Dude, where’s my torque?

There are many reasons for a car engine to take longer to start and deliver less torque than it used to, but here are some of the most common ones:


  • Fuel filter: replaced not too long ago, should be fine for another 10′ or 20′ km.
  • Air filter: replaced a couple of months after the fuel filter.
  • Fuel pump: replaced (with an original part) after the last one failed a year ago.
  • Oil and oil filter: replaced twice a year and topped up as needed.
  • Spark plugs: replaced… wait a minute… replaced when? I think I remember buying new spark plugs twice, but I can only remember replacing them once, around the same time as the fuel filter.

Adding insult to injury, the engine has been running hot due to cooling issues that were only recently resolved (I ended up replacing the radiator and expansion tank).

The plugs I used the last time (Bosch Super 4) are now unobtainium, so I got a set of NGK V-Line 24 plugs instead, and installed them earlier today. The photos on the right are of the old plugs, and confirm at least part of my hypothesis, viz. that they needed replacing.

The plugs on the top photo are from the left cylinder bank. From that angle, they look normal except for two things: first, the oil on the third plug, which is of no big import, as it is on the outside end of the plug; and second, the difference in color between the leftmost plug and the other two, which shows that it hasn’t been firing properly (if at all) recently; the spark plug wire was loose.

The plugs on the middle photo are from the right cylinder bank. The one on the left (from the rearmost cylinder) has a certain amount of soot on the ground electrode, but not as much as it looks like on the photo.

The third photo clearly shows excessive ash buildup on the tip of the center electrode and insulators and uneven wear of the ground electrode. As far as I can tell from various online spark plug reading charts, including this one from NGK’s US website, this is consistent with what one would expect under the circumstances.

Old plugs out, new plugs in, start the engine, and it chokes and stalls almost immediately; ask K to listen for unexpected noises and try again; K confirms that there is a strange wheezing sound coming from the area where I have forgotten to reconnect the air inlet hose which was in the way of the rearmost right-hand-side plug. A few minutes later, I’m putting way too much load on a cold engine and tearing up some freshly-laid stimulus-plan asphalt.

Next up: the serpentine belt tensioner—but that’s a story for another day.

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