alright so I have 91 Honda civic hatchback I haven't looked at the engine code on the engine so im not exactly sure what engine it is and im new to the civic. but I want to get this thing up and running at full capacity. I bought this car from a guy around a month ago and this is what ive done. and plan to do.
My GOAL: is to just maximize the gas mileage because I know this cars can get in the 30-40s.

the car has 240k on it
New radiator
new front wheel bearings and tie rods (they were bad)
new clutch.
looks like it has new wires.
all lights work, heat works, ac doesn't but it blows still.
new tires.

Im thinkin of doing:
NGK Plugs
K&N air filter
new fuel filter
new o2 sensor
Tokico coil over springs
Maybe a MAP sensor.

ok here is the problem Im only getting 15 MPG!!
the CEL was on so I printed the sheet off and checked the LED for the codes.
I got 5 quick blinks then 16 quick blinks.... so code 5 & 16 correct?
ive read on another HT forum explanations of how to fix these codes.
Code 5 says could be MAP sensor hose, but if its the voltage its a bad motor.
Code 16 says Main Relay, or Bad Injectors.
this being said is this what is causing my HORRIBLE gas mileage? I mean I get better than 15mpg in a sports car! im in it to win it with the civic tho and my ideas are to one get answers from these forum on what parts I can buy and replace that may be bad on the engine. orrr try to find a New engine and do a engine swap. I was blown away by all the knowledge on here any and every bit of help or any kind of answer would be thankful!

 

I would replace the MAP sensor with someone's who you know works or a new one, reset ECU and see if your still getting both codes, code 16 from what I hae read really only applies to 88-89 and that in 90-91 it can be a lot of things like fuel filter, fuel regulator, possible clogged cat.

But I do know that I had code 6 for MAP and I replaced mine and it was fine after that, also you could throw code 6 if one of your lines to it has a leak.

 

ok this is what im doin this week MAP, 02, fuel filter, air filter, PCV valve, TPS and maybe a tuneup. hopefully this will fix the code and my horrible gas mileage.

On another note commented on another thread with a guy who had a 91 hatch with all the same problems and said he could never figure out what it was/ replaced everything I am plus the CATs. so im a little doubtful now but we'll see. im in the army and going out to the field for 3 weeks so it may be a while before I can put the parts on and run a tank of gas thru to see whats goin on. but I will be back on here to post my progress and results.
and thank you for your reply lopa!!

 

hey guys I was just throwing out there that ive now replaced the fuel filter, pcv valve& hose, o2 sensor, valve cover gaskets, tuneup (plugs,wires,cap), MAP sensor. I plan to put a tps this week and see how much all this helps. I just filled up and ive only gone 11 miles so I cant really see if all these parts have helped with my horrible 15mpg I was getting. I was throwing codes 5 & 16. that's MAP sensor & injectors.

well after putting all the new parts on I reset the ecu and now code 16 has gone away soooo im guessin the fuel filter was just sending bad fuel to the injectors & throwing the 16 code. Sadly even after replacing the map sensor code 5 is still showing... ive checked hose #21 its good with no cracks or tears, so for code 5 the only thing left to replace would be the throttle body or ecu itself. correct??

I will say the car does seem to run a little smoother now, but when I crank it she still sends out some white smoke for a minute and the smell of raw gas is still very apparent. what else should I look for ? ive seen rusty gas lines so that's goin to be next along with the new tps. ANY help would be great!

Lastly when I pulled the valve cover & replaced the gaksets, I noticed the white milky moisture substance in the valve cover and on top of the motor. the car sat for a month so I believe its just moisture, am I right ?

 

I also replaced the air filter with K&N filter. and the engine is d15b2, I don't know what the heads are. is there any where to look to figure this out or do I have to take the engine apart.

 

 

thanks Honda parts hero I printed that trouble shooting diagram out. looks like I need to buy a vacuum gun or just replace the throttle body or ecu. because the #21 hose is good and I have replaced the MAP sensor.
any other advice on my other questions would be great!!

 

Just curious, what color are the wires gong to your map sensor now?

 

I don't know I can find out tomorrow when I get off work and post it on here.
what color should they be? so I will know what im looking for.

 

bump for answers, any help would be greatly appreciated!

 

How did the troubleshooting that HondaPartsHero posted work for you?

 

Keep throwing money at it!!
We'll keep spitballing ideas at you, and you run out and get parts and throw them on there! See if that works!!
Gotta save money on gas!!!

 

hahaha your right baller status. ive put about 500-600$ in parts as of now. but hey if it gets the mpg up to 25-35 area I would happy and fine with that. soooo KEEP throwin ideas and ill keep throwin the money$$$$$


as far as the troubleshootin goes I just got the vacuum gun I ordered online in yesterday so Monday I will get on the rest of trouble shooting to figure out code 5. although I believe its the throttle body or tps or ECU

 

Also, do a proper map sensor wiring check.

 

ok is there any diagram that I could google to make sure it is wired correctly.