Help! Im Only Getting 150 Miles to a Full Tank of Gas

I just got my car back from being painted in the shop, and now I am burning through gas like crazy! I pulled codes with peake and the only code im getting is "coolant temperature plausibility". I changed my coolant temp sensor last week, erased it and its back. I have searched and I see this code looks like it is for thermostat. Could this be my problem? I have also noticed when i pull into my garage it smells like fuel. The smell is coming from the exhaust pipes, so Im guessing something is telling my car to run rich. Im positive it was not doing this before I dropped it off at the shop. If I could please get some help it would be greatly appreciated. Thank You

Ride with the MAF out for 25 miles or so. Do the math and see if it helps.

There a lot of complains about body shops smashing ecu/ground wires with fenders etc.

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Thermostat. Drive on highway...you'll see your temp needle drop slightly to the left of center. With any luck, maybe they just unplugged the therm, but that will cause you to get horrible gas mileage and that's what I thought before I saw you had a therm code!

Originally Posted by J1Productions

Do not do this. It caused my transmission to go into limp mode and had to pay 50 bucks to get the codes read and reset.

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As soon as you plug the MAF back in, the transmission should go back to normal. I've done it many times.

So have i.....it diagnosed a lot for me. And your transmission doesnt go into limp mode.

Originally Posted by dmax

Thermostat. Drive on highway...you'll see your temp needle drop slightly to the left of center. With any luck, maybe they just unplugged the therm, but that will cause you to get horrible gas mileage and that's what I thought before I saw you had a therm code!

This is what I would do first. Part is pretty cheap, work isn't bad. Go ahead and replace the entire coolant system if it hasn't been done yet. You should know the drill by now.

I'm with DMax, a cold engine = sh!tty gas mileage.

Originally Posted by Drewfus2101

This is what I would do first. Part is pretty cheap, work isn't bad. Go ahead and replace the entire coolant system if it hasn't been done yet. You should know the drill by now.

Why not use the hidden OBC first to see if the coolant is getting up to temp. The needle may show center, but center is 75-105 Celsius. I agree with dmax however, cold engine means shitty mileage.

I agree with me also...but I have to say also that mpgs have been discussed before many times...use advanced/title search for 'mpgs.'

The cribs of the collected mgp wisdom:

air filter, fuel filter, plugs at 100K

small intake leaks (though they usually throw a code...they often don't throw a light)

...and then all the other things we do to keep things tight...vcg, ccv, new o-rings and rubber wherever you happen to be (though, at 237K miles, all my vac hoses were intact...they just broke when pulling them off of their nipples).

Therm and fuel filter together gave me 3 mpgs...about 1.5 better mpgs for each replacement.

Also, rather than report your miles per tank, average mpgs at an average mph 'on' a tank is a much better gauge.

I know I get 'around' 22 mpgs when I've done 'around' 250 miles at an average speed of 25 mph. I get 34.5 mpgs when going for a long run on the highway at 71-2 mph (it's downright dangerous in NJ/NY to maintain only the speed limit!) in fifth, in cruise. Anyway, just saying, so you have a reliable measure to compare your work against.

Originally Posted by ptrcd003

As soon as you plug the MAF back in, the transmission should go back to normal. I've done it many times.

I had to get the code reset I drove about 70 miles with the gearbox code and it did not go back to normal.

Originally Posted by ChrisRedmon

So have i.....it diagnosed a lot for me. And your transmission doesnt go into limp mode.

Yes it does. For my car at least it brought up a Maf gearbox error code.

Originally Posted by J1Productions

Do not do this. It caused my transmission to go into limp mode and had to pay 50 bucks to get the codes read and reset.

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Dude. Buy yourself a scanner and read/reset them yourself.

Originally Posted by SteadyMobbin

Yes it does. For my car at least it brought up a Maf gearbox error code.

A what? A MAF gearbox code? Someone has been pulling your plonker mate. Seriously. There is no such code. MAF is an acronym stands for Mass Air Flow. It is a sensor that fits between the air intake and the throttle. Absolutely nothing to do with the gearbox. I am not even aware of any sensor on the gearbox that would throw a fault code. There are certainly none in the BMW fault code PDF I use as a reference. Print this document off, take it round to the guy who stiffed you and get him to point out the "MAF gearbox" fault code that he reset for you. Then ask him for your money back.

http://www.kneb.net/bmw/E46/E46%20Trouble%20codes.pdf

Originally Posted by J1Productions

Do not do this. It caused my transmission to go into limp mode and had to pay 50 bucks to get the codes read and reset.

Sent from my SCH-I500 using Bimmer App

^^ dont listen to this guy.

OP check the thermostat like said above, either in the Hidden codes or check the connection in the engine bay. If you havent already, you might as well just replace the entire cooling system. You will need to eventually especially if your car is a higher mileage car

are you absolutely sure your mileage is that bad? that means you've dropped to like 10 mpg!
When you get to an empty tank, does your car take 15 gallons to fill?

OP,

Was it just painting work done.. Any painting in the engine bay?
Or, was there also body work? Any welding??

How many miles is on your M3?

Sound like you boosted

Originally Posted by dmax

Thermostat. Drive on highway...you'll see your temp needle drop slightly to the left of center. With any luck, maybe they just unplugged the therm, but that will cause you to get horrible gas mileage and that's what I thought before I saw you had a therm code!

What if my temp gauge rises slightly on the highway?

The trans controll module gets its load signal from the MAF sensor. Do not unplug your MAF and drive around.