Ill start with the problem that's been occurring the longest. Here goes.

Terrible gas mileage! I have done absolutely everything to help it, o2s, fuel filter, spark plugs, air filter, tire pressure, cleaned MAF, EVERYTHING! If anything, it is getting worse... The mileage has dropped to about 14.5 in the city over the past year or so, so it's not a seasonal thing. I used to get 17.5 around town. It's an M6 with a fairly new clutch, and a good tune. I've had the tune for over two years, and tunes cant go bad so that's not the problem.

Hard starts. Maybe 1 in every 4 starts it will take several seconds to start. I've already tested the fuel pressure and found that when I turn the key on it spikes to 60psi then falls to 55 immediately, then after a couple seconds, falls off down to zero (which takes about 45 seconds).

Idle problems. Most of the time, whether the engine is hot or cold, when I slow down to a red light and I push in the clutch the rpms will hang around 1300 for a few seconds. After i come to a complete stop and wait 1 or 2 seconds it drops to the normal 800. I can even sometimes be in 4th gear at about 30-35 and let off and not decelerate, the car is just being pulled...

A/C stops blowing after a long period. Okay so here in Texas it is about 100 degrees everyday, and driving to and from college (about an hour and a half) i run my a/c on full blast. After about 45min to an hour into driving my a/c stops blowing hard, full blast feels even lower than the low speed. However, I can here the blower motor working as hard as ever, maybe even louder, but the air just isnt passing through the vents...

Random SES lights, most of them being lean codes in banks 1 and 2... They go off in a day or two, but maybe come back a couple times during the week.

Bad squealing coming from the front left wheel. It started off being just a short, but loud squeal when i would brake at low speeds and turn. Now it will squeal on bumps and if i make slow turns even without applying the brakes... Im thinking it's the wear sensors on the pads, the rotors are really warped and I will be doing a full brake job soon.



Any input greatly aprreciated, thx guys.

 

Sounds like a bad vacuum motor in the dash. The doors in the vent. box are controlled by these, and when they start to go the doors will sometimes be in weird positions. Could also be the connection on the back side of the temp control switch, which is actually a vacuum porting valve, or the switch itself may be puking. Same with the heat/vent/A/C switch.

 

for the ac check the vacuum lines at the back of the intake. my was doing that and a vacuum hose was not connected.

 

Okay cool. Where is the temp control switch at?
So it could've just popped off randomly? I haven't taken off my intake in a while but maybe i didn't get them all connected really well or something.

 

The one in your dash...with the heat and A/C controls.

Possibly it came off, but not likely if you haven't been in there messing around. It's probably in your dash.

 

Wow. Here's ur sign.... lol

 

A vacuum leak would also go a long way towards explaining your high idle issues, as well as the SES codes that you are getting.

 

/Agree

Would explain the bank 1/bank 2 Lean codes.

 

Okay cool, ill check for leaks today.

Any ideas why my fuel mileage is suffering? Or the hard starts?

 

Bump.

 

Alright guys i found the vacuum leak. The little hose that runs into the intake manifold behind the throttle body on the passenger's side had a hole in it. I think it's part of the a.i.r. system? So now my idle is fine and hopefully ill get a little better gas mileage and no more codes.

 

Bump for hard starts and horrible gas mileage!

 

I've experienced the same terrible drop in gas mileage. I used to get around 18mpg also, and then it dropped to somewhere around 14-15. On the best days I would get to around 80-90 miles until the needle crossed the 3/4 full mark, and on this current tank it was only 55-60 miles.

I plan on changing the fuel and air filter and possibly doing the spark plugs and wires too. Hopefully it helps....

 

Yeah same here. I did all of that plus the o2s and i kept getting worse... Hope you have some better luck.

 

You wouldn't happen to be running ethanol gas would you? You'll see a mileage decrease even with the 10% stuff.

 

Yes but I have been for a long time. I have seen the decrease in fuel mileage while using the same type of gas from the same station for over a year now. (This is tluzls1 but just my other account btw)

Im gonna warranty out my o2 sensors for some new ones just to see if that's the problem. I might as well since it's free. They are bosch 13111 o2s btw.

 

Ever think its maybe the cats? I don't see what else it could be....

 

I've wondered about them but I just don't know of a way to tell for sure. They are the magnaflow cats that come in the tsp catted y-pipe and they're about 2 years old. I don't know if those particular cats are prone to clogging or not? Any symptoms of bad/clogged cats?

 

I think you have to have a muffler shop measure D/P across them by drilling a hole in them.

 

Bump. Still hard to start and still bad gas mileage. o2's are brand new.

Could the starting problem be a bad fuel pressure regulator? I have a fuel pressure gauge to hook up to it, but im not sure what the pressure should look like during the test. It spikes at 60 when i turn the key on then falls to 55 immediately, then proceeds to steadily fall off to zero (takes about a minute to get to zero).