Sudden drop in mpg?

My mpg has suddenly dropped to about 15 to 16 from about 20 in the last few months. The only change has been a tuneup and the installation of a new clutch fan for towing, which were both done by a local Toyota dealership. Any ideas what might be causing the change? Oh, the vehicle is a 2004 Tacoma (V6) XCab Prerunner TRD with about 39k miles and has been pampered from day one.

 

Do you happen to be running an aftermarket oiled air filter by any chance? I know allot of people are saying that oiled filters can clog up the MAF censor which can cause a big drop in efficiency

 

try cleaning the throttle body and changing the fuel filter.

 

Thanks for the responses so far. No aftermarket oiled air filter installed. Everything is bone stock. I'll replace the gas filter and clean the throttle body to see if that makes a difference. Any suggestions on cleaning the throttle body? Strange coincidence on the throttle body. It was replaced by Toyota after about 10k miles because it was sticking slightly.

 

i would get some seafoam deep creep and a tooth brush and clean it really good......it will take afew seconds for the truck to crank afterwards, but it will be fine. you will want to spray the tb really good,and you'll notice alot of carbon buildup come out, scrub it real good, till its nice and shiney and no black residue comes out. also, make sure all the spark plug wires are tight.

 

And check your air filter! Also check tire pressure and make sure no extra weight is in the truck or the bed!

 

Just so happens I have a can of Seafoam Engine Treatment in the garage. I'll give that a try first for cleaning the fuel system. The air cleaner only has a few thousand miles on it and still looks good. Nothing is in the bed of the truck. I thought there was an outside chance the new fan clutch (orange) would be the culprit but it doesn't seem to raise a flag to anyone.

 

just to let you know........for a can of the seafoam that you have, run half the can thru the brake booster line, then put the rest in the tank. cleaning the throttle body is a bit different, as the deep creep is a spray cleaner. just fyi.

 

brake booster line? I don't understand.

 

well, any line that feeds the intake, but the brake booster line is better,cause its right there where you can get to it easiest.

its on the driver side.......look and you'll see a big thich disc looking thing, and a rubber line with a small clamp going to it,and it goes to the intake, thats the brake booster line.

 

gotcha ... thanks!

 

here is a brake booster line.....the one in the middle......its off a ford bronco, but its essentially the same for the tacoma....

http://www.supermotors.net/getfile/217842/fullsize/Brake Boster Vacuum Line.JPG

 

What type of a towing clutch fan was installed by Toyota ?

 

Thanks! I'll add that to the list.