GenVibe - Community for Pontiac Vibe Enthusiasts

Hey Everyone,Just to warn you, I'm not much of a car guy. My maintenance skills top out at changing spark plugs and serpentine belts. My 2005 Vibe (Base, manual transmission) fuel economy has been dropping over the last few months. I was getting around 34-35 average MPG, and now I'm down to about 29 MPG with the same driving habits/patterns. I have 105,000 miles on my baby.I have new spark plugs, no CEL's, no lack of power, clean air filter and clean MAF sensor. Tires full of air. Everything appears to be fine, except for the fuel economy. It has gotten cold outside recently (Michigan) and I usually drop a LITTLE in fuel economy over winter, but not like this.Any ideas on where I should look? My gut is that catalytic converter is questionable, but I don't see the usual power loss and sulfur smell. Any good way to tell?Thanks!Jimmy

Oh, one last thing. I do see the engine RPM's higher at idle now (even after it warmed up), around 1100 - 1200 RPM where it used to be around 800 RPM. Could be due to cold weather, though.

I am having the same issue but I do have a CEL because of poor catalyst efficiency. It makes my car idle higher when cold but goes to normal once warmed up. Mine is running near 2000 rpm. When cold. I think the CEL is keeping it in open loop mode and richening the mixture. My mpg. jumps around a lot in the winter from 22 to 29 ??

29 mpg for a Vibe that has 100,000 + miles on it during the winter is normal due to:1. High idle until engine warms up2. Winter Fuel3. Use of Defroster Doubt your Kitty is bad

I have had two 1.8L AT Vibes - typical mileage (in part due to mostly non-highway driving) has always been about 24-25 mpg. Winter is worse.

Quote, originally posted by jimmycrackcode » I'm down to about 29 MPG with the same driving habits/patterns. Sounds normal!Did you recently install winter tires?

try doing a seafoam treatment and see if you notice any difference. couldnt hurt and its not expensive.

...winter gasoline has lower energy [BTU's] content, due to having to up volitility for cold weather starting.