jimmy o.

ok ive looked at everything the only possiblities left (in my mind anyway) a bad o2 (its not throwin a code tho) and a plugged cat my car is shootin out a lot of black $hit (unburned fuel) not throwin any codes idk if one of the above could cause my mpg to be this bad (21mpg) and dont post tune up it is all brand new exept mentioned unless you think ive forgtten somethin... thanks

also my exhaust feels like it is resricted thats why i look at the cat...

z6htch

Hey man mine is just as bad! But I have low comp pistons b/c I'm doing a turbo build. Should mine be that low b/c of them?

jimmy o.

mine is stock rebuilt with maybe 2k miles on it
you probably need to chip your ecu for running low comp pistons on the na until you turbo it

jimmy o.

come on ideas anyone

green99civic

are u getting any codes could be maybe your 02 sensors arent working proberly and causing your motor too run rich all the time...

Is your exhaust smell like Gas? is your exhaust pipe black?

Jimster480

ya it oculd be a cat problem. Or a bad O2 sensor that doesnt throw a code. They dont always throw codes...

jimmy o.

no codes alot of balck $hit on the bumper and in my exhaust tip which is unburned fuel

95exstocker

my buddy had the same problem and was getting about the same mileage...its was his IAT that was faulty....its a little guy on the back side of the intake....its held on by like one screw...may want to check it out?

bossm

first thing is check your compression on each cylinder if it is shooting black smoke could be your head gasket

jimmy o.

i dunno my car idles fine sometimes its want to idle pretty low around 500rpms after its warmed up but most of the time its idles normally a little rough though

bossm

DO A COMPRESSION TEST ASAP thats the first thing to do

jimmy o.

uh i have a new engine in my car my car would have absolutely no power if it had a blown headgasket and would smoke constantly not to mention overheat which it dosent
-blue somke=oil
-white/grayish=coolant
-black=unburned fuel

Former User

-As already mentioned, you might have a lazy O2 sensor.

-There may be a leak in the exhaust manifold near the O2 sensor. Such a leak would raise O2 levels around the sensor, improperly causing the ECU to compensate by increasing fuel to the cylinders.

-The fuel pressure regulator may be stuck closed or a fuel injector may be leaking.

REDesignIT

this is pretty normal for a hot motor, my car ran the same kind of numbers 18/19mpg, lots of crapbon build up on the bumper etc. But put down sweet times for the limited amount of work done on it. No codes, 94 ex coupe, headers, intake full exhaust etc.

If you always drive it hard then its mapped for more constant fuel increase in air velocity etc, to solve you need a new ecu map and some tunning such as Hondata chipped ecu etc. You can probably get another 2 tenths in the 1/4 out of it, but really its going to lean it out on the top end so if you spend a lot of time in the top end of the rpm band banging the gears or winding it out (on stock gears my car would hit 93mph in third with 205/45/16's) and about 6,900- 7,000 on stock internals...

Opps I forgot to ask how does it drive ? fine, accelerate hard all the way to redline ? dog off the line ? fall flat after about 5,900 ????

bossm

sorry didnt read through your post

Tate in action

(on stock gears my car would hit 93mph in third with 205/45/16's)

um i dont think this has alot to do with his mpg.

***

REDesignIT

umm yeah it does, since my D16Z6 had the same kind of MPG with mods and thrashing the car to redline in every gear.

If the motor is all stock and he drives like a grandma than its probably something more serious....

He has a rebuild with a .020 (same as my motor after I burned 2 rod bearings at 194k) headers, exhaust, intake (same) I had a 40mm? JG TB and match ported intake. So the mods are pretty similar. He is rolling on SI wheels diameter wise should be pretty close to the 16" wheels and profile I had.

So if his car can hit 93 in third before redline, then aside from running a little rich its not a major concern. If he wants to clear up some of the exhaust "debris" and gain a few mpg then he needs some ecu tunning. Simple.

So you can relax on the noob comment.

Jimster480

are you getting 21mpg city or highway?

DTA-Zombie

I'm gonna say his driving - gonna guess he hasn't reset his ecu or anything...

if you have the car in neutral and rev the motor does it rev freely? do you get a puff of smoke or anything like 3-5 seconds after letting off? do you accelerate just fine? What ecu? what are the conditions constant stop and go? do you "race stop light to stop light"?

there are a lot of factors...and I love the details on what all you replaced...

REDesignIT

Zombie OP has a build thread for the coupe, white nice DD or toy, whale ***** intake, header that looks like ceramic DC's I think he said skunk 2 exhaust, regarding engine mods and a fresh .020 overbore rebuild. Fuel mods not mentioned nor spark, looked stock from the pictures.

With a setup like that I would imagine stop light to light, lots of holding it in gear just to wind it out etc. Mine was lucky to hit 16/17 city pulling antics like this and 19 on the highway, again full redline shifts and lots of time in 5k 6k rpm even on the highway, 4th is so much more fun at 70 75 around 4,800 to 5,000 rpm with a pretty much open exhaust and a flowmaster single chamber..... great times

EG_Warped

g/l with the resolve dude

Tate in action

but seriously what does how long your third gear has to do with it. so relax

green99civic

sounds like to me man if your not shooting out any codes and black smoke and all that garbage around your tail pipe you prob. have an bad cat. u know for sure if u have a bad cat if you can smell the fuel.

jimmy o.

ok the last tank i ran though i got 291 miles for 9.6 gallons used about 30 not too bad but considering all of it was highway its not too great
im about to order a resinated test pipe as my cat is garbadge (190k on it, it came off my other EJ) the header leak i already fixed i will try and play with it some more