I have a problem that no one locally has been able to help me with. If you have time I would greatly appreciate any suggestions you have.
I bought a 1998 Honda Civic HX Auto CVT for gas mileage, I drive 4,000 miles per month. I have been unable to get more than 30 MPG highway (80 MPH). The car came with a CAI and 2" exhaust, no resonator, cheap aftermarket muffler. I had the timing belt/water pump replaced, fuel filter, plugs, plug wires, distributor/ rotor and Primary 02 sensor. I also cleaned out the EGR ports that were completely clogged. When the 02 sensor was replaced a crack in the exhaust manifold was discovered and a header was put on. The car is also currently without a cat. The gas mileage has not changed for the better following and of these events. I have a scan gauge. The MAP runs around 11 at 80 MPH 3400 RPM. A friend looked at the fuel injectors when the EGR system was replaced and said they looked to be in very good condition. I should also mention the car burns about 1qt of oil every 1000 miles. The PCV was replaced also. I am currently running 15w40 mobile one synthetic oil. I am basically out of options. I am considering putting on a fuel pressure regulator, thinking that the ECM may not be able to adjust for the increased air intake but have no other ideas. I read that the lean burn engine can run as high as 19:1. I believe the car should be getting 38 to 42 MPG on the highway. I got 27 today with the A/C on. The car also has new tires/ alignment. I've also adjusted the timing from 10 to 14. The Honda repair manual states 12 +-2. This had little affect. I should also mention that the car rarely runs in closed loop at speeds over 70MPH. I have a V8 Lincoln LS that gets 24 on the highway. This civic mileage really stinks. I should also mention that I am only concerned at fuel economy and performance is of no concern. Any ideas?

 

if your burning that much oil, there could be a problem with the rings, or valve seats. it could be losing compression and that could cause power loss and less fuel economy. get a compression test and a leakdown test, they can tell you if anything is wrong. other than that i have no clue

 

Thanks for the idea. I've also considered a possible ignition problem although the car runs smooth at lower speeds. If the compression is off would a rebuild or replacement be the way to go? Would low compression cause high MAP pressures? Anyone know if my ECU will work with other engines or would that have to be replaced too? Maybe the transmission while I'm at it too? I've heard a lot of complaints about the CVT transmissions although I have no complaints yet. I suspect most of the problems people have had have been related to incorrect fluid being added. I was in a pinch once and took my car to get the oil changed at a non Honda/Acura shop (normally do it myself) ...stopped one of the guys from "topping it off" with regular non Honda fluid! It wasn't even low. I suspect most CVT owners don't understand the importance of correct fluid. Maybe just find another civic and use this one for parts? LOL

 

yeah, cvts are a beast i would never mess with and you are right about the correct fluid. if it is bad rings, you could get a used engine or rebuild for more power, but i don't know how much a cvt can take.