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99 cobra shakes durring acceleration

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Old 11-06-2013, 09:07 PM   #1
djcondo
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Default 99 cobra shakes durring acceleration

Hey all,
Just got a 99 cobra and i notice that it shakes a little under acceleration. If i rev the car there is no vibration whatsoever but when i am back in gear and accelerating it shakes. I have already checked the driveshaft u joints and they seem fine and have found and replaced one cross axis joint. The car has 165k on it..

Also there is a slight clunk in the front end somewhere when hitting the brakes hard or it is sometimes heard when turning

Let me know please, I am new to the cobra world
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Old 11-09-2013, 03:25 AM   #2
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There are a lot of things to check, my money is on a motor mount, especially with 165k. Check the motor mounts, the transmission mount, possibly a wheel bearing, possibly the other CV shaft.
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Old 11-11-2013, 06:42 PM   #3
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Ok so I found out what the clunk was but still have the driveline vib. The bell housing was coming into contact with the K member brace. I threw a washer on the brace and no more clunk but still a vim under harder accel. The trans mount seems real tight i can not move the tail of the trans
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Old 11-11-2013, 10:21 PM   #4
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Ok so I found out what the clunk was but still have the driveline vib. The bell housing was coming into contact with the K member brace. I threw a washer on the brace and no more clunk but still a vim under harder accel. The trans mount seems real tight i can not move the tail of the trans
I'm absolutely certain it's the motor mount now. If it's hitting that brace, then the mount is broken and needs to be replaced.
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Old 11-12-2013, 06:18 PM   #5
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how much space should be between the two?
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Old 11-13-2013, 12:37 AM   #6
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how much space should be between the two?
I have no idea, but I do know that the bellhousing isn't supposed to touch. Shaking during acceleration + the bellhousing hitting that brace = busted motor mount. There is no question about it. Put a jack under the oil pan, with a block of wood to spread out the pressure and lift it up. If the mounts are good then the engine wont go up.
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Old 11-13-2013, 09:00 AM   #7
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I'd also suggest taking a real good look at the IRS mounts and everything out back, as these things get old they're going to run into more issues with worn out IRS mounts and shafts.

Last edited by Steve@Tasca; 11-13-2013 at 09:10 AM.
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Old 11-18-2013, 07:24 PM   #8
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Well threw in some motor mounts and that solved the driveline vibe. They are so trashed that the oil pan was touching the steering rack. I have seen some junk motor mounts but never this bad. One side had half the rubber gone and when I popped it out chunks of rubber was falling out.

On a side note. I now notice a slight miss/ stumble/ shake in rpm between idle and about 3000 ish. I don't feel it really when driving but when reving I feel it. Time to figure that one out. Let me know if you smart fellows know what to check with that.
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Old 11-19-2013, 08:57 AM   #9
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Maybe try getting the real wheels safely and solidly off the ground and then run it through the gears and see if it does it with the car off the ground.
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Old 11-19-2013, 09:13 AM   #10
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Well it seems like engine running rough not anything related to driveline and spinning. I was going to just pull one plug wire off at idle and see if any one does not make a difference to check my spark/ ignition system
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Old 11-19-2013, 10:52 AM   #11
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Well it seems like engine running rough not anything related to driveline and spinning. I was going to just pull one plug wire off at idle and see if any one does not make a difference to check my spark/ ignition system
I missed where you said it did it when revving.

Plugs, wires and coils would be a good place to start.

-Steve
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Old 11-19-2013, 02:17 PM   #12
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Ok thanks. Just checking to make sure my thought process is correct
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Old 11-19-2013, 07:43 PM   #13
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Just let it idle and pulled one coil off at a time. All rpm dropped evenly. I'm going to change out my spark plugs since the mileage is so high. Anyone have a recommended spark plug? I hear these heads have an issue with blowing out spark plugs
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Old 11-19-2013, 07:47 PM   #14
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Just let it idle and pulled one coil off at a time. All rpm dropped evenly. I'm going to change out my spark plugs since the mileage is so high. Anyone have a recommended spark plug? I hear these heads have an issue with blowing out spark plugs
Just make sure to warm the engine up a good bit before you take the plugs out and put anti seize on them when they go back.
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Old 11-27-2013, 03:23 PM   #15
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hey its gonna be your ignition coil i just had same issue on my 2001 gt sputtering when i got on the gas hard long as i eased on the gas i was good then other times it would do it in that case to but about 100% sure same issue with yours to bro when i pulled out old coil the boot was seperated from the main coil already thus mis fireing
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Old 11-27-2013, 03:23 PM
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