Weird engine shake

Hi,

I have a very strange engine shake. The engine idles ok, but sometimes the engine shakes terribly above RPM 1500. If I try to revolve the engine in neutral, it shakes so much, that I'm worried the engine will shake out of the car. The car is not driveable when this happens. I changed the spark plugs, cleaned the distributor, changed distributor cap and rotor. It seems they do not help.

I also noticed that the idle speed is a little bit high at 900 RPM. I can hear some noise from the timing chain cover area. I removed the upper timing chain guide, but it does not help.

Any ideal what's going on. Thanks.

I suggest checking your motor mounts. Mine are starting to go bad on my 2000 Altima (99,500 miles) and I do get a little bit of shaking at idle speed, but only while I'm in gear. There's 3 or 4 motor mounts, but the easiest one to get to is on the top left portion of the engine compartment. It's located right next to your power steering pump. To check if it's bad, you need a second person to put your vehicle in gear, apply the brakes and rev the engine slowly. As the engine revs while in gear, your motor will slowly rise at an angle, allowing the top motor mount to become stretched. If you see any kind of cracking or breaking in the material within the mount, you need to get it replaced. Chances are if one mount is going bad, the others are going bad as well. Good Luck! :wink:

Thank you very much for the reply. I think you are right, the motor mount might go bad. I will check it out as you mentioned. However, I still think there is some problem with the engine itself. I mean, if only the mount is broken, if the engine is smooth, it won't shake so badly when the car is in neutral, right?

Thanks.




I suggest checking your motor mounts. Mine are starting to go bad on my 2000 Altima (99,500 miles) and I do get a little bit of shaking at idle speed, but only while I'm in gear. There's 3 or 4 motor mounts, but the easiest one to get to is on the top left portion of the engine compartment. It's located right next to your power steering pump. To check if it's bad, you need a second person to put your vehicle in gear, apply the brakes and rev the engine slowly. As the engine revs while in gear, your motor will slowly rise at an angle, allowing the top motor mount to become stretched. If you see any kind of cracking or breaking in the material within the mount, you need to get it replaced. Chances are if one mount is going bad, the others are going bad as well. Good Luck! :wink:

I just checked the mount. They are pretty worn out. No wonder whenever I tried to engage the clutch, it gives a jerk. I thought I am a bad manual driver.

BTW, the car is a 96 Altima GXE with 170 K.

Thank Methodmix again for the suggestions.

Is changing the mount an easy DIY? Thanks.

Thank you very much for the reply. I think you are right, the motor mount might go bad. I will check it out as you mentioned. However, I still think there is some problem with the engine itself. I mean, if only the mount is broken, if the engine is smooth, it won't shake so badly when the car is in neutral, right?

Thanks.

Well, it depends on which mounts are screwed up... Also, you'll probably need a jack to support the jack or transmission (whatever is attached to the mount you're removing). Removing the mounts themselves is not complicated, but you'll definitely need a good deal of strength to get the bolt loose, and room to do it, too. From what I've heard, its not so simple on Nissans. Take a peak under the car, look for the cracked ones, its a matter of how accessible they are, IMO.

No prob. Glad you found the problem! Did you check all of the mounts or just the one at the top of the engine compartment? It sounds like the one that is attached to your transmission might also be going bad, which could explain the jerk you feel when you engage your clutch. My Altima is an automatic, but I do notice a significant jerk when I go from Park(neutral) to Drive(gear). I've also had my bottom mounts checked professionally, and they are also going bad.

As for DIY, the top mount should be the easiest to replace (i.e. easy to get to). I would support your engine with a hydraulic jack if you wish to replace any specific mount. I suggest getting a Haynes manual if you really aren't sure what to do.


I just checked the mount. They are pretty worn out. No wonder whenever I tried to engage the clutch, it gives a jerk. I thought I am a bad manual driver.

BTW, the car is a 96 Altima GXE with 170 K.

Thank Methodmix again for the suggestions.

Is changing the mount an easy DIY? Thanks.

That also sounds like a bad knock sensor, is throwing a CEL?

No, there is not check engine light. In tht case could it still be the knock sensor? Thanks.


That also sounds like a bad knock sensor, is throwing a CEL?

Well if it is still shaking and the CEL is not coming on,.......um......I would go with a tune up, plugs, wires, and 02 sensor for safety. A bad 02 Sensor will make your car drive just as bad as a bad knock sensor, but it would also throw the light on. Just trying to think of little things that can make a problem seem bigger than it really is.

Hi guys,

After I changed all the motor and transmission mounts, all the vibration is gone. It's like a miracle.

Thanks again for the advice.



No prob. Glad you found the problem! Did you check all of the mounts or just the one at the top of the engine compartment? It sounds like the one that is attached to your transmission might also be going bad, which could explain the jerk you feel when you engage your clutch. My Altima is an automatic, but I do notice a significant jerk when I go from Park(neutral) to Drive(gear). I've also had my bottom mounts checked professionally, and they are also going bad.

As for DIY, the top mount should be the easiest to replace (i.e. easy to get to). I would support your engine with a hydraulic jack if you wish to replace any specific mount. I suggest getting a Haynes manual if you really aren't sure what to do.

Excellent! So did you end up doing the work yourself or did you have it all done professionally? I haven't yet had my mounts replaced so I was just wondering what they would charge for labor.

I changed the transmission mount and the passenger side upper motor mount by myself, and had the other two motor mounts underneath changed by a mechanic.

I have a Mexican buddy, who run a garage. He charged me $25 each.

If you want to DIY, you need to first jack up the car and put the body on jack stand, then jack up the engine or transmission depending on which mount you want to change. Do not panic when you can not align the cross bolts through the mount and the bracket. Try jack up and down a little bit each time. When I changed my transmission mount, I end up loosing the bracket too.

If you do not have a deep offset 14 mm box wrench, buy it before you start to work on that.


Good luck.






Excellent! So did you end up doing the work yourself or did you have it all done professionally? I haven't yet had my mounts replaced so I was just wondering what they would charge for labor.

Cool, thanks for the suggestions. I will be acquiring a free 1-ton hydraulic jack pretty soon, so that'll be when I attempt the job. Cheers!


I changed the transmission mount and the passenger side upper motor mount by myself, and had the other two motor mounts underneath changed by a mechanic.

I have a Mexican buddy, who run a garage. He charged me $25 each.

If you want to DIY, you need to first jack up the car and put the body on jack stand, then jack up the engine or transmission depending on which mount you want to change. Do not panic when you can not align the cross bolts through the mount and the bracket. Try jack up and down a little bit each time. When I changed my transmission mount, I end up loosing the bracket too.

If you do not have a deep offset 14 mm box wrench, buy it before you start to work on that.


Good luck.

Yeah if your bolts don't line up, loosening brackets always works. just remember to tighten them back up.