Part of what makes something more expensive is quality control. Cheap parts have very little quality control so you are likely to get a bum part. If you bought 10 I would expect some to bad out of the box and others to go bad prematurely. For me it comes down to is it worth my time to replace this part if it goes bad prematurely? The answer is usually always no so I buy the more high quality part so I don’t have to touch it for another 100k miles.

Maybe neither.

What do you mean?

Missing, or inop/dead/numb/no-fouler installed?

Depends on how the engineers programmed the original control unit and the strategies they intended it to use.
One design may be affected minimally if a sensor is numb, another design may be greatly affected.



If a TUNER is doing it and they can't make the processor ignore the rear sensor input....what does that say?


Cat monitoring may have been an original design intent while OBD2 was being dreamed up and hammered out, but that's not the only thing going on.

Engineers design these things with emissions control FIRST, the idea that the first function of the engine and all fuel controls is a life support system for the catalytic converter. The engine just happens to pull the car around in the process.


Rear sensor can have a lot of influence over fuel trim values and strategies. The newer the car, the more important it is.

Even a cat fault code can cause a large drop in fuel economy on some cars.

My 2005 Civic is missing the downstream o2 sensor and has no cat. If I get a junkyard downstream o2 sensor and install a defouler, will the car run better, worse, or no different?

If it works fine that way for you and you're ok with the CEL on all the time, DFWI.

Probably no real noticeable difference in how it runs, but the ECM or PCM will continually attempt to run the cat monitor self testing as long as there is no fault code for either O2 sensor....
Do you know how that cat testing is done?
By manipulating fuel controls.

until they don't work anymore.

The questions are:
1) How suddenly would you like it to go?
2) Would you like to have an upper mount go in a strut type suspension?

I tried the same setup with a 6th gen I owned a few years ago. I used two spark-plug defoulers piggy-backed as described in this thread: https://dodgeforum.com/forum/2nd-gen...t-removed.html .Had car for 10k miles afterwards and the CEL never came on again for secondary o2 code.

Didn't seem effect performance in any way.

I know that I can put D17A7 (CNG) pistons in my D17A2 block to increase compression to 12.5:1, but I don’t think that anyone actually tried it on 93 octane pump gas. I Can use use 93 octane gas, but I’m not sure that 93 octane is enough for 12.5:1 compression. So my question is will it work? I really want to try it, but I don’t know what would happen, which unfortunately makes me want to try it more lol. I think it would either work great, or knock and not work. Also, IF it did work, would I gain a noticible amount of power? What do you think about this?

My 2005 Civic has an ECU issue and needs to be replaced. I can get a junkyard ECU for $23, which I can afford. The problem is that Honda wants $110 to flash it. My question is if there is a reason why I couldn’t get the ECU and key from the same car and swap the immobilizer chip in the key. The only thing that keeps it from starting with a replacement ECU is the immobilizer, right? Would this work?

I think if your gonna start messing with radical changes to the engine, your going to need a standalone ECU such has Ktuner (the experimental one im running) or Hondata to adjust fuel maps and timing.

What would happen if I don’t?

Why wouldn’t the knock sensor protect the engine?

How are you gonna dig that thing out without damaging it? Besides, you need the immobilizer control unit on the column lock to match the ECM and keys too.


Some people just get the entire immobi/ignition/steering lock assembly with the keys that all match the ECM. Then you get to deal with the extra keys needed on the keyring

Jet fuel is in the 100+ octane range, isn't it?
Octane and timing aren't the only factors that lead to or prevent detonation

Or you swap all the lock cylinders to match the donor ignition cylinder. But, you would still want to have more keys programmed since you would then have a car that you could not ever have the key cut off of VIN. Changing the ignition lock to something that doesn't match the cars original key code has the potential for big problems in the future. Lose all the keys and you aren't getting a key cut/programmed, you would be getting a new lock cylinder again.

I've taken out the "chip" part of an immobilizer key on my 2002 before. There is no non-destructive way of doing so. Thing seriously looks like a little wannabe lightbulb. It just confused me even more of how it all worked.

Had a 4th spare key laying around so I decided to see if I could mount the chip somewhere close to the key slot and see if it'd work. Long story short: it doesn't. If that thing isn't oriented just right, it won't let the engine fire up. I'm talking even fractions of a milimeter angled or spaced wrong and it wouldn't work. Only when I put the wannabe lightbulb thingy back in it's silicone sleeve in the proper orientation on the key itself, and made sure the spacing within the silicone sleeve were absolutely perfect, then the engine would fire up.

Isn’t E85 105 octane or something? That would certainly be enough. If I could afford to convert to it, which I can’t. Jet fuel and race fuel is not an option.

My 2005 Civic VTEC misfires on all cylinders when it’s cold. It misfires mostly under load. Once the engine warms up, it seems to run fairly well, but I’m afraid to push it. Even once it warms up, the engine feels fairly unresponsive and low on power, but it doesn’t misfire. It feels like the more I try to accelerate, the more it bogs down. It’s acting like a bad fuel pump, but I replaced the fuel pump and filter about 2 years ago as preventative maintenance, so I don’t think that the fuel pump is bad. I swapped the MAP sensor, cam sensor and crank sensor with extras that I had, which made no difference. I have had issues with the junkyard D16Y8 fuel injectors that are in it about a year ago, but it seemed to run fine after I cleaned the fuel injectors until now. I wonder if they are having problems again. I checked for vacuum leaks, it doesn’t have any. It has no cat, so that’s not the problem. The only (new) codes stored are P0301, P0302, P0303, P0304 and P0300. I am thinking that I need to do a fuel pressure test again and see if the fuel pressure is significantly dropping when the engine is under load. Any other ideas? Thanks.

Got good spark? Compression good, too?

I doubt that all 4 coil packs would go bad all at once. Also, I didn’t do a compression test, but the compresssion sounds good when cranking it. I removed and rebuilt the engine in it about 8 months ago, so I presume that the compression is good.

Did you learn all about stoichiometry yet?

How much more fuel (injector) delivery do you have to have available in order to safely run E-85 without going too lean??

I know that I don’t “need” head studs for my D17A2 unless I’m boosted, which I am not. But would there be reliability benefits if I installed head studs? For example, would engine damage, such as a warped head or blown head gasket, be any less likely if the head is held on with head studs instead of bolts?Are head studs only for high performance engines, or could my daily driver Civic benefit from them too? Thanks.

Could be more than coil packs. Spark plug gap and electrode wear have roles in spark, too

Also, compression could sound good, but could be off. First time I had a blown head gasket, only thing I noticed was intermittent misfires and coolant temp rising with a/c on at low speeds. Compression test showed something like 210-185-205-215, cylinders 1-4, respectively.

Wait, whut?

None IMO.

So the head and head gasket won’t be any less likely to be damaged if the engine overheats?

The ONE thing I always thought would be a tremendous improvement is a set of TTY head bolts......but I've never seen any the right size for this application

No.

TTY head bolts MIGHT make it just a little more robust, but I've never seen any for this engine.

Overheating can trash just about any engine quick.