Kia Carnival KV6 Spark Plug Replacement

I have a 2004 model 2.5l Kia Carnival (i.e. with the Rover-designed KV6 engine).  I’m not a mechanic, and wouldn’t even call myself a backyard mechanic, but I like to do what I can.

The vehicle was due for new spark plugs (overdue actually - they were due at 90,000km, but it had 103,000km on the clock before I got around to it).   

The three left-hand* sparkplugs are easily changed (and not discussed further here except for some general tips below), but I had read on the net about the challenges of accessing the right-hand* plugs as they are up against the firewall.  Changing sparkplugs is something I had always done since buying my first car more than 40 years ago and I wasn’t inclined to start paying someone to do it now!  So I decided to give it a go and found it’s really no great problem to do.  So I thought I would write up my experences for the benefit of others.

The surge tank (as its referred to in the Kia KV6 workshop manual) does need to come out to gain access to the RH plugs from the top but that was not a difficult job.   I read a suggestion to drop the engine down by loosening or removing the No. 3 engine mount but I found I didn’t need to do that. 

All that’s required (aside from the usual socket set, pliers etc) are two ½” drive universal joints.  And a 5/8” spark plug socket with a rubber plug retainer in good condition (but not too good! – see Tips below).

Replacing the plugs with platinum tipped ones means you won’t have to do this job again for 90,000km.   As mentioned, I ran the original platinum plugs to 103,000km, and they were in remarkably good condition (especially given that this is a ‘lost spark’ engine – the plugs fire twice on each cycle). The nominal gaps of 1mm were only about 1.1mm, with only minor ‘dishing’ of the earth electrode.

I bought NKG PFR6N-11 plugs (which is the same part number as the ones I took out) from Bursons - $120 for the 6.

I replaced both ignition harnesses at the same time, as someone suggested (reasonably) the insulation & rubber would be getting tired and hardened after 90-100,000km.  Bursons wanted $140 for aftermarket harnesses, but my local Kia dealer only wanted $126 for the genuine ones, so I bought those.

The surge tank (Kia term, Rover call it the inlet manifold chamber) is bolted to the inlet manifold proper, and the throttle body is bolted to the tank.  Here’s a photo of the surge tank before removal (with the engine’s acoustic cover removed) showing what needs to be removed: 

The two bolts securing two brackets on the tank to the camshaft cover need to be removed by feel, but that's not too hard.

When easing the surge tank off the inlet manifold, there are o-rings on the short pipe extensions on the inlet ports for the RH cylinders that will provide some resistance for the first 5mm or so.  Be careful prying the tank off, don’t damage the gasket on the LH cylinder ports.

The surge tank and inlet manifold runners will show some oil contamination from the crankcase breathers, and this is an opportunity to give them a clean.  I also took the opportunity to clean some of the accumulated oily gunk out of the throttle body and off the throttle butterfly.

Here’s the view once the surge tank is removed.  The RH cylinder bank camshaft cover is now visible.  The spark plugs are just on the other side of the cover. You don't really get to see them (unless you have a dentist's mirror), you need to do everything by feel:

Cover the inlet manifold ports with a cloth to keep dirt & foreign objects out.

Reach over the camshaft cover and pull the plug leads off - if they are like mine, and not touched since the vehicle left the factory 100,000km ago, they will need some pulling & twisting and there's only just enough space between the engine and firewall to get them out of the spark plug recesses - particularly the leftmost one.

Use two universal joints and the 5/8” plug socket onto your socket wrench like so:

The combination of the two joints (each 75mm long in my case) and the socket (65mm long) gave exactly the right length of ‘extension’ to reach around the camshaft cover & get down the spark plug recess to engage with the plug. Snake this assembly down into the spark plug recesses by feel, undo the old plug and retract.

Do the reverse to install the new plugs.  The feel on the wrench is a bit sloppy from the double dose of lash from the pair of universals, but there is no real problem feeling the plug washer hit the face and tighten.

Inserting the plug connector for cylinder #2 (leftmost) was the trickiest, as some air-conditioning pipes on the firewall were in the way.  This was the only time that a few more millimetres afforded by lowering the engine would have been useful.  Nevertheless I found that, by holding the plug connector with the spark plug connection end uppermost, and bringing the connector up in a gap between two of the pipes, it went in with a bit of jiggling and compression of the acoustic material on the firewall.

I didn't bother replacing the surge tank gaskets as they were in good condition.  Reconnect all the hoses, the brake booster vacuum hose being the most critical of course - double-check its security.  The pesky little air hose under the throttle body is easily pulled off while you are positioning the harnesses, etc.  Have done 4,000km since the change and no problems.

Tips

• Use platinum tip plugs – I used NKG PFR6N-11 (and these were the original part).

• Replace the plugs only when the engine is cold.

• It’s a good idea to change the ignition harnesses at 90-100,000km.  $126 for genuine Kia harnesses (RH and LH).

• Don’t over-torque the plugs in the KV6’s alloy heads!  If uncertain, use a torque wrench. (Torque: 18-22 ft/lbs, or 25-30Nm, or 2.5-3.0 Kg/m).

• The box that the NKG PFR6N-11 spark plugs come in has a diagram suggesting to tighten the plug ½ to 2/3 of a turn after the washer contacts the face – this would be only if the washer on the plug is un-crushed (i.e. the plug has not been inserted and tightened before).  Again, if uncertain, use a torque wrench.

• Before inserting the new plugs, it’s a good idea to test the assembly of socket and joints by inserting a spark plug into the socket and pulling it out - make sure the rubber retainer in the spark plug socket ‘lets go’ before the ½” drives on the universals do.   Otherwise the spark plug socket may stay in the hole when you withdraw the assembly after tightening the plug.  (One of my universal joints is an ancient thing - the ball detent was pretty tired and was letting go first – some oil on the ball detent fixed it).

Any comments & suggested additions are welcome!

* On an ‘east-west’ engine layout, the ‘side’ of the engine is referred to as if the engine was ‘north-south’.  So the ‘LH’ side of the engine is the one to the front of the vehicle, and the ‘RH’ side is the one to the rear, against the firewall.