1989 740GL 4D SEDAN

I'm getting a strange noise from my car, and It's frustrating to no end. I only hear it at idle, but it may be there all the time. (Engine probably drowning it out.)

It seems to come from the center console, and it's a buzzing. It's similar to the sound when you turn a power steering wheel too far. It's not that, but that's similar to the sound. I still have the problem where the air only blows from the defrosters, but I don't care about that. (Only mentioning in case it's connected). Sometimes the sound is constant, and sometimes it pulses. Sometimes when I smack or kick the center console, it goes away for a few seconds. Any idea what this could be?

I'm still getting horrible milage too. Not sure if that's connected, but I just keep getting ripped off by mechanics. I'm not sure how big the tank is on this car, but it should take me more than 160 miles. Thanks for any help.

Don't know about the buzzing but the gas tank is more than likely 60L (could be 80L if you live in europe) but either way that is 1)horrible or 2) gaustly horible gas mileage (specs: 20mi/usg-city & 24mi/usg-highway for auto 230f). When have you last done a tune up? Cheap fixes include changing out the plugs and wires and if you have over 100000 miles on the car, change out the o2 sensor as well. Then check the FAQ for more tune up info.

Maybe testing the Fuel pres. reg. would be in order too since it might be causing the injectors to be dumping too much fuel when not necessary.

Good luck,
Tim

ps. I get ~ 430km or about 270mi per full 60L tank - mixed city driving.

Had the same problem on my 740,take out the glove box, behind it you'll find a relay for the A/C, take it out and resolder the contacts

I'll try that. What color is the relay? Are there instructions anywhere on removing the glove box? Note, this happens whether or not I have any type of ventolation turned on.

About the other reply..

See, I think I'm being ripped off. I've had the following done at the same time from the same mechanic:

Timing belt replacement/adjustment
New Belts
Rear Differential Sealed (not familiar with this. said it was leaking)
Rearrange (EKG EGK?? Something like this) Hoses
Adjust kickback cable
Fuel Filter
Tune Up
Oil Change
New O2 Sensor

I feel absolutely no difference, and the only thing I can verify is the kickback cable, because I can feel the difference. The car still runs as rough as before and has the same horrible milage. I also had another mechanic tell me I don't have a vacuum reservoir at all, but my friends tell me that's silly.

Edit: I'm in the US. What is my tank in Gallons?

There is only one relay back there and it's black,cant remember the dismantle but think there is a screw or two in the box and two or three hidden under the dash ,just check around.if you have a sensor on the dash be carefull not to damage it,cause the wires run over the top of the box.

This didn't seem to help, but I did realize something. The noise NEVER happens on a full tank. This leads me to believe it's the fuel pump. Where is the pump located on this vehicle? I've been ripped off too many times recently, so what should I expect to pay (US) to get this replaced? Thanks.

Some things I've learned from personal experience with my '87 GLE. 1) If your distributor is like mine and is between the cylinder head and the firewall, the internal hall sensor can break loose in higher mileage engines. Pop the hood and take a listen. It will make a similar "buzzing" noise if it comes loose and will kill mileage and make your car run like crap. Easiest fix is to replace the whole distributor assembly (NOT just cap/rotor) yourself if you can. A knowledgable shop can replace either sensor or distributor for you at about the same cost. (What you save in parts, you pay in labor). 2) Check the condition of your wiring under the hood. If the insulation on your wires are cracked/sticky/missing you're open to a whole host of gas eating, performance killing gremlins. Fortunately, should this be the case, you can replace the entire engine wiring harness as one unit. Unfortunately, the harness costs about $550 ITSELF thru a dealership IF you do the install yourself.

Other thoughts: You have 2 fuel pumps. One in tank, one under the car on the drivers side; The damper flap for your a/c system (the part that changes which vents air comes out of) is driven by vacuum from the brake booster I believe. If it doesn't hiss when you move the lever, check for a loose hose under the dash; Your gas tank is 13.5 gal. US.