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Low Rpm Internal Vibration Noise

by kbrews, October 24, 2007



I have a 1994 Prizm, 4A-FE engine. 107k miles. As I mentioned in a post awhile back I recently took it in for the timing belt change (overdue preventative maintenance) and asked the mechanic to also see about a vibration noise I was getting at idle. I thought it would just be the heat shield or something loose in the exhaust. Anyway he found two motor mounts were bad and replaced them. This solved the problem. Situation resolved -- I thought.

However, gradually the vibration noise came back, now 6 months later. This time I have the same guy look at it and he can't find anything, he took it to a nearby muffler shop and they couldn't find anything loose. He said he could replace the other two mounts and it would cost about $300-something for parts plus labor, but he honestly thought that were just fine as-is. So I took it to the Chevy dealer thiinking they might have more direct experience with the Prizm. The mechanic there did several tests including removing all the belts, etc, and determined that the noise had to be coming from within the engine itself or the transmission. He said he would not be able to tell for sure without tearing into the engine. He could only guess about a bent rod or camshaft or warped flywheel. Of course opening the engine and reclosing it will be big dollars labor. He said another mechanic in the dealership owns a Prizm that has a similar noise and he has just lived with it.

This noise is there at high idle speeds, but goes away at higher RPM, and there does not seem to be any effect on performance. Its there also if I am driving at 5-10 mph, such as driving in a parking lot. It is there in neutral and 1st gear (5 speed manual). It can be fairly loud and varies somewhat with outdoor and engine temperature. Since the noise is there in manual and 1st gear, I suspect its not the transmission (?). It seems to me if there was a bent rod or camshaft the vibration would be worse at high RPM.

Has anyone else run into this and what did you do to resolve it? If I just live with it, I suppose the engine could still last a many thousand miles, yet, as I had hoped. We were planning to replace my wife's car (150+k miles) first, soon, and continue driving this one for a couple years, yet -- cosmetically and otherwise mechanically its in great condition. I'm not one to rebuild an engine myself, so I think the cost of that is prohibitive compared to the street value of the car. Maybe I need a louder stereo.

I doubt the issue is the tranny or engine, unless you can think offhand if there was any event that could have potentially caused any problems with them. The 4AFE and C50/52 transmission are known to be a very tough, reliable combination. Since the problem seemed to have been solved with new engine mounts and it gradually came back - might be a resonance issue with the engine itself. Did the mechanic check the timing of the engine - just to rule out wrong timing? Did he try prying on the engine mount to see if the vibration changed at all? Sometimes you can jack up th front corner of the car to see if the engine/transmission mounts are having anything to do with the noise. CV joint slop, powersteering pump groan, and a loose exhaust system can cause vibrations. If you haven't noticed any drivability issues (fuel economy, idle quality, engine power, etc.) - just keep going and see if the noise evolves (gets better or worse), as it is ometimes easier to pinpoint vibrations if the part wears out more. But don't wait too long. Good Luck.

Bikeman982

Just how loud does the noise get?

Is it so loud that a better stereo would have trouble drowning it out?

Is it really an engine related noise, and not a CV joint, driveshaft, engine mount, or hub and bearing problem?

I have the 4A-FE engine on my project car and have been trying to eliminate all bad noises.

I have changed the transaxle and also the driveshafts and maybe next will be the mounts.

The tranny shop wanted to change the front hub and bearings due to a noise in the front end.

I am still working on it.

More to follow.

Hard to say on a problem like this without hearing it first hand. Strange that it went away and then came back but it could be something else not related to the engine mount swap.

If you can duplicate the problem in neutral sitting still at a certain RPM have someone sit in the car with the RPM where the noise occurs and slowly lift the engine with a floor jack. If the noise goes away it is related to mounts or possibly exhaust hangers etc.

The previous replies covered many things and I don't think it will be IN your engine. Has anyone listened to the bellhousing area....possibly related to clutch_throwout bearing_pilot bushing functionality??

Good luck,

Jay in MA

I have a 1994 Prizm, 4A-FE engine. 107k miles. As I mentioned in a post awhile back I recently took it in for the timing belt change (overdue preventative maintenance) and asked the mechanic to also see about a vibration noise I was getting at idle. I thought it would just be the heat shield or something loose in the exhaust. Anyway he found two motor mounts were bad and replaced them. This solved the problem. Situation resolved -- I thought.

However, gradually the vibration noise came back, now 6 months later. This time I have the same guy look at it and he can't find anything, he took it to a nearby muffler shop and they couldn't find anything loose. He said he could replace the other two mounts and it would cost about $300-something for parts plus labor, but he honestly thought that were just fine as-is. So I took it to the Chevy dealer thiinking they might have more direct experience with the Prizm. The mechanic there did several tests including removing all the belts, etc, and determined that the noise had to be coming from within the engine itself or the transmission. He said he would not be able to tell for sure without tearing into the engine. He could only guess about a bent rod or camshaft or warped flywheel. Of course opening the engine and reclosing it will be big dollars labor. He said another mechanic in the dealership owns a Prizm that has a similar noise and he has just lived with it.

This noise is there at high idle speeds, but goes away at higher RPM, and there does not seem to be any effect on performance. Its there also if I am driving at 5-10 mph, such as driving in a parking lot. It is there in neutral and 1st gear (5 speed manual). It can be fairly loud and varies somewhat with outdoor and engine temperature. Since the noise is there in manual and 1st gear, I suspect its not the transmission (?). It seems to me if there was a bent rod or camshaft the vibration would be worse at high RPM.

Has anyone else run into this and what did you do to resolve it? If I just live with it, I suppose the engine could still last a many thousand miles, yet, as I had hoped. We were planning to replace my wife's car (150+k miles) first, soon, and continue driving this one for a couple years, yet -- cosmetically and otherwise mechanically its in great condition. I'm not one to rebuild an engine myself, so I think the cost of that is prohibitive compared to the street value of the car. Maybe I need a louder stereo.

I have a 1995 Geo Prizm, 1.8L, AT and ~92K miles that sounds like it has a very similar problem. I recently purchased the car and this vibration is that last thing I need to fix. I test drove a Corolla that had a very similar vibration issue and believe that there is a remedy (though I don't yet know what it is). Please let me know if you solve your vibration problem and I will do likewise. I have been through most of the checks in the service manual and have yet to solve the problem.

Bikeman982

Vibration that occurs when the car is just idling can be many things.

Maybe it is timing slightly off, bad motor mounts, an out of balance pulley, something loose in the engine, etc.

Bent rods or camshafts tend to smooth out at faster engine speeds.

Unless it is extremely bad vibration or causes the engine to run excessively rough, I would not be overly concerned.

I would wait to see if it gets worse over time or remains the same.

Vibration that occurs when the car is just idling can be many things.Maybe it is timing slightly off, bad motor mounts, an out of balance pulley, something loose in the engine, etc.

 

Bent rods or camshafts tend to smooth out at faster engine speeds.

Unless it is extremely bad vibration or causes the engine to run excessively rough, I would not be overly concerned.

I would wait to see if it gets worse over time or remains the same.

In my case; I have checked the timing and 3 of the 4 mounts (replaced one) and all is well (I still need to crawl under the car to check the fourth mount but I don't believe that will solve my problem). I briefly ran the car without the alternator, water pump and power steering pump belt and the vibration was still there.

Bent rods or camshafts sound pretty serious--is that a common problem? And how could either occur? At this point I don't believe that it is internal to the engine unless you can convince me otherwise--I have had a few brief moments were the car was running well but I haven't been able to pinpoint why.

The thermostat was stuck open when I purchased the car so it had been running too cold for some time--I wonder if this could have fouled the intake and the injectors and ???? and be causing my problem.

In my case; I have checked the timing and 3 of the 4 mounts (replaced one) and all is well (I still need to crawl under the car to check the fourth mount but I don't believe that will solve my problem). I briefly ran the car without the alternator, water pump and power steering pump belt and the vibration was still there.

Bent rods or camshafts sound pretty serious--is that a common problem? And how could either occur? At this point I don't believe that it is internal to the engine unless you can convince me otherwise--I have had a few brief moments were the car was running well but I haven't been able to pinpoint why.

The thermostat was stuck open when I purchased the car so it had been running too cold for some time--I wonder if this could have fouled the intake and the injectors and ???? and be causing my problem.

Interesting that you mention the stuck thermostat, because that was the same with my car. I didn't even notice it, but with the timing belt change he installed new water pump and thermostat and I found the car was warming up a lot faster.

So far no changes to the noise, I might just live with it for awhile, and poke around a bit myself someday. If I ever have it serviced again, I might just go ahead and have those other two motor mounts changed. If nothing else the new rubber vs 14 year old rubber should change the resonant frequency a bit. That, and some settlling-in may have been what happened the first time I thought this was resolved.

Meanwhile I may starting looking for a low-miles lease return Corolla or Camry to show up on a nearby dealer's online inventory.

Bikeman982

In my case; I have checked the timing and 3 of the 4 mounts (replaced one) and all is well (I still need to crawl under the car to check the fourth mount but I don't believe that will solve my problem). I briefly ran the car without the alternator, water pump and power steering pump belt and the vibration was still there.

Bent rods or camshafts sound pretty serious--is that a common problem? And how could either occur? At this point I don't believe that it is internal to the engine unless you can convince me otherwise--I have had a few brief moments were the car was running well but I haven't been able to pinpoint why.

The thermostat was stuck open when I purchased the car so it had been running too cold for some time--I wonder if this could have fouled the intake and the injectors and ???? and be causing my problem.

Interesting that you mention the stuck thermostat, because that was the same with my car. I didn't even notice it, but with the timing belt change he installed new water pump and thermostat and I found the car was warming up a lot faster.

So far no changes to the noise, I might just live with it for awhile, and poke around a bit myself someday. If I ever have it serviced again, I might just go ahead and have those other two motor mounts changed. If nothing else the new rubber vs 14 year old rubber should change the resonant frequency a bit. That, and some settlling-in may have been what happened the first time I thought this was resolved.

Meanwhile I may starting looking for a low-miles lease return Corolla or Camry to show up on a nearby dealer's online inventory.

Check out the Corollas. Even with high mileage, they are a good car.

 

 

In my case; I have checked the timing and 3 of the 4 mounts (replaced one) and all is well (I still need to crawl under the car to check the fourth mount but I don't believe that will solve my problem). I briefly ran the car without the alternator, water pump and power steering pump belt and the vibration was still there.

Bent rods or camshafts sound pretty serious--is that a common problem? And how could either occur? At this point I don't believe that it is internal to the engine unless you can convince me otherwise--I have had a few brief moments were the car was running well but I haven't been able to pinpoint why.

The thermostat was stuck open when I purchased the car so it had been running too cold for some time--I wonder if this could have fouled the intake and the injectors and ???? and be causing my problem.

Interesting that you mention the stuck thermostat, because that was the same with my car. I didn't even notice it, but with the timing belt change he installed new water pump and thermostat and I found the car was warming up a lot faster.

So far no changes to the noise, I might just live with it for awhile, and poke around a bit myself someday. If I ever have it serviced again, I might just go ahead and have those other two motor mounts changed. If nothing else the new rubber vs 14 year old rubber should change the resonant frequency a bit. That, and some settlling-in may have been what happened the first time I thought this was resolved.

Meanwhile I may starting looking for a low-miles lease return Corolla or Camry to show up on a nearby dealer's online inventory.

I am still working on tracking down the souce of my vibration and am running out of options. Yesterday I checked the compression which was fine and last weekend I replaced the rear motor mount which was totally shot. I have replaced both the front and rear mounts but am thinking they may have failed because of this vibration. The vibration is still there with the new mounts. I have spent so much time trying to track down (I won't begin to list everything I have checked) this problem that I am not about to give up yet especially since everything is telling me that the motor is mechanically sound. I can't believe someone else with a similar problem can't direct us to a possible solution. If I do solve my vibration problem, I will be sure to post it here with the hope that it helps you. Good luck.

Bikeman982

People with similar problems don't always have similar solutions.

There are multiple causes (such as mounts) that can cause your problem.

Keep working on it and tell us what you find.

Guest gotmolo

Add me to the list of people with the EXACT vibration issue discussed here in this thread. I have 88,000 miles on my 93 corolla (1.8L w/auto). I bought it last year with 74,000 miles, and after taking ownership, I changed all the belts, fluids, plugs, wires, air filter, gas filter, trans filter, and all 4 struts (the struts where ALL blown). I also replace the thermostat, which was stuck open as well!! I was still getting the same vibration everyone talks about (the entire cabin resonates). I decided that, since it probably haden't been changed, I'd replace the timing belt. I was right; it was super cracked and ready to go. I followed the corolla service manual exactly, and when I was ready to remove the old belt, I noticed that I could not line up the sight marks on the cam gear and crank gear simutaneously. When one was in the correct position, the other was slightly off.

My guess is the belt had jumped a couple teeth. Is this common? To correct this, I rotated the crankshaft ( I think counterclockwise) ever so slightly, where the mark on the gear lined up.

To my suprise, the vibration seemed to decrease a little. BUT it is still there.

Also, when I stand in front of my car when it's running, I can hear something resonating from the passenger side fender. The car has some scraps on the bumper from the previous owner, and when I crawled under there, I noticed the fender was vibrating at the point of contact, where it mounts to the engine bay. If I stand right next corner of the bumper at that point and apply pressure with my leg, the noise stops, but the vibration is still there.

I think the fender compounds problem. I need to find whatever is causing the vibration.

As far as engine mounts go, I had a 91 jeep wranger in highschool that had a busted engine mount. I knew this because I could FEEL the engine moving around. I didn'tt recall any vibration. That's why it's hard for me to believe the mounts on my corolla are bad. I'm going to try jacking up the motor while it's running and seeing if that changes anything.

Just to clarify, this is only noticeable at idle. It does seem to get better as the engine warms up. I gotta change the oil this saturday, so I'm going to get under the car and inspect the mounts. I'll try to take some pictures too.

These cars do vibrate quite a bit. My 95 is at 218K miles and I'm sure it could benefit from new mounts. Try the floor jack method as I described above. The vibration will probably go away when you take some of the weight off of the mounts.

Mounts can also be affected by ozone and ozone levels differ from one area to the next. It also affects the longevity of timing belts etc.

Jay in MA

Add me to the list of people with the EXACT vibration issue discussed here in this thread. I have 88,000 miles on my 93 corolla (1.8L w/auto). I bought it last year with 74,000 miles, and after taking ownership, I changed all the belts, fluids, plugs, wires, air filter, gas filter, trans filter, and all 4 struts (the struts where ALL blown). I also replace the thermostat, which was stuck open as well!! I was still getting the same vibration everyone talks about (the entire cabin resonates). I decided that, since it probably haden't been changed, I'd replace the timing belt. I was right; it was super cracked and ready to go. I followed the corolla service manual exactly, and when I was ready to remove the old belt, I noticed that I could not line up the sight marks on the cam gear and crank gear simutaneously. When one was in the correct position, the other was slightly off.

My guess is the belt had jumped a couple teeth. Is this common? To correct this, I rotated the crankshaft ( I think counterclockwise) ever so slightly, where the mark on the gear lined up.

To my suprise, the vibration seemed to decrease a little. BUT it is still there.

Also, when I stand in front of my car when it's running, I can hear something resonating from the passenger side fender. The car has some scraps on the bumper from the previous owner, and when I crawled under there, I noticed the fender was vibrating at the point of contact, where it mounts to the engine bay. If I stand right next corner of the bumper at that point and apply pressure with my leg, the noise stops, but the vibration is still there.

I think the fender compounds problem. I need to find whatever is causing the vibration.

As far as engine mounts go, I had a 91 jeep wranger in highschool that had a busted engine mount. I knew this because I could FEEL the engine moving around. I didn'tt recall any vibration. That's why it's hard for me to believe the mounts on my corolla are bad. I'm going to try jacking up the motor while it's running and seeing if that changes anything.

Just to clarify, this is only noticeable at idle. It does seem to get better as the engine warms up. I gotta change the oil this saturday, so I'm going to get under the car and inspect the mounts. I'll try to take some pictures too.

This reminds me of excessive vibration at idle in my '93 back maybe 6 or 7 years ago. Not sure what the mileage was.

I decided it could be an engine mount, but then it ceased before I took any action on it.

I can't recall any repairs that would have affected it.

Bikeman982

Engines are supposed to be balanced at the factory, but after some time and many miles, they become worn.

Engine mounts do go bad, but not all at the same time.

Timing can be a big factor on how the car runs as well as affect the engine vibrations.

Keep looking and eventually you will find the cause of your vibrations.

1993-1997 toy corollas are known to be "vibrators". you just learn to live with it, nothing wrong with your car

I have to agree. Just seems to be the nature of the beast. That's why I find it so hard to identify front axle problems.

Jay in MA

1993-1997 toy corollas are known to be "vibrators". you just learn to live with it, nothing wrong with your car
I have to agree. Just seems to be the nature of the beast. That's why I find it so hard to identify front axle problems.

Jay in MA

1993-1997 toy corollas are known to be "vibrators". you just learn to live with it, nothing wrong with your car

 

Some updates on my '94 Prizm. There is still some vibration, but as others have mentioned it is not severe and doesn't seem to affect performance. I did discover a couple things that are causing the NOISE from the vibration which is what was bothering me. 1) the right rear view mirror housing had been cracked and I found that the plastic was vibrating a bit along the crack causing a buzz at certain RPMs. I had tried to fix it with epoxy, but it did not work well nor look good so I just replaced that. 2) another trim item that was creating the loudest noise was the bumper cover -- it was slightly loose and the top edge was vibrating against the body at idle. I tightened up the bolts near the front wheel wells on both sides. This resolved the loudest noise that was occurring. When we get a warm weekend I plan to loosen them a bit and put a bead of clear silicone caulk along that joint and tighten again. Then if it ever works loose again it won't be free to buzz.

Bikeman982

I have to agree. Just seems to be the nature of the beast. That's why I find it so hard to identify front axle problems.

Jay in MA

1993-1997 toy corollas are known to be "vibrators". you just learn to live with it, nothing wrong with your car

 

Some updates on my '94 Prizm. There is still some vibration, but as others have mentioned it is not severe and doesn't seem to affect performance. I did discover a couple things that are causing the NOISE from the vibration which is what was bothering me. 1) the right rear view mirror housing had been cracked and I found that the plastic was vibrating a bit along the crack causing a buzz at certain RPMs. I had tried to fix it with epoxy, but it did not work well nor look good so I just replaced that. 2) another trim item that was creating the loudest noise was the bumper cover -- it was slightly loose and the top edge was vibrating against the body at idle. I tightened up the bolts near the front wheel wells on both sides. This resolved the loudest noise that was occurring. When we get a warm weekend I plan to loosen them a bit and put a bead of clear silicone caulk along that joint and tighten again. Then if it ever works loose again it won't be free to buzz.

It seems that if anything is loose or cracked, it will vibrate. Add enough of these vibrating areas and the car will be too loud.

 

It is good that you have isolated some of the worst noise areas and hopefully you will find them all.

Yup...same with my 95.....that thing is noisey.

..........another trim item that was creating the loudest noise was the bumper cover -- it was slightly loose and the top edge was vibrating against the body at idle. I tightened up the bolts near the front wheel wells on both sides. This resolved the loudest noise that was occurring. When we get a warm weekend I plan to loosen them a bit and put a bead of clear silicone caulk along that joint and tighten again. Then if it ever works loose again it won't be free to buzz.

Bikeman982

Add noise and vibration to the car which has very little sound deadoning material and it can get loud.

There is very little material between the road/outside world and the inside of the car.

If I were to make a car for myself, I would pad all doors and floor as well as the front and back areas.



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