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2003 Buick LeSabre; lost gas mileage, and gently vibrates.

gifrongifron Posts: 9
edited January 17 in Buick

I've been driving this car for nearly a year. I replaced all the wheel hubs with new Moogs several months back, so I don't think that is associated with this problem.

I recently went from 28 mpg, to about 23. At the same time, I noticed that I often have a gentle vibration when accellerating. If you've ever driven over a worn brick road, that's what it feels like. And it's not consistent; I took my brother-in-law for a ride to get his take on it, and could hardly feel it at all. Vibration is in the seat and floor, not the steering wheel. It is more noticeable when hitting dips in the road.

Engine, transmission, suspension? What do you think?

Comments

  • gifrongifron Posts: 9

    Yes, this is embarrassing to admit, but maybe it will help someone else. Okay... Air pressure was low in all four tires. Apparently, because I have indirect TPMS, I got no indication of low pressure. Guess I should rely less on the dashboard, and more on a gauge.

  • Kirstie_HKirstie_H Posts: 10,914

    @gifron said: Yes, this is embarrassing to admit, but maybe it will help someone else. Okay... Air pressure was low in all four tires. Apparently, because I have indirect TPMS, I got no indication of low pressure. Guess I should rely less on the dashboard, and more on a gauge.

    Not embarrassing at all. I'm sure every one of us, at some point, has overlooked the simple or obvious causes. Not too long ago, I thought I had a transmission issue because the vehicle barely moved when I put it in reverse and hit the gas - apparently, this can happen if you fail to fully release the emergency brake. :) Glad your solution was easy and CHEAP!

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  • gifrongifron Posts: 9

    Actually, it's still a problem; just ignore the gas mileage part, as properly inflated tires took care of that. So to repeat the problem, it recently started a "soft vibration" while accelerating. It feels kind of like driving over a worn brick road - the vibration is there, but not very pronounced; although one particular day, it was actually pretty rough (perhaps because of the especially high humidity that day?). It happens at all speeds. I think it is always there (when accelerating) in the background, but it is especially noticeable when I drive over a small dip in the road, putting extra downward force on the suspension, etc... Gas mileage is fine. Power is fine. Tires look good. Changed all four wheel hubs and rotors several months back, shortly after I bought the car. Any ideas? Thanks.

  • capriracercapriracer Somewhere in the USPosts: 798

    gifron,

    I'm guessing a CV joint is gradually going out.

  • imidazol97imidazol97 Crossroads of America: I70 & I75Posts: 18,460

    @gifron said: So to repeat the problem, it recently started a "soft vibration" while accelerating. It feels kind of like driving over a worn brick road - the vibration is there,

    Is it a high frequency vibration or a slower speed matching the rotation rate of the wheels? Does it occur on very smooth roads on a slight downslope with no pull on the front wheels affecting how they strain against the bushings on the suspension arm? Does it occur in 3rd as well as 4th? In 4th these engines are very sensitive to misfire at lowest speed after the torque converter does its 99% lockup maximum. This will quit with opening the throttle or if in 3rd instead of 4th due to the lesser load on the engine with the gearing.

    If there's any chance this frequency matches an engine miss, have good spark plug wires been put on after 10 years? I'd recommend AC Delco from rockauto.com for a good price. Are the plugs the iridium AC Delco plugs?

    @gifron said: Tires look good.

    Talk about the tires? Brand, age, miles, rotations? AND when was the car aligned? These cars were sensitive to tire quality and brand. If you find any reason for this to be tires and it's a lower frequency rate, RoadForce balancing is recommended using a Hunter 9700 or upgrade equipment to do it. And you need to have an alignment that is spot on.

    If there's any change the tires have a part in this, my diagnosis would be to rotate the tires back to front, doing one side at a time, and see if there's a movement of the vibration? I would be suspicious of tire wear or hardening of the tread having put a small uneven wear pattern onto the tire.

    You also need to check the tire rod ends and the bushings on the suspension parts on front and rear. Because you feel it while accelerating, it might indicate front. Or it might just be you are feeling more vibration through one of the engine mounts. How's the transmission mount on the front toward the radiator? Those are liquid filled, I'm told, and they can go bad.

    Also, have the injectors ever been cleaned? I had an injector problem at 150K mi. Indication was a flash burn on one side of the spark plug. New plug, new wires, still occasionally missed and cleared. Eventually set light again. Took it off and switched places, but it had a lot of gunk in the intake of the injector. My quality shadetree neighbor indicated that was not good. I used a couple runs of Techron fuel system cleaner by Chevron. They also make an injector cleaner. Follow directions: run tank low, and then fill after inserting cleaner with premium quality fuel, which also has good cleaners to assist the Chevron cleaners.

  • gifrongifron Posts: 9

    imidazol97,

    High frequency, not matching tire rotations. Vibration occurs at all speeds, and in all gears. Plugs and wires probably need to be changed, but it does not seem to be an engine issue. I have run injector cleaner through in the not too distant past.

    Additional information I noticed just last night - Vibration is significantly worse when making a right turn; but barely noticeable, if at all, when making a left turn.

  • imidazol97imidazol97 Crossroads of America: I70 & I75Posts: 18,460

    @gifron said: High frequency, not matching tire rotations. Vibration occurs at all speeds, and in all gears. Plugs and wires probably need to be changed, but it does not seem to be an engine issue. I have run injector cleaner through in the not too distant past.

    Sounds like tires or hub bearing. Switch front tires left and right and see if the sensation switches with the tires and rims. While tire is up, check the right front hub for play in and out. Should be less than 0.05 in. Some people try rocking the bearing, top/bottom and left and right to feel play. Be careful not to have ball joint or tie rod play fool you. This has to be movement in the hub. Probably l/8 in max. Spin tire to see if you hear/feel any vibration. Compare left and right front for play.

    Then check rear bearings just for fun.

    I do not know how to check the half-shafts for play other than I could take hold of mine and get no play in the CV joint.

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