B serious

iTrader: (1)

People's definition of city vs. highway is disputed vehemently. Suburban driving is a mix of city STYLE and highway STYLE driving. Your commute at a 30mph average doesn't take you anywhere near a traffic jam....just like it doesn't take you anywhere near a highway.

City and highway are types of driving conditions. Not related to geography. A person driving through Chicago at 1AM on a weekday will get better MPG than someone driving through the middle of nowhere and hitting a freak traffic jam.

A good way to equate this is your average MPH. EPA estimates won't consider a 30mph drive to be "city" miles.

Your MPG is lower than one would expect. But expectations and results will vary for each individual factor. You can still average 30mph and get "city" gas mileage. But its not common...and will likely have more to do with driving habits or environmental factors that are unique.

Your P0420 may be some sort of indicator also.

Maybe your catalyst failed because of some crazy stuff they put in Canadian fuels? Or maybe the car is habitually running rich due to a failed component and is killing the cat.

Or the cat is broken apart and is blocking exhaust flow.

RT_NEWYORK

I have an em1. Currently the cat and o2 sensors are busted with cels. Car hasn't had a tune up in years and I routinely get about 330-340 to a full tank, I drive with a heavy foot and put the car in vtec often. Just putting in my 2cents for more comparisons from the same car and engine.

B serious

iTrader: (1)

Also worth axing....how long does it take for your car to come up to operating temp?

CRXyes

do a goddamned tune up.

frost6

Your P0420 may be some sort of indicator also.

Maybe your catalyst failed because of some crazy stuff they put in Canadian fuels? Or maybe the car is habitually running rich due to a failed component and is killing the cat.

This is what I want to know, what components would cause the engine to run rich? I do not want to be out a cat if there's an underlying problem that's causing it.

As far as gas is concerned were getting the same fuel that you guys south of us are getting (probably higher quality because ***** hella more expensive)

B serious

iTrader: (1)

EM1's had an issue with the ECU being too sensitive and setting a CEL for catalyst efficiency. Mine would turn off if I drove the car at 100mph+ for long periods of time. Then would turn back on later.

If it is actually running rich....your FPR diaphragm could be torn. Leaky injector maybe. I had another EM1 that had a clogged MAP port so it always read low vacuum. Could be a lazy TPS.

What spark plugs are you using? What did your old plugs look like?

B serious

iTrader: (1)

Still axing

frost6

Old plugs were in good shape, one of them seemed to be caked on (probably over tightened) but did have some white substance near the bottom of the threads, but the sparky looked clean and good otherwise. Replaced them with ngk iridiums.

Haven't timed the warm up times but 2-3 minutes usually is when the temperature begins climbing up.

B serious

iTrader: (1)

Hmm. Plugs weren't covered in black soot? That kind of indicates that it probably isn't running too rich.

Could your catalyst be broken? Heard any rattles?

frost6

No, but also I'd like to add that the previous owner had the car just sitting for a while, there was minor black sludge comming from the exhaust on first start and I have no records of the vehicle from him other than the car is an original. Car did look mechanically sound when I bought it and drove excellent and still does drive strong, just the curiosity of the mpg from it.

There weren't any obvious signs of a bad sparkplug other then white residue on one of the sparkplugs.

The cat at idle I don't hear anything wrong or out of the ordinary, but I know for sure something is wrong because even after CEL resets, if I ever go on the highway it comes back on, happened at least 3 times.

frost6

Just did another fuel up, ran 404 KM's (251 miles) with a fill up of 36.36L (9.6 Gal), seems like its improving on its own?

tony_2018

Its probably because you are more aware of the fuel consumption and you're compensating.

frost6

Actually I've accounted for that, I tried not changing my habits, maintaining consistent driving behaviours that I outline before (3500 rpm shifts, no harsh acceleration etc), nothings changed in my driving habit or route aside from the increased mileage, but I'll keep an eye out on the next few fill ups to get the average.

B serious

iTrader: (1)

Try different things to see if the mileage improves or worsens further. You're too worried about setting a habit at this point. Just shift whenever it feels good to shift. I don't observe too much...but unless I'm driving my TSX or ITR with their big elephant sized engines...I don't think I ever shift at 3500RPM when accelrating. I found better MPG by just shifting by feel for each situation rather than setting a specific shift point.

B serious

iTrader: (1)

~26mpg for a 30 mile round trip commute at a 30mph average is pretty much the most normal **** that's ever been recorded, though. You're in the majority region.

But hey...keep altering your driving habits. Maybe you can improve it, if you are so inclined.

tony_2018

Especially no cruise control. if you use cruise control it will constantly try to adjust the throttle to maintain speed.

kingkau

Check the Air filter

frost6

Well yeah, sorry if it's not clear but I don't shift on straight up 3500 but I do get a feel for the shift and generally it's always around 3500 give or take a few hundred rpms due to hills and traffic which is why I set that as my base.

frost6

Cruise control has been removed from the car.

B serious

iTrader: (1)

But...its so convenient for yourself and everyone around you. :'(

frost6

My routes don't justify cruise control lol to many damn lights and speed reductions.

purgat0ry

iTrader: (3)

I'm at a loss why anybody'd remove cruise control :/

frost6

Previous owner :/ just never felt like i needed to put it back.

B serious

iTrader: (1)

I don't use it unless I'm out on the an open highway or coming home late AF to/from the burbs. I've held off on getting an aftermarket steering wheel because I love my CC...and am too lazy to re-locate the buttons.

frost6

yeah thats the problem, there ain't no open highway where I live unless I'm south of the border which is very seldom, only a **** ton of choke points scattered all across the metro area