Guess where the compression went

[RacinBob]

A brief update from the shop of cousin Anthony.

The Camry engine is back together and back in the car. #2 cylinder went from 0psi to 190psi. (196psi is spec). Rest of the cylinders are all above 180.

I'll hopefully have her running again today.

To install the timing chain, you have to compress and reset the tensioner which buried down the side of the engine.

The tensioner Pretty ingenious. A little hook holds the tensioner plunger in. Turn the crank in reverse, then forward. Tensioner plunger pops right out.

The intake manifold rattled when I shook it. Hooked up shop air and blew out a chunk of the intake seat. Took the manifold and hosed it out with soap and water.

I cleaned the piston crowns up with a Dremel and a flapper wheel. Turned out really well, but I lost the photo when my phone died.

The biggest pain was removing and reinstalling the power steering pump. Its really jammed back there.

[Old Busted Hotness]

Am I the only one who's bothered by the O2 sensor placed in the #3 header rather than in the collector?

[A Former User]

@old-busted-hotness Nope. Seems really odd to only have it monitor the the output of one cylinder. When I installed the fuel injection on my El Camino they made a big deal about the fact that the O2 sensor needs to be in the header collector or within 6" of it in order to get accurate results.

[RacinBob]

Oh, I am not sure what the sensor does for him anyway. I don't think there is a converter on the car. Also the CEL has probably burned out by now.....

[Old Busted Hotness]

I'm guessing they set it up that way so you can use the stock sensor and wiring.

[A Former User]

@old-busted-hotness I would think the O2 sensor would still be needed to do things like tell the computer how much fuel it needs? I assume this is the first sensor as opposed to the not-really-necessary downstream sensor after the cat. My guess is in it's current position it won't do much good.

Or maybe I am reading the whole thing wrong and this is exactly how it's done.

[aremmes]

It doesn't seem so strange to have the O2 sensor on an exhaust runner when you consider that there's only one MAF/MAP sensor on the intake side, so it's safe to assume that all cylinders get roughly the same amount of fuel and air per cycle. There are other ways to detect per-cylinder problems through the ignition system and knock sensor.

[A Former User]

@aremmes I'm sure they do get roughly the same amount of air/fuel mix. I am also sure that the O2 sensor is not meant to be 8" from the exhaust port on the engine - at least 24" downstream seems to be the common placement. Positioning the sensor too close to the exhaust ports can expose it to high temps as well as over-cooling from the high-velocity exhaust gas flowing over the sensor.

[aremmes]

@sovande Don't tell Honda that.

It's actually pretty common to place the O2 sensor very close to the exhaust ports. My 2000 CA-spec Miata has the upstream sensor within 8" inches from the ports upstream of the also-very-close warmup catalytic converter.

[A Former User]

@aremmes Interesting! Maybe it's more important for older cars or cars with larger displacement engines? Honestly the only thing I know about it came from reading about where to put one on small block Chevy and guessed I assumed (wrongly) that most cars would be similar.

Thanks for learning! Or the teaching!

[aremmes]

@sovande I suppose it all depends on each individual engine design. With today's engines with integrated exhaust manifolds, the exhaust is cooled before leaving the engine by virtue of being surrounded by coolant. There may also exist some O2 sensor types that don't do well with excessively high temperatures, but even the cheap one-wire sensor used in the BG Protegé I had at one time wouldn't work right until it had warmed up (and also had it placed very close to the head), and modern four-wire sensors actively heat the probe to get them working more quickly.

[Old Busted Hotness]

Physically that's where it belongs on a 4-cyl Camry, but it's supposed to have an iron manifold and a cat. The O2 is at the flange where the cat mounts (upstream of it). I'm sure they put the bung there so the sensor would just go in without having to extend the wires (which can alter the reading). It's probably fine, just... not right.