Civic VX 26 MPG!!!

[nwrubicon]

update: so I went to set the timing and ran into a stupid issue, like a ton of other d series, a valve cover bolt sheared off so I had to take the number 1 and 5 cam caps out and drill and tap them for a helicoil in each...that was stupid, at the same time I checked the valve lash and found that 2 exhaust valves were slightly tighter than the .25mm allowable tolerance so I set them to .25mm. I also did an oil change, reset ignition timing, checked for vacuum leaks using smoke and I failed emissions again.

This time was slightly worse for HC yielding 794 ppm with an allowable limit of 400 at idle. HC was also high at 2500rpm but not as drastically high as it was at idle. CO% at idle was also slightly elevated at 3.5% with an allowable limit of 3.0% so that improved slightly but not much.

so to recap, I've replaced plugs, cap, set cam timing, set ignition timing, checked valve lash, changed the oil, checked for vacuum leaks and I'm still failing emissions.

[California98Civic]

Man, that suck a lot. Just spitballing: the catalytic converter?

[nwrubicon]

forgot a couple things,

would the o2 sensor test bad if its not throwing a code? I've read that they don't always throw a code when they go bad but I'm experiencing such horrible fuel mileage one would think that its running so rich that the o2 sensor would fowl and throw a code.

also, I did a quick cleaning of my egr valve and ports using carb cleaner and when I took the valve off the exhaust side, or the round hole, was dry black carbon as one would expect to see, however the intake side, or the rectangular hole, appeared to be wet, almost black oily looking. The "oil" substance had no smell too it and it was pitch black. Is this normal?

and finally, I was told by a master mech. at my work that the cat should be colder on the inlet side than the exhaust side. I find this to be true due to continued combustion in the cat however, this wouldn't solve my issue. theoretically a fuel injected engine shouldn't need a cat to completely burn all fuel.

[slownugly]

ive seen bad o2s cause driveablility issues on these engines without an engine light but it only knocked mileage down 3-5 mpg. even if you unplug the sensor and run in limp mode they still get high 30s low 40s.

what about fuel injector spray pattern or leak down after sitting?could someone have replaced the injectors with larger ones? the cx and vx came with 190cc injectors i believe. dx,ex,lx,si came with 220cc. maybe a previous owner had them replaced and didnt know they were different?

[nwrubicon]

Injectors could be the issue, I feel like they've at least been taken out as one of them is rotated like 45 degrees so someone has messed with them, I was told to do a leak down test on them but I'm not sure how to being that there's no scherader valve on these fuel rails are there? This weekend I plan on pulling them and checking/cleaning them and if need be I'll take them to dr injector and have them flow tested and cleaned there

[slownugly]

To do it by fuel pressure a sophisticated fuel pressure tester will have the adapters for Hondas. It attaches to the fuel filter. You could remove the fuel rail and crank the engine with the injectors squirting into little jars or bottles and watch the pattern. And turn the key on and see if any drip without cranking.


Edit: also check to see if any part numbers are on the injectors and run them

[user removed]

Just put a gauge on them (injectors) and see if they hold pressure.

I've seen bad 02 sensors drop mileage by 25%.

Your VX should putt along at 30 MPH in 5th at 1000 RPM smoothly.

A flow test of the injectors, comparing the volume of fuel would be a good idea. It's very possible that someone replaced one with the wrong replacement, especially if you see evidence of tampering.

regards
Mech

[nwrubicon]

alright so I tested the o2 sensor today and to my disappointment it is still functioning as it should. It reads .24v at idle, when in lean burn at a steady cruise I was getting around .88v and when not in lean burn i.e. flooring it I was getting -.78 or so. other times I would get higher and lower numbers but those seemed to be pretty consistent.

We also tried to check the cat to see if it was bad or clogged using an infrared thermometer to look for higher temps on the output side of the cat however this was impossible due to the stupid heat shielding around the cat and exhaust and the few small spots in which I could read around the heat shielding I wasn't able to get a reading because the temp sensor doesn't read that high.


One thing to mention is that we checked the resistance of one of my spark plug wires and found that it only read .25k ohms and then we tested a much much newer ngk wire that I had sitting on the shelf and it measure 18.4k ohms....is this anything to be concerned about?

and I want to reiterate that it runs flawlessly. I daily this car around 16 miles each way and it doesn't even so much as hiccup. the shift light comes on as it should, I feel when I'm in leanburn and when I'm not. it just smells rich, wont pass emissions and I'm getting horrible mileage. should I suspect the ecu?

[user removed]

What does the temp gauge read when it is warm, possible thermostat? OEM stats fail open so the car will run too cold which could mean fuel enrichment. Should be just below halfway on the gauge when warm and should warm up within two miles. I don't see wires as the problem.

regards
Mech

[nwrubicon]

I'll take a pic of where it gets too, its just below half way on the gauge and it warms up quicker than any car I've owned. and I replaced the thermostat a couple weeks ago and I've yet to have it actually open yet as the PO removed the coolant valve going into the firewall and bypassed it with a piece of pipe so I always have heat.