92 civic vx 29mpg ??help?

[amaterasu71]

Hi everyone, I bought a 93 civic hatch dx for my kids this fall it had 60k original and it has the 4 sp auto. I was so impressed with it as it got 43mpg on the freeway that I kept my eyes open for my dream mpg car the VX model. Just bought this vx here is the stats.. 199,000 miles, new tires, new exhaust, im the 3rd owner, and the car appears to be in great shape as there is just the start of bubbleing of rust spots. the engine light is on and the previous owner told me it was the o2 sensoer, he siad it was really exspensive to replace so he never did. So on my initial trip it only pulled 29 mpg. very dissapointed so im going to change everything oil, filter, air filter and such my question is would the o2 sensor be the cause of such low mpg? what other things should i be looking at? I was hoping for atleast 40 on the open rode i only was driving 55 mph and im really easy on it. looking forward to any help thanks, shawn

[IndyFetch]

Originally Posted by amaterasu71

Hi everyone, I bought a 93 civic hatch dx for my kids this fall it had 60k original and it has the 4 sp auto. I was so impressed with it as it got 43mpg on the freeway that I kept my eyes open for my dream mpg car the VX model. Just bought this vx here is the stats.. 199,000 miles, new tires, new exhaust, im the 3rd owner, and the car appears to be in great shape as there is just the start of bubbleing of rust spots. the engine light is on and the previous owner told me it was the o2 sensoer, he siad it was really exspensive to replace so he never did. So on my initial trip it only pulled 29 mpg. very dissapointed so im going to change everything oil, filter, air filter and such my question is would the o2 sensor be the cause of such low mpg? what other things should i be looking at? I was hoping for atleast 40 on the open rode i only was driving 55 mph and im really easy on it. looking forward to any help thanks, shawn

The O2 sensor is a wideband 5-wire sensor, and is expensive. I know some of the guys on this site have links to cheap ones online. Others have bought them and they work just fine.

A bad O2 sensor in a VX is usually responsible for dropping the mileage from 55-ish to 40-ish. 29 is terrible for that car. What kind of tires are on it? Air them up all the way to the max sidewall pressure. What viscosity oil (run 5W30 or thinner). Check the plugs, wires, cap, and rotor, and replace if necessary. Check for a dragging brake by jacking the car up and attempting to turn the wheel. Have the alignment checked. The toe should be 0 degrees front and rear for a VX.

That will get you started. Note that the VX does not go into lean burn unless speeds are 75 and below. The engine RPM should be at 2400 RPM at 75 mph. If your RPM is higher, than you have a DX/LX or an Si/EX transmission, and that will hurt mileage.

As always, keep your speed down and keep momentum going as much as possible. If you were getting 43 mpg out of a DX auto, I think you know how to drive one just fine.

[theholycow]

Is there any evidence that the car was modified?

Any driveability symptoms?

[amaterasu71]

Originally Posted by Fetch

The O2 sensor is a wideband 5-wire sensor, and is expensive. I know some of the guys on this site have links to cheap ones online. Others have bought them and they work just fine.

A bad O2 sensor in a VX is usually responsible for dropping the mileage from 55-ish to 40-ish. 29 is terrible for that car. What kind of tires are on it? Air them up all the way to the max sidewall pressure. What viscosity oil (run 5W30 or thinner). Check the plugs, wires, cap, and rotor, and replace if necessary. Check for a dragging brake by jacking the car up and attempting to turn the wheel. Have the alignment checked. The toe should be 0 degrees front and rear for a VX.

That will get you started. Note that the VX does not go into lean burn unless speeds are 75 and below. The engine RPM should be at 2400 RPM at 75 mph. If your RPM is higher, than you have a DX/LX or an Si/EX transmission, and that will hurt mileage.

As always, keep your speed down and keep momentum going as much as possible. If you were getting 43 mpg out of a DX auto, I think you know how to drive one just fine.

thanks fetch, well today I changed the oil, air filter, and found the tires to be inflated to 26 pounds, so I put them to 40psi (44 max)and i checked for dragging brakes didnt seem so be a problem the front tires didnt exactly free wheel but i fugured that was normal as it didnt seem that brakes were causing a prob.. I found the o2 sensor unit was unplugged so i cleaned it outand plugged it in but the shifter light was telling me to shift in fifth and after the car warmed up it started to choke and loss of power so I think it needs replacing. So i hope what i did today will reap some benifits.. Ill let you know... thanks, shawn

[add|ct]

Is the CEL still on after re-plugging in the 02 sensor?

The way to test for this is to drive the car in 3rd gear and 1,500 RPMs for as long as possible(like 30-35 MPH, I cant recall) and hold at 1,500 RPMS...the light will come on if the 02 is bad. Do that at full temp, of course.

VX can feel choked w/ a loss of power when lean-burn is engaged, by the way.

On the other hand, a replacement 02...go for the NGK or Denso on a site like RockAuto or Amazon. $175-$200 are their price range for the correct wide-band/5-wire 02/LAF sensor on the VX. Compare that to $300+ at an autoparts place for a Bosch(now the OE/dealer outsourced part ironically) or $500+ at the dealer itself!

My dealer wanted $630 for it...

I've bought the SG355 model by Standard Motor Products, hard to find. It pops up as 'available' every few months on Amazon, I keep that page bookmarked. It was only $55 or so. Another user with a VX on this site, ben, uses the same SG335 SMP part. Hard to find, but might save you $150.

[IndyFetch]

Another thing...

The VX will only go into lean-burn mode once the catalyst warms up, so short trips are not going to get you good mpg. Winter mileage always dropped to the high 40s at best in mine.

If the car feels extra sluggish and the previous owner unplugged the O2 sensor, I wonder if the catalytic converter could be partially clogged.

[add|ct]

^Heh, I actually suspect as much is the case more my car sometimes.

[add|ct]

Driving on the freeway with headlights on the other night, my RPMs were at 2,500 @ 75 MPH.

[amaterasu71]

Originally Posted by add|ct

Driving on the freeway with headlights on the other night, my RPMs were at 2,500 @ 75 MPH.

well guys I really think that everything on this car is stock but I can tell you that my rpms at 65 are 2500 or 2600 rpms, what should the car idle at becasue its idling over 1000. I know this cars get switched around alot but id be suprised if the tranny was switched ive ordered the o2 unit should be here on saturday so we shall see... where could I look to verify the tranny? thanks

[IndyFetch]

It should idle at 650-700 rpm. The highway revs are too high. That transmission is not correct for the car. I think you have a DX/LX transmission.