Bad gas mileage

Rick Lee · Rick Lee's Garage

I'm a few hundred miles into my newly transplanted 3.2. It was rebuilt 8k miles before I transplanted her into my car. I haven't filled the tank up completely yet. But I usually fill it to the halfway mark and I'm getting to about 110 miles before the low-fuel warning light comes on. Granted I take her to redline every single chance I get and I drive excessively fast when no one else is around. But why is this mileage sucking so bad? I think I was getting well over 400 miles to a tank before my old 3.2 got sick. I just had the fuel line replaced. I replaced the fuel pump myself in August. When I start her up in this cold weather, she smokes a little and it lasts a few minutes. The other day I was shifting into 4th at about 6500 rpms and I thought I saw a puff of smoke in my rear view mirror. But it may have just been a puddle I ran through. I didn't see that happen again. I don't notice any rich gas smell when I sit at red lights. I had her on a lift this Sat. and saw no leaks at all. What's up with this horrible mileage? Thanks.

Embs · Embs's Garage

A bad or non-existent O2 sensor can make you run rich and burn through the gas. Also bad injectors /injector spray patterns can suck the gas. Have you noticed any smoke / fumes from unburned fuel?

Rick Lee · Rick Lee's Garage

While my car does not smell like new leather inside, it doesn't have that unburned gas smell it used to have when my old 3.2 was running severely rich. It doesn smell a little like oil, but I was overfilled until Sat. and I alwasy have the heater on.

A few other things - I replaced the O2 sensor in Sept., I have had a cat by-pass since August, I have Webcams, I replaced the cyl #4 fuel injector when I installed the new engine. Next weekend I will pull the dipstick and try to light it on fire to see if there's gas in the oil. I'll stand away from the car when I do this.

VincentVega · 03-03-2003, 11:31 AM

Richard-

I am curious what the specs of the cams are. Also, are the plugs nice and clean?

UTKarmann_Ghia · 03-03-2003, 11:32 AM

I'm having a similar problem. I picked up my car 2 weeks ago from Little Rock, AR and on the highway it got 23.5 mpg. I thought this was a little low since I did not speed on the way back as I didnt want to get pulled over with no tags. And when I got into Denver (high altitude), I went through my first half tank of gas in 100 miles. That's about 13mpg! Since then I've replaced the o2 sensor, but I was under the impression that it only controls emissions at idle thru like 2,500 rpm. I'm getting a bit better mileage now, but not mid 20's as I'd expect. Is this high expectations for my 3.0 liter engine?

I'm gonna run some Techron through her to clean her out and measure again...not sure how that will help.

Are you kidding about lighting the dipstick!?

Rick Lee · Rick Lee's Garage

My Webcams are 20/21.

I just spoke with a shop and they said I should be getting worse mileage in this cold weather and with a more powerful 3.2. I don't remember getting bad mileage last winter.

VincentVega · 03-03-2003, 11:55 AM

My *guess* is with the cams and the crap gas we get in the winter your mileage is within reason. Have fun!

Embs · Embs's Garage

I find that hard to believe, all of my cars, turbo or NA love the cold oxygen rich air.

kstylianos · 12:16 PM

Richard,

Check the local board. Thought I saw someone who posted they had a small portable gas analyzer. May be worth a test to see if you are running rich.

http://www.dorkiphus.com/porsche/viewtopic.php?t=45