VX Tune Up & Suggestions for 50mpg
 

I'm happy to say that I am a proud owner of a 94 civic vx, whereas at this time, I am preparing to give the car its first complete tune up since I bought it this past October. I've no idea what the last owner has done to it, so I would like to be through. There's over 235,000 miles on the vehicle; but in spite of that, the car runs fairly well with some minor issues.

The first issue is that the idle appears to fluctuate at a dead stop, or while driving once the car is warm. At this point the needle appears to flutter between 1000 to 2000 rpm.

The second issue is that the car seems to accelerate poorly on the freeway or while driving up hills. Is this normal? I often find myself with the pedal down to the floor, as it slowly speeds up to 55mph or struggles to maintain that speed while going up hills. In fact, passing another car is simply out of the question.

The final issue is that the fuel economy is averaging around 35mpg. I couldn't even tell you what lean burn mode feels like.

Aside from all of that, there are no trouble codes or other issues to be found. So with everything in mind, I'm wondering what else should be included in my tune up.

So far, I've purchased OEM parts from Majestic Honda to include the following: Spark plugs (ZFR4F-11) , distributor cap, rotor, PCV, fuel filter, air filter, 5 wire O2 sensor (L1H1) and the screen for the fuel pump.
I've also read postings that suggest cleaning out the IACV & the EGR valve.

Finally, would it be excessive to replace the MAP sensor, fuel pump, and ignition coil, or fuel injectors? Thank you.

Do you mean you installed the new parts and there was no change at all ?

Did unplugging the new OEM o2 sensor make any difference ? As Ryland suggested in your other thread.

When you say fluttering idle do you mean hunting up and down or do you mean missing as in a non firing cylinder?

The vx hardly ever activates egr so I would not spend much time on it until you get the rest sorted out. Just make sure it is not stuck in the open position. Stuck closed is ok at this point

Like most cars the vx has quite range in mpg. Summer vs winter.long trips vs short trips. 35 mpg in the winter. Yep I have got that before. See my fuel log if you want

No parts have been installed as of yet including the new OEM O2 sensor, given that's it been -20 degrees below zero in my part of the country. By fluttering, what I'd meant to say was that the idle was"hunting up and down". I'm happy to say that I don't appear to have a missing cylinder.

Oh ! In that case I would install the tuneup parts only and go for a drive before you change out the o2. It is possible you already have a good o2 and you can keep one as a spare. Troubleshooting is always best done one change at a time and may help someone else here on the forum. Good luck!

I had all the problems you had, and replaced a lot of what you did with no difference.
But when I tested my fuel pressure and found it was below specs, i changed the filter and the pump and it ran like a NEW VX!!

Lean burn is like what you described, over 55mph the car feels like it's dragging a parachute. Your foot control dictates mileage more than anything