ProjectEKnine

Hello everyone I have a puzzling question..

1997 civic coupe, 180k miles on the body and original motor/transmission.

I spun a bearing and decided to do a full stock build.

The d16y7 has brand new internals from Honda (bearings, rings, seals waterpump, oem timing belt, oil pump, oem pistons. New spark plugs, new air filter. The head was fully rebuilt with oem parts and seals, and valve adjustment was done correctly and timing is set correctly. (distributor is in the middle, yes light was used)

Did not change the cap and rotor and wires, in fabulous condition still..

Its been 3000 miles since the rebuild. I have done 8 oil changes so far. Regular dinosaur castrol gtx 5w30 every 375 miles for break in with a magnetic drain plug without going over 3k rpm. I now started to reach to 4k-5krpm and at the 3000mile point I switched over to royal purple 5w30 and filter. Yes I know some may say its a waste of money but honestly $55 for a oil change every 3000k miles from now on is not that expensive and its sort of like protecting your investment, feeding the motor nice quality oil and making it last slightly longer under abusive conditions.

Question is, im getting horrible fuel economy.

I get about 200 miles to 10 gallons of fuel, same driving habits as before, where I would get 350-400 miles to 10 gallons of fuel. Same wheels, same psi, nothing changed expect for a brand new motor.

Is it because the motor is new and still tight and hasn't reallllllly broken in yet? I still have a catalytic converter and the o2 sensors are old but dont trigger cel and ran a o2 sensor test with my Autel MaxiDAS DS708 and it passed. Car has a 2000 SI muffler on it with stock exhaust, and passed NY state inspection in a breeze.

Whats going on here im puzzled?

strategy400

Is it getting up to operating temp?

ProjectEKnine

Yeah, I let it idle up to operating temperature before I drive, usually let the thermostat open two times.

Yes idling = gas using, but I have ALWAYS done this procedure even prior to the motor being rebuilt.

Former User

How OLD are the plugs, wires, cap, and rotor?

What mark on the crank pulley did you use to set the ignition timing? Did you jump the service connector?

Any performance problems?

ProjectEKnine

I'm not sure if I was clear, but I mentioned the plugs are brand new since the first start of the rebuilt motor.

NGK coppers and gapped correctly.

Cap and Rotor are the same prior to the motor being rebuilt (when I was achieveing great mpg, same driving habits, warms up.) And upon inspection there in great condition.

Wires are in fantastic condition.

I know there are a couple colors but I cant remember off the top of my head and don't have the manual in front of me or online but its set to the OEM mark.

Performance is fine, not sluggish, doesn't bog, instant throttle response.

Yes the service connector was jumped during the timing.

Former User

How old are the plug wires? Wires that "look good" can be bad.

You'll find a diagram for setting the ignition timing in the FAQs sticky. Follow the instructions precisely. The ignition timing is set to the red mark (middle in group of three marks).

ElectronBlue00

I'm fairly certain that bad of a change won't be because of faulty plugs or wires. Do you smell gas while your car is running? Even at operating temp? Luckily as you know your engine rebuild most likely is not the cause of your poor MPG. It's most likely electrical, 02 or fuel related.

Edit: since you know your cap/wires/plugs are good. Check the easy stuff. A faulty MAP sensor can lead to poor MPG.

ProjectEKnine

I just stepped out to lunch and can confirm upon checking the timing is set to the red mark.

Also as far as the wires are concerned, these are the same exact wires that were used prior to the motor being rebuilt providing me with great MPG.
There the ngk blue ones, on estimate I say put on about 2000miles before the motor spun a bearing. They have been given 3000miles on the new motor so life wise there roughly 5000miles old.

Also, I am running 87 octane from shell.


I don't smell a trace of gas while the car is running, or when its off. Even sniffing around the fuel filter, any gas line no smells, operating temperature or cold. Its really confusing isnt it? lol

Oil has zero coolant in it, coolant has zero oil in it. Car does not leak a drop of anything after coming home from a drive and parking it on a huge white sheet (i got from the body shop portion of my shop), and no spots of leaks after getting back in the car and moving it the next day. Car also does not smoke, I exhale more smoke with cigarettes then this car HAHA.

Former User

Does the CEL work? Or did you check for CEL codes using a code reader?

Telecatster

+1 and check all ground wire connections are clean and tight (just like I like me women).

ProjectEKnine

CEL works, for example when jumping the service connector it comes on.

Code reader/diagnostic tool I used was my Autel MaxiDAS DS708. Its got cool features like o2 sensor tests where it tells you to snap the throttle and vary it at rpm's to get a proper reading and passed all those tests. It reads zero codes and all categories show a "pass" when I run the diagnostic. I also tried various other readers from my co-workers around the shop, all passed.

I'm looking at the grounds now and there fine, good contact strong connections onto bare metal. Now im pretty good with my mechanics but I don't know everything, how would electronics vary MPG?

Former User

Have you resistance tested the 2-wire ECT sensor below the distributor?

Have you measured the fuel pressure and tested the FPR?

Former User

After the rebuild? If so, did they do an emissions test?

ProjectEKnine

I have not done this yet but will most certainly do so.


As far as emissions is concerned, the NY inspection for obd2 is just a plug in test. But I had a friends garage with the old school dyno obd1 emissions tester and we ran it and the car did fine.

Former User

After the rebuild?

ProjectEKnine

Yes after the rebuild, sorry about that should have specified, I figured it was obvious lol

Former User

Can you post the emissions numbers?

beecee18

Did you check the longterm fueltrims with those scan tools to see if ECU is adding to compensate for a fault/ailing part/incorrect sensor feedback?

The ECU can add a considerable amount of fuel to combat a fault

If the LTFT values are zero'd out then your most likely fine (Just make sure you check after 2-3 drive cycles)
If the LTFT have accumulated a negative or positive value, reset the battery, plug in your scantool, and log the PID's STFT and LTFT (short term and long term trims)
These values should be zero'd out after ECU reset so start it up monitoring the STFT see if these values start to go the same way the LTFT were before ECU reset, drive a cycle or two and if the LTFT start to accumilate again, you will now know that the ECU is responsible for adding the fuel. System too lean code will dump fuel like a mug but you say you have no engine lights.

IMO I really dont see how the ECU could be adding if you blew threw a smog inspection, and everything else checked out good. But this easy fast method is an easy way to squash any ECU related overfueling questions, then the funest part is finding out why....

Make sure your numbers for mileage are correct, and make sure your style of driving is not to agressive as to contribute towards the decreased fuel economy

ProjectEKnine

I'll be honest with you I don't have the print out now, its been a while, otherwise I would have uploaded it.




That sounds nice and techy lol, im going to get some assistance from the master ecu guys at the shop and see what we come up with. This is my daily driver but has become a fun project to conquer. Problems like this are fun, except for burning 10 gallons in 200miles lol.

And yes driving habbits have not changed at all, im very consistent on that.

strategy400

Feel the wheel hubs after a drive to see if they're hot/brakes dragging. Maybe find a slight incline and see if the car rolls freely.

beecee18

No master splinters needed,
just select the live data option and select the two parameters to log STFT and LTFT.
and follow the directions in my first post.

I really dont see much else it can be.

And Im not to sure about using the scan tool for proper O2 response tests.
All makes and models are different so I dont see how a DIY scantool has the ability to give the O2's a proper test.

I dont throw parts at cars but the only problem you have is a decrease in fuel economy on a 16 year old car.

16 year old O2 that has now been introduced to your fresh build.
An airplane mechanic once told me,
"an old man doesnt like change of routine"

So in this circumstance I would throw a new O2 at it.

But thats me

beecee18

Absolutley,
Great suggestion....

Any type of friction or drag, or alignment issues, improper tire pressure, ect.

Mileage ratings/stats advertised from the factory are for new properly broken in units driving in closed loop fueling with minimal driver throttle input.

Taylorej1-93

check your distributor easy clock and bam good running car

beecee18

Right on !?!?

ProjectEKnine

Thanks for the responses again everyone.

Now to answer a couple questions and throw a little information out there about my car.

I have my suspension set up pretty well.

Front is kyb with tein stech springs
Rear is brand new OEM stock height
Skunk2 lca new bushings
New wheel bearings all around
Brand new drum brake kit *everything internally replaced, no drag what so ever.
Front brembo blanks, thermoquiet pads with new calipers and bracket, no drag.

Once car was dropped in the front we did the alignment here, got a good lift for lowered cars. (my boys 5 lug 4 door jdm integra is about 1.3inches off the floor and we did his alignment lol)

I guess the plugs may some how fouled, they look fine. Maybe the 3000miles on them since a fresh motor build treated them bad, all that tight compression and metal shavings I guess.

Now I may just do a full tune up, I get mechanic discount prices ehhh ill just get new everything. I guess the older o2's were "seasoned" with the old motor and the whole "mixture combination" is thrown off.

Ill get new wires, plugs, rotor, cap, o2 sensors.
Tires are 195.60.15 at 35psi, yes there 3% and about a inch taller then OEM, and cause the speedo to drop like 2mph, (i doubt its THAT significant, like I said same as prior to motor being rebuilt)

Now I run ngk copper plugs, any truth to what technically seems correct? Better spark plugs, better spark to atomize every molecule of fuel to produce better mpg's due to the fuel being fully used? If so what plugs do you recommend. I could care less about price.