So you may have seen my other posts where I have a 2001 Honda Accord EX F23A1 2.3 Vtec w/automatic that is getting horrible fuel mileage (About 14 mpg this winter) and so far I have not figured out why. I will get to that. First though when diagnosing the car this morning I ran it on the freeway and my scan tool told me the ECT was 214 degrees when I got home. I noticed however when I put my hand on the lower radiator hose it was still cold and not warm at all. This seems very very strange to me like the thermostat might be stuck closed. I replaced it a few years ago but Ill replace it again. Can anyone confirm to me if their Accord behaves this way as well or just mine?

Thanks!

 

If your thermostat is stuck closed, I am pretty sure it would overheat pretty quickly after warming up.

Whats the mileage on it? Did the car suddenly start giving bad fuel economy or did it get progressively worse over time? When last did you get decent fuel economy?

What tune up have you done to it? Air filter, PCV valve, Spark plugs, wires, distributor cap + rotor button, oxygen sensor (if needed), checked tire pressure, and bearing noise/grinding?

Are you a lead foot or a extremely conservative driver?

 

So heres an update --

In short the car was getting pretty bad mileage for years now. I initially found my DC sports header had a crack so I thought the oxygen sensor was getting oxygen and reading wrong. Welded it back up and mileage improved after that slightly but Im still only getting 14-15 right now. My wife is kinda in the middle of aggressive and conservative. She drives the car not me. In the summer we got closer to 18 so I wasn't as concerned.
When we bought the car we usually got about 320-340 to a tank so about 22-23 mpg.

I also installed an external MSD coil and SCI ignition box with MSD cap and wires. Installed new plugs and the ground strap was already starting to lose material which I thought was very strange. These plugs have maybe 3k on them. Installed a new Honda upstream and downstream oxygen sensors. Also changed the MAP and air intake temp sensors along with PCV. I have a injen cold air intake kit which I just cleaned. I disconnected the external coil and SCI box 2 weeks ago with no change in mpg. Checking the ignition timing it was spot on with the SCI hooked up and not hooked up.

Anyways last weekend I noticed the lower radiator hose never even heats up much after a long drive. I decided to pull the thermostat out which I changed in about 2006. It didnt appear to be stuck. I looked up another thermostat to be safe and noticed the OEM temp was 170 degrees online. The thermostat I installed was 180 degree. The catalog at Pep Boys said 180 was the correct OE temp thermostat so that must have been why I bought it back in 2006. Anyways I changed to the 170 thermostat and my mileage appears to be much better. The car has alot more power and isnt so doggy. Im thinking the computer must richen up the fuel mixture above 200 degrees to prevent damage, hence thats why my mileage sucked so bad. Hooking my scan tool back up the ECT temp never got above 203 after a long drive where before 212 - 215 was achieved just by going around the block. Hence I appear to be 10 degrees less as I should be. Lower hose is now getting warm but I wouldn't say hot. My wife has only driven about 70 miles so far so we dont have any mpg numbers yet.

Anyone ever have any experience with this same issue? Hard to believe 10 degrees hotter would make such a huge difference in these cars.