up in a couple of hours tomorrow. The new photo uploader doesn't allow us to preview the post, so the captions may not line up with the photos. You BITOGers are a smart bunch - I'm sure you'll figure it out!

Here's the top of the engine with the intake manifold removed:

Here are new and old plugs side-by-side for comparison:

The intake ports are blocked off with paper towels, mostly for my peace of mind:

Here are the old plugs. All were in spec - a 0.040" wire gauge could pass, and a 0.045" couldn't:

 

[Number_35]

Got it all back together this morning without much drama, and with no leftover bits.

The engine started well (seemed to be better than usual, but perhaps that's my imagination) and a test drive seemed to yield improved drivability (although that too may be my imagination). No issues with it before other than the high fuel consumption, but it seems to drive a bit better now.

If this plug change does result in significant reduction in fuel consumption, I'll change out the plugs earlier next time. Kia says 160,000 km, and NGK says 120,000 km, but there's no way I want to wait until they're wasting fuel.

The job took me about four hours. I think I could do it in < 3 hours now that I know what's involved.