[94civiclx4dr]

Hi guys,

After reading the sticky on gas mileage, I've started to replace a few things that could be the culprit to my terrible gas mileage.

Let me start with the specs of my car.

Its a d15b block, d15b7 head, si headgasket (8.55:1 compression)
Automatic transmission
Oem everything.
Tires @ 40psi
No tuning modifications at all.
New NGK Spark Plugs and Wires

Before I was getting an average of 22mpg. I just changed the fuel filter with an autozone replacement and now only got 190 miles out of the next tank of gas!! I verified there's no leaks after the replacement.

I pulled the o2 bung in the cat (obd2 cat on obd1 car, so bung closing the second O2 sensor hole) and it was BLACK as was the exhaust tip.

This leads me to a bad O2 sensor which I am going to change tonight.
I honestly have no clue how to check timing at the distributor, or valve lash so I'll be looking those up shortly after I finish this post. I highly believe it could be the distributor as I noticed recently it was only being held in with 1 bolt. I've since fixed that, so no more oil leaks at least.

From there if anyone has some ideas as to what could be causing such a major drop in economy I'll appreciate the support. I'll also be checking compression and would love to do a leak down test, but I say that term to all the tool rental places around here and they look at me as if I have 3 heads.

Thanks again in advance.

James

P.S. I have an intermitent sputter while the car is warming up, I would go as far as to say it sound like a misfire. NO cel lights

P.P.S I definitely think I have at least a distributor timing issue after reading a thread on how to set it.

 

[94civiclx4dr]

Could be an exhaust leak.

Excuse my ignorance, but how would an exhaust leak be responsible for a 10mpg+ drop in economy? Unless it was an exhaust valve leaking?

James

 

[94civiclx4dr]

here are some things that have helped me increase gas mileage.

new plugs (check), cap, rotor, spark plug wires(check), fuel filter(check),
change o2 sensor doing tonight
change coolant temp sensor
valve adjustment
double check your timing doing tonight
maybe run some injector cleaner or fuel system cleaner through the car doing tonight

also is the car aligned correctly? improper alignment can lead to poor gas mileage.

Thanks for the advice

 

[94civiclx4dr]

exhaust leak infront of the o2 sensor causing a lean reading maybe.

Oooh otay... the o2 sensor is in the header though so that would have to be a leak between the block and the header.

 

[94civiclx4dr]

I'd check the studs around the block. Just make sure they're tight. Sometimes the noise will vib. them off.

Most likely as far as leaks go, I would check by where the header meets the piping. Sometimes air will make it back up in there causing the O2 to think the car is running lean and it'll dump more fuel in there.

That reminds me, I need to pick up some spring bolts for my car tomorrow. I can hear air sifting out the collector. I just used some random bolts and I know they've come loose cause it didn't do it at first. :yes: It'll increase my gas mileage a bit.

If your distributor is held on by ONE bolt, you definitely need to bust out a timing gun and check your timing... and definitely get the other 2 bolts....

Thanks for the advice. I've already put the other two bolts in but no guarantee that timing is right.

All my gaskets in the exhaust system are new and have the oem style spring bolts.

I dont drive like a loonatic but even if i did, 19mpg from a stock d-series? :dots:

 

[94civiclx4dr]

How do you drive or what is your driving style like?

Are you constantly trying to go around people, do you drive with the flow of traffic, or are people constantly trying to go around you??

Have you tried connecting up a vacuum gauge, driving around with the gauge in the car to see if you are getting normal readings? Or just hook the gauge up, start the car and pay attention as to how much vacuum you are pulling at idle, at 2k rpms... Best way is for the engine to be under load when trying to diagnose with a vacuum gauge.

BTW, driving with a vacuum gauge can very much benefit you in trying to get good mpg. I just connected one in my car about 2 weeks ago, and so far on this tank I have 177miles and I'm only at 3/4 tank to go... Driving style will affect gas mileage probably more than anything will.

I'll have to do some more searching as I wouldn't even know what numbers I should be looking for.

Thanks

J

 

[94civiclx4dr]

I'll help you find a link... the vacuum gauge is really only going to tell you how healthy the engine is....

Here's the one for MAP sensors: Manifold Absolute Pressure MAP Sensors

Vacuum gauge for engine diagnostics: Browser Warning

Thanks for all the suggestions everyone.

I'm going to start with checking the timing once I can get my hands on a timing light, then go from there.

Thanks again

I'll be sure to report back

James

 

[94civiclx4dr]

will check the above thanks guys.
Unfortunately I didn't get a chance to change the o2 as the other one i had was a 1 wire, thought it was a 4 wire... oh well.
Put in some sea foam. Couldn't check timing since I don't have a light and neither autozone nor advance rent them (WTF!?) I don't really want to pay $50 for a light I'm going to use once.

I did advance the distributor timing by rotating it a hare towards the firewall and it seems to have stopped the intermittent sputter i was getting before... ugh i dunno quest to find a light now.

 

[94civiclx4dr]

Dizzy problems makes sense. I wish I had checked my timing before mine took a crap.

You need more than one bolt in that thing man. Please get that fixed.

It has 3 bolts now; fixed that the same day I noticed it.
I did notice yesterday I still had oil on the front of the motor and was over a quart low. Looked like it was still coming from under the distributor area. :uh:

Bone, I'll double check cam timing. Anything specifically you would recommend I pay close attention to?
I'll be doing a compression check again tonight just to double check. I didn't smell any fuel in the oil or exhaust though.

 

[94civiclx4dr]

I noticed smoke in the rear view mirror yesterday when I was getting on it on the parkway.... fml

It was grey/light blue ish any ideas

 

[94civiclx4dr]

Doesn't sound good whatever it is. A seal or gasket maybe?

well white or blue has to be oil or coolant right?
I'm losing oil i know but i thought that was from my distributor only being held in with one bolt before... Turns out that may not be the case / thats not fixed yet... ugh

So my thoughts are : Valve seal maybe Piston rings

 

[94civiclx4dr]

Ok so now I'm down to getting around 18mpg.. I'm at 160miles and on EMPTY (not quite prolly anothe 20 miles in 'er)

There's something obviously wrong. Just waiting til friday to get my leak down tester due to the smoke i noticed the other day.
I hope it a valve seal since i need to get a p-08 head anyway

 

[94civiclx4dr]

valve seal won't effect gas mileage.

nor will shitty leakdown numbers.

110-120 psi cranking, 25% leakdown or more on all cylinders, still getting 32-34 mpgmixed city/highway.

:wacko: I'm seriously lost then!

I just did a quick compression test since I have the tool and it came back good cylinders 1-4 were 180, 180, 175,175 respectively
I lose oil at a rate of about a quart every 800 miles and am getting 18mpg

Does anyone think maybe my rings are still bad, if not just the oil rings? I was reading this thread; seemed he had a similar problem
http://www.honda-tech.com/showthread.php?t=2228601

Any suggestions on steps of things I should check would be immensely helpful and appreciated.

James

 

[94civiclx4dr]

ok just bought a light and checked timing; I think i'm way off
My marks are at least a half inch towards the firewall than the pointer even when i adjust the distributor all the way. Going to check cam timing now

 

[94civiclx4dr]

Check mechanical timing, how everything lines up when off. Also you need to jump the service connector to make any true changes to ignition timing.

Doing that now, Also noticed i have code 43 relating to the o2 sensor... PROGRESS at least..

 

[94civiclx4dr]

Can you explain... what do you mean by jump the service connector?

This would be an excellent DIY... how to check Cam and Ignition timing... I really need to check my ignition timing as well.

how to find mechanical TDC
How do you find TDC on a Honda Civic D15B7 with the crankshaft pulley attached? - Honda Car Forum - Accord Parts Civic Tuning Acura Racing

how to set distributor timing

http://www.hondacivicforum.com/forum/showthread.php?t=16210


no offense but i found these with a simple google search in less than a minute

 

[94civiclx4dr]

**update**

Bone, you called it; I was off on both mechanical and distributor timing.
I also have code 43 which correlates to the O2 sensor, so i'll be buying a new one tomorrow, then to fill up the tank and see how far I get.

Still have to figure out this blue/white smoke on acceleration :sigh:

Hopefully i have one problem sorted though. Thanks everyone!

 

[94civiclx4dr]

Just a thought Im throwing out there; could the fact I'm burning ... something be affecting my O2 sensor, causing the cel code 43?

P.S. this is what my spark plugs look like

 

[94civiclx4dr]

that plug is rich, very rich.

Time the car, then see what happens.

Like bone says.

Also, a lot to rich can soot up an O2 sensor and stop it working. They can be cleaned with heat from a slightly lean butane or oxy acetylene flame carefully applied to the correct area.

Thats what I thought! As you called I was off on both distributor and mechanical timing.
1 tooth off on mechanical timing (the 3 marks were about 1" to the right of the indicator)

I've fixed that and installed a new bosch oem style O2 sensor already.

While I may be running rich, do you think that the condition of the plugs could be somewhat caused by the same issue causing my blue/white smoke?

If timing doesn't fix the rich condition, what would be the next suggestion to look at? Vacuum leaks? MAP sensor? PCV Valve?

Could a stuck open PCV Valve be causing me to burn oil ?

 

[94civiclx4dr]

Oil burning leaves shiny black smooth deposits on the plug, like a coat of paint. Excess fuel leaves flat dull black deposits on the plug like it was dusted down with powder.

As it ran with the cam timing out one tooth, you may have bent valves.

Cam timing being that far out will kill VE and compression. That will impact on fuel metering and combustion efficiency.

Ignition timing being that far out will kill combustion efficiency.

Try it with the timing fixed. Once the soot burns off everything, it might be OK

It may not have been a full tooth but it was definitely off.
It's looking better already mileage wise, 35 miles and the needle hasn't moved yet before it was at least an 1/8 down.