bad vibration coming from rear of car ¿fuel pump?

[1994Vib.RedGT]

ok, today I noticed a horrible vibration coming from the back of my car, it sounded like when you hear a subwoofer rattle someones license plate, except it was rattling my whole car!! and it does it anytime I am in the gas, or the rpms are higher than idle, before you say a.check the license plate" or b.turn the stereo off, the license plate was tight, and the stereo was off, so that is not it. I then decided to put the rear seats down and listen for it, sure enough it is coming from somewhere under the trunk. my first thought was that my tailpipe was rubbing the axle, but it was not, so then I was thinking, maybe the fuel pump has gone bad????? please help me.

 

[1994Vib.RedGT]

bump

 

[CManT1914]

I don't think a faulty fuel pump would cause bad vibrations. You're sure your exhaust cleared the driveshaft too? My pass. side muffler was rubbing the driveshaft and causing a bad vibration. Might want to check out your sway bar too, those have been known to snap and cause rattles and stuff. Mine did, and the back of my car was squeak/rattle/vibration kingdom.

 

[urban96]

try crawling under there and bang on things with your hand to see if you can reproduce the sound. i dont see how the fuel pump could cause it, usually they just wine.... loudly..

is your car auto or manual? i also see you have gears, did it do that before the gears too?

 

[1994Vib.RedGT]

i have gears, but they have been in there since ~1998, so that is not the problem. this rattle just started the other day. I checked to see if the jack in the tire well was tight, and yea, its tight, i cannot for the life of me figure it out, i went to my dads today and he said it sounds like maybe the muffler is old and there is a piece clanging around in there, my flowmasters have been on the car since 1996, so its possible, but it dosent sound like that.or the muffler rubbing against the driveshaft, as someone else previously suggested, but i would prefer not to go under my car while it is running. it is irritating the chit out of me!!!!

 

[1994Vib.RedGT]

I don't think a faulty fuel pump would cause bad vibrations. You're sure your exhaust cleared the driveshaft too? My pass. side muffler was rubbing the driveshaft and causing a bad vibration. Might want to check out your sway bar too, those have been known to snap and cause rattles and stuff. Mine did, and the back of my car was squeak/rattle/vibration kingdom.

the sway bar looks ok, and wouldnt there be a noticable difference in handling, etc. if the swaybar was busted?

 

[CManT1914]

the sway bar looks ok, and wouldnt there be a noticable difference in handling, etc. if the swaybar was busted?

Yes, the rear would feel looser in the corners. When I mentioned checking to see if the muffler is rubbing, you don't have to have the car running. Even if it is running the d/s isn't spinning unless the car is moving, and if you're under the car while it's moving, you have bigger problems than a rubbing muffler. But you should be able to see the muffler butted up against the d/s, and on mine, there was a perfect 1/2" streak of bare metal where the muffler had worn off the rust (or whatever that red crap all over the d/s is).

 

[mo_dingo]

The fuel pump makes a whining, and it's completely normal.

Ok, let me get this straight. When you are sitting still, not driving, the car vibrates in the rear?

Or is it in only in motion?
Scott

 

[SeventyMach1]

Question 4 U: When you are in the car, while it is running.... but not "moving".....and you give it some gas (above idle as you're saying), does it do it then?

 

[urban96]

sounds like it could be something inside the muffler

 

[SeventyMach1]

sounds like it could be something inside the muffler

Yeah, maybe a chunk of the cat..... or do you still have a cat, lol.

 

[HISSIN50]

If not mentioned, dont forget to check the junk in the spare tire well. tools and stuff down there can rattle around and create a lot of noise.

Good luck.

 

[1994Vib.RedGT]

Question 4 U: When you are in the car, while it is running.... but not "moving".....and you give it some gas (above idle as you're saying), does it do it then?

yes it does, if i am sitting still at idle, no vibration, but if i rev the motor, it vibrates, and no i have no cats.

 

[1994Vib.RedGT]

If not mentioned, dont forget to check the junk in the spare tire well. tools and stuff down there can rattle around and create a lot of noise.

Good luck.

checked that, nothing there, spare tire and all are tight

 

[1994Vib.RedGT]

i was thinking, the driveshaft does not turn when the car is idleing correct, or if you rev the motor from an idle???? if it dosent then that would rule out the driveshaft rub correct?

 

[HISSIN50]

i was thinking, the driveshaft does not turn when the car is idleing correct, or if you rev the motor from an idle???? if it dosent then that would rule out the driveshaft rub correct?

the driveshaft does not turn while the car is stationary. You can be idling while rolling in gear or neutral, which will make the DS turn.

On the 88, when I had the pass side exhaust close to the frame rails (to get it away from the driveshaft), it would make a metallic noise and rumble through the car as it bounced off the frame rail with each cadence. When you rev the motor, the harmonics change - that could do it.

Good luck.

 

[slytherin]

What about the harmonic balancer, the motor is bolted to the chassis and transmitting throught the whole car.

 

[SeventyMach1]

Well ,the driveline is now eliminated. Put car in park/neutral. Set the brake. Have someone else sit in the car & give it some gas. You go behind the car/under the rear bumper & check it out to try & see exactly "where" the noise is coming from. If the mufflers/tailpipes aren't rubbing and nothing else is loose, like the jacking equipment, you may want to check into the fuel pump.

Does it make the "normal" whine when you turn the key to "on"? Is the fuel pressure reading normal?

 

[1994Vib.RedGT]

yea, fuel pump makes the normal whine, i checked and the tailpipes or mufflers are not hitting the drivshaft or anything else. my dad seems to think that this has nothing to do with fuel pump though, he thinks something inside the muffler, but it is not so much a metallic clanking as much as a rough vibration that sounds like the license plate when it rattles if you have a stereo. is it passible that it could be something in the differential, or where the driveshaft enters the differential?

 

[94-302-vert]

I Think inside the muffler...

Back the car onto some ramps or use some jackstanda and do the running with you listening from next to the car (preferable not under the car)...