Lousy Fuel Mileage

FiveOJoe · 02-21-2012, 04:59 PM

I just had to fill the tank for the 2nd time since getting my 944s. The first time I thought it was a fluke and I didn't get it full before resetting the trip meter. Today I filled up again and after topping off, I'm getting 15 miles per gallon. Half local and half highway 60-65mph, never really hammering the tach and shifting at 3000-3200. Car idles unevenly @ 1000 and 1500, but I don't think that accounts for all of the loss. The only other symptom is black soot on the bumper above the exhaust.

Any common culprits I should start with first? Thanks.

alan6272 · alan6272's Garage

Even though mine is a 83 I had this problem and found it to be my coolant temp sender to have a bad connection causing my car to run rich. I found it by watching videos on you tube and it was a newer car than mine. Good luck. Also check the air filter also a common over looked item.

mytrplseven · mytrplseven's Garage

Yeah, look inside the air filter:

This was mine after I bought the car and drove from Santa Fe to SW Florida. Still got 30mpg. The mouse got out at Albuquerque.
Also recommend doing a thorough vacuum system check. I did mine with a 2" PVC fitting stuffed into the J boot with less than 10 psi into an air fitting screwed into it and spraying soapy water over everything. Bubbles are where your vacuum leaks are:

racer · 02-22-2012, 06:38 AM

Compare Side-by-Side - indicates that a recalibration of period fuel milage stats gives the 944S a rating of 17 city, 24 highway

also:
1) have you done a tune up yet? plugs, wires, filters etc?
2) Wonder how the NJ "winter" gas is... ethanol content etc
3) Black on the bumper implies a richness... which would also mean burning too much fuel

Are you getting a full tank in there? 20 gallons?

FiveOJoe · 02-22-2012, 05:56 PM

Everything is clean and new as far as plugs filters, wires, fuel filter etc. I wasn't sure I got it full the first time when it showed 15, but I was at 15.1 the 2nd time around and it took 18 gallons, so yes, I'm getting it topped off.

Not pushing the car hard and shifting early, getting to 5th as soon as practical on the highway. Car drives very stong and crisp, doesn't feel like it's that "fat." Can't find any vacumn leaks.

Does an 'S" typically get a lot less mpg than a non "S"

I was hoping for a lot better MPG than 15, especially driving it easy.

Can some of you guys with and S car's give me your results?

alan6272 · alan6272's Garage

15 is way to low no matter s or not. I get 27mpg with mine. When my temp sender wire had a bad connection I went down to around 15 and the car idled very poorly as well as black smoke at the tail. A bad flow meter bellows I believe will cause this as well, and may not be easy to see just sitting as the torque of the motor could oped such a crack etc. just some ideas to look for.