I’m at about 150km (nearly 100k miles) and I decided to replace the coils with hitachis. I was getting some rough idle with AC running. I did the valves at about 40k miles ago so I’m probably gonna recheck/readjust them soon. I’ve been having issues with loose plugs; this time it was no. 4 that wasn’t event finger tight. While the plugs were out, I snapped some pics of the piston crowns with my borescope. I was surprised of the carbon buildup in there. There also seems to be some slight scoring of cylinder 1 and 4 wall and an odd circumferential gouge in the cylinder 2 wall.. Sorry about the bad angles, it is hard to keep the camera straight when reaching around the back of the engine.

im thinking of running two tanks of redline fuel system cleaner to try and clean it up. What do you guys think? Also, if I run the cleaner, am I supposed to change the oil after since I presume that carbon deposits will be in there?

i also regapped the plugs and and snapped some pics of the plugs and coils and can post them if anyone is interested. Cheers


Cyl 1

Cyl 2

Cyl 3

Cyl 4

 

Thanks for sharing.
This much carbon build up is normal.
The vertical score marks are the reason for ticking noise (piston slap ) many owners are complaining about (aluminum engine)
Have you used anti seize on the plug threads at first replacement? You should not (even if manual says so)
Can you snap picture of the coil from the lose plug.
On my car plug 4 came out easy once broken loose, #1 plug thread was a bit tighter (had some carbon on it)

Cylinder#4 is on the left; plugs had 101k on them (I've changed #2 and 3 at 66k)

 

I would've guessed that the piston skirts would slap the front or rear of the cylinder bore. The scoring in those photos show it on the left or right side of the bore, right? Or does that arrow not point forwards?

@OP - out of curiosity, does it burn any oil?

 

Arrow points to the timing chain so the scoring is on the side parallel to radiator. This scoring is very common on Hyundai engines
Sadly Honda = Hyundai today!

 

My engine doesn’t burn oil at all. I think I’ve topped it off once for being ever so slightly low since I bought it in 2012.

 

Picture of the plugs/coils please!

 

Sure. Cylinder 4 coil (loose plug) was all sooty and the rubber gasket at the top (near to the electrical connector clip) was pulled down around about 1/3rd of its circumference. I suspect that during the intake stroke or during engine braking, over time due to the loose plug, the gasket got sucked in partially. The plug was also blackened. I’ll put a picture of cylinder one plug and coil for comparison.



Cylinder 4 plug (completely loose)

Cyl 4 coil


Cyl 1 plug (normal)

Cyl 1 coil (normal but replaced)

 

Not sure if loose plug has to do with improper torque, of out of high clearance threads in the head. I saw 2002 accord with recently changed finger tightened plugs (gasket was not even crushed) but there was no leakage past them. Same on 87 Camry.

 

I've had that problem once before. If I recall, it was the no 3 cylinder plug that time. Luckily I heard it because of the sound and tightened it; it sounded like a piezoelectric lighter in a barbecue or a gas stove (heard even with the hood closed). Last time I did the plugs, I didn't have a proper torque wrench that did low torques. I think i cheated and used the screen on my torque adapter to set the torque. The lowest value it could beep at was 20 lb*ft. Now I have a dedicated torque adapter that does 5 to 80 lb*ft.

This time I've torqued all the plugs to spec within +1 / - 0 lb*ft. I think it was 13 or 15 lb*ft... whatever's in the service manual. I did put a small amount of anti-seize though. I plan on taking the plugs out again to do the valve lash since its probably hard to turn the engine with the plugs in. I might check the torque then to see if they loosened. I'm not too afraid of messing up my torque adapter by using it to loosen plugs.

So should I try and run a bottle of Redline complete fuel system cleaner? Can't hurt right? What concentration should I run? Is a full bottle too much for the Fit's puny gas tank? My biggest gripe about my Fit is that I only get about 20MPG in the city. Then again, I always accelerate briskly because I don't wanna drive like grandma. I get about 35+ MPG on the highway.

P.S. Thanks Dr. J for your insight. As you can see, I have little to know experience in engine maintenance/tune up so I'm always looking for suggestions.

 

The engine is easy to turn even with plugs in (at least on my car); a lot easier than on 1992 Camry (2.2)
I use old school method (1/2 turn after plug gasket touches the bottom of the spark plug well) the trick is to make certain that the surface around the plug hole is clean from dust and similar materials so the gasket will crush against the sound surface otherwise even compressed and tightened correctly, it will allow gases to pass into the spark plug well and stain the coil (saw this on the junk yard)
Low fuel economy may [sometimes] be caused by aging air fuel mixture sensor (in exhaust manifold); it usually reads normal mixture as slightly lean and adds extra fuel (shows higher CO compared to the car with properly working A/F ratio sensor when checked with 5 gas analyses with dynamometer at 40 km/h cruise)

 

Not disagreeing with you doctor J, but it sure is hard to get your eyes on those spark plug holes — at least it is on the GE models. Sometimes, it seems like good old Honda did everything they could to make this great car impossible to work on. And I say that as someone who does oil, oil filter, coolant, valve adjustments, brake pads, brake fluid, clutch fluid, MT fluid, air filter, spark plugs, battery replacement himself. Sometimes, just to relax, I read the "I can't remove/install my axle" threads.

 

Even on GD3 I had to use mirror and spot light to inspect bottom of the hole; GE is a lot more challenging!! (as well as Toyota or Honda V-6, rear bank)