Cold weather= crappy gas mileage

[Madd Hatter]

93 SHO ATX, crapload o' miles. Have had this problem since I owned it. When the weather's cold (sub 40 I'd say) my mileage goes from 330-360 a tank to 280 if I'm lucky. Last winter I noticed my RPM's were running 3200 or so at 65 instead of 2500 they normally do. Higher RPM= worse mileage, ok. But WTF do I do? Sometimes after the car got warmed up, it'd drop back down to normal, but it was never a set time. Sometimes it'd drop back to normal then go back up again later! I've tried letting the car warm up before I drive it, that doesn't seem to be doing me any good.
Is this normal?! Is there some cost-effective way to solve this or do I just put up with it?

I guess I should be happy my car's running all the time in the winter (knock on wood), and gas mileage isn't the least of my concerns.

 

[projectSHO89]

Run the car through the KOER tests to see if there is anything that the computer sees.

For some reason, it sounds like your transmission is either not shifting into overdrive or the torque converter is not locking up.

This might be due to a cold-sensitive mechanical fault in the transmission or may be due to a bad electrical connection that manifests itself when it gets cold (for example, an electrical contact that looses connection due to cold-induced contraction).

Steve

 

[HopefulSHO]

Ya, it will longer for your tranny to warm up to normal temps when it's cold, so it won't lock the torque converter until it's at a certain temp. I also read somewhere that the 'winter' formulation of gas gives worse milage than a 'summer' fomulation.
This is just speculation, IHNC what they do to gas, but I have heard they do change it for the different seasons.

 

[sdpatt]

Is the engine temperature getting up into the NORMAL range? If not, you have a leaking thermostat seat and the effects of the rich, open loop engine control mode.

 

[billh]

Back in the dark ages, when cars had carburetors, we used to make gains in fuel economy by fixing the hot air door sensor on the factory air cleaner. The hot air coming off the exhaust manifolds made a difference when the weather was cold. Yea, I know that fuel injection nullifies that, but I would be curious to see if getting a little warm air into the engine would make a difference in cold weather mileage. Mine and my AWA's car get poor mileage this time of year.

 

[Petersho1]

I have the same problem, as I known it`s popular in ATX. Thats what worry me is that is droping and going up in the same drive. For me 3000RPM-70MPH to 2500RPM-70MPH and again and again.........And after a couple days- check my topick <engine stopped working at 30MPH.Guys are saying thats CPS + maybe TPS.I'm getting sick of it.

 

[Petersho1]

It cut me.. topic engine stopped working at 30MPH

 

[haydenm315]

Madd Hatter:
93 SHO ATX, crapload o' miles. Have had this problem since I owned it. When the weather's cold (sub 40 I'd say) my mileage goes from 330-360 a tank to 280 if I'm lucky. Last winter I noticed my RPM's were running 3200 or so at 65 instead of 2500 they normally do. Higher RPM= worse mileage, ok. But WTF do I do? Sometimes after the car got warmed up, it'd drop back down to normal, but it was never a set time. Sometimes it'd drop back to normal then go back up again later! I've tried letting the car warm up before I drive it, that doesn't seem to be doing me any good.
Is this normal?! Is there some cost-effective way to solve this or do I just put up with it?

I guess I should be happy my car's running all the time in the winter (knock on wood), and gas mileage isn't the least of my concerns.

I've got a 93 mtx that I just recently got back on the road. The car was down for 60 days for 60K, shoshop ud pullies, and stage II cams. I used to get between 330-380 miles depending on how much my highway mileage fluctuated. I'm getting about 260-280 before the light comes on. I could probably push 300 out of it but I'd rather fill than burn up the pump. I think the cams may eat some gas. My idle is pretty strong right now as well. I also put redline fuel system cleaner in. I wonder if that stuff alters mileage.

 

[jbeano]

Up here in the great white north the winter formulations of gas suck. It seems that they put up to 10% ethanol in the mix to keep the gas line from freezing and thus also lowers the btu potential of the fuel. Other factors to decrease mileage is longer periods to warm up and the heavy draw on the alternator running the fan and full lights.