Syndacate

EDIT:
Forgot to include:
'95 EX Coupe 109k, stock Z6 motor.
Mods: None, just I/H/E, and if you want to count that stupid B&M adjustable fuel cap - go ahead, but the engine's stock.
/EDIT

I used to get 36mpg on the highway at 77mph w/ cruise control on going from my house to Rochester.

Then it dropped off to 26mpg on the highway...an abnormality - maybe the traffic was harsher or something. Then when I left for the summer I pulled a 24mpg - which I attributed to the fact that my car was 2" lower due to all the luggage I had in there (which shouldn't have lowered it that much).

Now on one of my trips back here I got ~24mpg w/ the same 75-77mph cruise control on the highway and then when I got home - around town, lots of back roads, lots of shifting, lots of hills, I got 2<u>6</u> mpg! <u>The most important special circumstance here - is I'm getting 21-26mpg BOTH ON and OFF the highway!</u>

Last night I clocked it - mix of highway but mostly town and got 21mpg. Now keep in mind I was having fuel issues and throwing code 43 (fuel supply system) but I think it's fixed after a fight w/ the company after they gave me the wrong regulator, etc. etc. - fixed it w/ an adjustable cap for the regulator from B&M - adjusted it to 45 psi - haven't gotten the CEL yet, but whatever.

So up to that point I had fuel issues, obviously I'm gonna continue to clock my mpg and see if it normals out, in my area most pple w/ 4 cylinder engines (neons 'n such) get 23-27mpg around town and maybe 29-31 highway.

What I've changed:
- Fuel filter in engine bay (before fuel rail).
- Fuel filter in gas tank (attached to fuel pump)
- Checked power on all 4 injector plugs with a test light and am getting power from each plug on the positive terminal
- Readjusted the fuel pressure to ~45psi (helms calls for 43-47~).

I haven't changed my fuel pump yet b/c with my exp with electronic fuel pumps they go until they die, there's usually not a "dying period." It's usually very binary, they're going, then they die.

The car seems to be shaking a little ~2-3k RPM and in my experience with Hondas that usually means wires are going. I use Bosch wires and never had a problem with them although a lot of people recommend NGK wires, and I use NGK V-Power plugs.

The plugs are black now b/c the stupid FPR they gave me before ran it at 75psi - but they're not fouled, it should blow it off soon, but whatever, I got another set. I'm going to change wires, plugs, rotor, and cap in the near future, hopefully that will help.

I always use NGK V-Power plugs - but as far as wires go, I've always used Bosch - never had a problem, but for some reason H-T pushes NGK wires like they're cocaine. Can anybody verify that NGK wires are better or is it some group logic thing and it really doesn't matter?

21mpg hw in a civic is pathetic, I got 15 highway with my '67 Z28 after I installed the overdrive gear and that had a 429 bored out to a 509 in it...so I mean ****, if I'ma get 21mpg on the highway, I'm better off w/ a V8 at this point, jeez .

Another possibility can be a clogged injector or one that's stuck in the "open" position. Is there anyway to check this? I don't feel like buying a new set as they're $96 (was the cheapest I could find and that was from http://www.hondapartsdeals.com.

Another well brained friend of mine (very smart when it comes to cars) said it's possible that it's the O2 sensor - which it most definitely is, but for some reason I don't think the O2 sensor is going to throw off the fuel mileage down that much.

I mean I really don't figure there's that many more parts, I mean if you break it down basically, fuel pump, fuel filters, it's not leaking anywhere, fuel rail, injectors, and fuel pressure regulator - it's not a very complex system .

I greatly apologize for the length of this post as it's very long and very unorganized. Though if you read this is probably means you read the whole post - so thank you for reading, and any help is greatly appreciated. TIA.

t0p_sh0tta

You're a long winded one... Can we have the abbreviated version?

Are you saying that you have a B&M FPR? Replace O2 if it hasn't been done, and cap, rotor, wires, air filter, fluid change, tire pressure, etc. Basic tuneup stuff.

uneek360

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by t0p_sh0tta &raquo;</TD></TR><TR><TD CLASS="quote">You're a long winded one... Can we have the abbreviated version?

Are you saying that you have a B&M FPR? Replace O2 if it hasn't been done, and cap, rotor, wires, air filter, fluid change, tire pressure, etc. Basic tuneup stuff. </TD></TR></TABLE>

lol... the short version

elmo908

0xygen sensors tell your engine how to run so perhaps this could be true. I just pulled a O2 sensor code today and purchased a nippondenso oem unit for $130 with tax.

instructor74

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by elmo908 &raquo;</TD></TR><TR><TD CLASS="quote">0xygen sensors tell your engine how to run so perhaps this could be true. I just pulled a O2 sensor code today and purchased a nippondenso oem unit for $130 with tax.</TD></TR></TABLE>
++2 I have replaced two O2 sensors on my d16z6 in 215k and in both cases the mileage dropped even lower and only the first one gave a cell the second one I caught as the mileage started to fall off and was in the car for 90k by the way is the same amount of mileage I got out of the first one.

00Red_SiR

I'm just trying to understand all this. So you're saying that your gas mileage started falling, you fixed your FPR and now you're waiting to see if the fuel economy has gotten any better? I can tell you right now that if your FPR was operating at the pressure you said it was, it certainly would have been responsible for the loss in MPG's.

Syndacate

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 00Red_SiR &raquo;</TD></TR><TR><TD CLASS="quote">I'm just trying to understand all this. So you're saying that your gas mileage started falling, you fixed your FPR and now you're waiting to see if the fuel economy has gotten any better? I can tell you right now that if your FPR was operating at the pressure you said it was, it certainly would have been responsible for the loss in MPG's.</TD></TR></TABLE>

True, but would it be responsible for a 10-15mpg drop, is the question. It's doubtful.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by elmo908 &raquo;</TD></TR><TR><TD CLASS="quote">0xygen sensors tell your engine how to run so perhaps this could be true. I just pulled a O2 sensor code today and purchased a nippondenso oem unit for $130 with tax.</TD></TR></TABLE>

Yeah, I'm not getting a CEL, not sure if I'm rdy to spend $ for a new O2 sensor just, quite, yet. I mean ****, I'm looking to swap, boost, or sell the car relatively soon, it's gonna be probably close to 100 for the tuneup (still g2 buy cap, rotor, and wires and the wires alone are like 50 bucks), if I replace the injectors that's $96, and a new O2 sensor is 130 bucks. so I'm looking at ~$300 for stuff that might not even be the problems on an engine that I might not even be keeping that long .

That's not even the money I g2 spend at the pro shop to get the front end rebuilt (which I have to do soon) because when I hit the deer a year ago the guy at the body shop did a half-*** job putting it back together so the part lines are different sizes, headlight doesn't fit right, etc. plus buy another corner light b/c he reused the old one and it looks like ****.

Just trying to weigh if I should keep this thing or not, then let's not forget it's a prime target for thieves.

00Red_SiR

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Syndacate &raquo;</TD></TR><TR><TD CLASS="quote">

True, but would it be responsible for a 10-15mpg drop, is the question. It's doubtful.
</TD></TR></TABLE>

ABSOULTELY! At that pressure, you'd literally be dumping gas into your cylinders and it would have a large effect on fuel economy.

Syndacate

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 00Red_SiR &raquo;</TD></TR><TR><TD CLASS="quote">

ABSOULTELY! At that pressure, you'd literally be dumping gas into your cylinders and it would have a large effect on fuel economy. </TD></TR></TABLE>

Naw, b/c you see, the reason I had to replace the fuel pressure regulator was because it was the original one that came w/ the car and the rubber diaphram on the inside was all hardened and didn't move too well. So I'd be running 39mpg or so until the car reached standard operating temperature in which it would open up all the way and run ~45psi and everything would be peachy - but would throw a CEL from before for insufficient fuel pressure.

So I bought a 2nd one, but when I hooked it up, it ran ~75psi, I took it around the block once, of course my plugs were black as sin, and I disconnected it. It's not like I was driving around w/ it on there.

Then I bought the adjustable B&M hat b/c the speed shop didn't except returns (last time I ever buy from them). Though because it was OEM and not HONDA OEM it didn't have the same size hat so the adjustable B&M didn't fit over it.

So I went to my friend and he found somebody else w/ a Z6 and took their FPR and I put the adjustable B&M top on it and I just set it to ~45psi yesterday, so I think that problem is fixed - only time will tell if I throw another CEL b/c sometimes it would turn on twice a day and other times it would turn on once a month (completely random).

thehatchninja

o2 sensors can make that much of a reason. I'm only getting like 26-28 in my bone stock LX.

Syndacate

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by thehatchninja &raquo;</TD></TR><TR><TD CLASS="quote">o2 sensors can make that much of a reason. I'm only getting like 26-28 in my bone stock LX.</TD></TR></TABLE>

And you're sure it's the o2 sensor?

thehatchninja

haha...my response didn't make that much sense...glad you could understand it.

o2 sensors can make a big difference depending on the type. The one wire O2's don't matter really. But the O2 and the IAT are how the engine determines how much fuel to give. When it's not getting a reading it probably just gives the max fuel for that RPM to be on the safe side.

Syndacate

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by thehatchninja &raquo;</TD></TR><TR><TD CLASS="quote">haha...my response didn't make that much sense...glad you could understand it.

o2 sensors can make a big difference depending on the type. The one wire O2's don't matter really. But the O2 and the IAT are how the engine determines how much fuel to give. When it's not getting a reading it probably just gives the max fuel for that RPM to be on the safe side.</TD></TR></TABLE>

Yeah, I know, for some reason I don't think it's the O2 sensor - but if it comes down to it maybe I'll replace it.

If anybody has any other suggestions or also thinks it's the O2 sensor plz tell - I'd greatly appreciate it.

hall97civic

ok, well just off the top of my head, runing 75 psi of fuel pressure for any period of time when the suggested is 45, could you have damaged your injectors? Also your egr might be plugged up. If you could clean out your ports it really won't hurt anything! Although your intake is different than my d16y5 isn't it.... how is your air filter? also I'd just check your cap and rotor, maybe touch them up with some emery cloth and slap them back in there if you aren't going to keep the car as it is. Then I would check how much resistance (ohms) your plug wires have. No use replacing stuff that isn't broke. Just some random thoughts. Hope you figure it out.
later

spotscivic

get a moped

thehatchninja

why don't you think it's the O2 sensor? Also try setting the idle, then timing. bad ignition timing will kill mileage.

fizeks

just from my experience i had 3 honda's and all 3 of them (with my luck ) all threw code 43... and all its always been the o2. once replaced my mpg has gone back to normal. now im sure that when it throws code 43 im 99.5% sure its the o2.. why dont u borrow 1 of your friends o2 sensors before you buy one and see if your mpg starts getting better, but before you do anything just check out that o2 sensor im definitely leaning towards that being your problem

thehatchninja

o2