What's up HAF!

I have a 96 accord lx a/t purchased almost a year ago with 180k miles, before my mpg was doing good, 30-36mpg on the highway, but now i noyiced as my mileage goes up yhe mpg is going down.

When i got the car I replaced trans fluid 8 times, coolant 3 times, new belts and WP. New sparkplugs oem. New brake pads and bnew tires. I cleaned egr ports and injectors. New air filter element.

Now, my problem is im getting worse mpg onyhe highway, only about 25-26mpg goong 70-75mph. No passengers, a/c off.

What could be wrong? Is changing my fuel filter help case? Desprate to fix this problem since im using the car everyweekend for a drive from norcal to socal.

Any help would be very much appreciated. Please ask questions if my statements are not clear. Thanks again and more power

Current mileage: 194,987 miles


AccorDats

 

Dragging brakes? Change em yourself? Clean & grease the caliper slide pins? OTOH if you're driving long highway miles with dragging brakes you'd probably smell em and notice the heat.

 

Upstream oxygen sensor ever been changed? They tend to get lazy with age & mileage.

 

Jimblake> no dragging on brakes sir, no unusual sound nor severe brake dust, the car can cruise normal on downhills. Yes, i changed pads myself and cleaned it properly. Thank you for your reply, any other suggestions?

Roader> o2 sensor never been replaced, is there any way i could check if it is failing? Or needed to be replaced? Thanks sir

 

While it isn't "supposed" to happen that O2 sensors both enter failure mode and don't throw codes, there have been too many reports from Honda and non-Honda owners alike that say that replacing the O2 sensors cured issues with poor fuel economy in high mileage cars.

 

Sure. Check out youtube SuVs4T-c_I and 24Rp7BghSLM.

@ almost 200K miles, though, I tend to think upstream O2 sensors as a maintenance item and they're not very expensive. One of this site's sponsors, TheAutoPartsShop.com, lists a Denso sensor for $44 shipped free. I think it's P/N 234-4620 but double check that part number.

 

The O2 sensor can get lazy for awhile before it gets bad enough to set off the check-engien light.

I think its only the upstream sensor that has any authority over fuel rate.

 

Thanks Roader, Jimblake and shipo, really appreciate your replies.

I will go and order an upstream o2 sensor, good thing its not that expensive. When i get to install it i will get back and write an update about my mpg i hope this will do the trick.

Thanks again HAF

 

If you drive where there's any salt on the roads, check your fuel lines for possible leaks. They corrode and pinhole w/ exposure to road salt.

Also check the injector/fuel rail oring connections for possible leaks. You can usually smell this leak, but hands on can detect a small leak.

Fuel pressure regulator diaphragm can fail and allow raw fuel to be pulled into engine via vacuum reference line. Pull reference line and smell. If you smell gas, the diaphragm has ruptured.

OTOH, your miles of 26 mpg at 75 mph doesn't sound terrible. I think you earlier results are on high side.

I feel my 94EX (245K miles) is in good shape, and I can get slightly over 30 mpg on straight highway driving only, but closer to 25 mpg for my commute which is 16 miles w-way, w/ about 1/3 street and 2/3 interstate and variable speed. It's been that way for years.

good luck

 

AccorDats,

Just calculated mine this morning, and am at 26.9mpg on a 153k mile motor. that's blended city/hwy on a 5sp manual.

As suggested, measure over several tankfuls. Will change from cold temps to warmer temps as well (air density / drag).