Hey everyone as the title said I'm have a huge drop in my mpgs. I have a 1981 accord lx. I went from getting 38-40 mpg highway down to 26-28 mpgs. Nothing has really changed in my every day driving. I commute about 30 miles one way to work 5-6 days a week all freeway. The motor does make a strange sound when first starting it in the morning only. Almost like a low pitched whinning noise.

Any ideas? Maybe adjusting the carb? If so how and what. I don't have a great knowledge of Honda carbs.

PS a full tune up done 10k ago timing belt/water pump done about 6k ago.

 

doesn't sound like a match to me.
Are you the long term owner or is this the first winter?
My mpg go down in winter ...

 

This is my first winter with it. But do you think it would be that huge of a drop?

 

Carbureted engines are far more sensitive to cold air temperatures than are fuel injected engines, and when it gets colder than 40°F they start to exhibit fuel atomization issues; the further below 40°F it gets, the worse the fuel economy will get.

FWIW, also unlike fuel injected engines, carbureted engines need a clean air filter for best fuel economy; have you changed the filter since you bought the car?

 

Yes I changed it about 10k ago when I did the full tune up. I guess I just have not noticed in any of my other cars that have a carb that big of a mpg loss.

 

It's more mpg loss than I see with fuel injection; I have colder typical winter temps than you do.

... could always wait until the return of the season when you bought it and see if you get the original mpg back.
Luck.

 

A sticking choke will cause excess fuel consumption. Look for black smoke from exhaust pipe and poor idle when warmed.

good luck

 

I have not noticed any abnormal smoke from the exhaust. If anything once the car warms up (10-15 minutes) the rpms kick down to about 850-900. But looks like I will just wait it out see if it gets restored in the spring or not

 

You can visually check for a sticking choke. Just look to see whether your choke plate opens up properly when the engine warms up.

Rule out any of those things one-by-one.
- dragging brakes?
- suspension alignment?
- low pressure in tires?
- etc...

 

It takes ten to fifteen minutes for the car to warm up? Yikes, that's way too long. Have you changed the thermostat recently? I'm thinking if your car is running so cold for so long, it is also by definition running very rich for that same period of time. If an engine hasn't settled down to its normal warm idle RPM within five minutes (should be even less) then something ain't right.