Vibration at idle (and a little above)

Hi all. I posted a thread similar to this before, but I wanted to be more specific. My 2009 Pontiac Vibe GT (Toyota 2.4l 2AZ FE engine) has had a rather intense vibration between 700-1000 rpm ever since the engine was rebuilt (oil burning pistons replaced) over 8 months ago. The vibration did not exist in this quality or quantity before the rebuild. The vibration is noticeable around 700 rpm and gradually intensifies as rpms increase to about 1000, then smooths out past that (actually still kind of rough, but it doesn’t bother me and is more like a buzzing than a shaking-I suppose because the rpms are so fast at that point.) The vibration exists hot or cold, in and out of gear, accessories on or off, and can be felt in the seat, pedals, frame, everywhere. The steering wheel and rear view mirror visibly shake. The car also jerks/shakes when started. I should add that the catalytic converter was replaced as well, so the exhaust had been removed/re-installed.
Two key things I noticed right after the rebuild:
1.When I first drove the car, the vibration was almost unbearable. You would think a newly rebuilt engine would be smoother or, at least no worse than before. The mounts were all in need of replacement, but they were the same mounts I had before the rebuild, so that shouldn’t have mattered. I replaced them all with OEM mounts, which made a significant improvement, but something was still obviously wrong. The vibration is much more substantial than what would be expected of an older high-mileage four banger.
2. The car was noticeably louder than before. The sound was similar to that of a motorcycle or a car with the muffler removed, but not quite as loud. It has since quieted down or I’ve just gotten used to it or maybe both. About a month later,I noticed a fairly loud metallic rattle coming from under the car. I’m not sure exactly what it was because he didn’t tell me, but my brother in law (same guy who did the rebuild) fixed it and just said one of the bolts was stripped. I’m guessing a hanger or heat shield, but it was certainly an exhaust-related component. I don’t think this made any difference in the vibration, but the noise did go away.
I’ve addressed all the usual suspects for “vibration at idle.” I replaced the plugs, cleaned the throttle body, cleaned the fuel injectors (fuel trims are close to perfect) and there are no codes or even any slight abnormalities according to my OBD reader. I’m leaning toward the balance shafts or something to do with the exhaust, but these are just guesses and I really want to diagnose this before I take the car apart and/or throw any money at it.
Any ideas or advice are appreciated.
Thanks in advance,

I would guess the balance shafts were mis-timed. They need to be jn the correct position, much like camshafts to smooth out the vibration.

1 Like

Rechecking balance shafts is labor. Is your BIL a pro? Have a shop? Did you pay him?

You’re probably right. I’m just dreading fixing them.

No to all three questions.

A few things that made me doubt the balance shafts:

  1. When I replaced the last of four mounts (top passenger side) the was NO vibration at all for about an hour, then it gradually came back just as it was.
  2. It’s inconsistent. Sometimes the vibration isn’t as bad or I don’t feel it as much. The vibration will be more or less noticeable at the same RPMs. Although, the car doesn’t idle at exactly the same RPM all the time, so it could just be idling lower sometimes. The car idles around 650 with no accessories on and I can’t feel a thing, but as I take off/slow down I still feel the “rough patch” from 700-1000.
  3. There is also a “jerk” followed by a split-second shake (sometimes violent) when I start the car that varies in intensity at various startups (oddly, least prominent on cold start in the morning.) There is always a little jolt, but right after I replaced all the mounts, the startup was stunningly uneventful. It took me a second to acknowledge the car was running.
    Could these things be attributed to or rule out misaligned balance shafts?

What would I do if I were in your shoes?
First; connect a vacuum gauge to see if there is a mechanical fault involving compression. New top end should be around 20" of vacuum at idle with a steady needle.

If not, then a compression test. A dropped cylinder can cause vibration at idle/lower RPM which may subside as the RPMs go up. New top end should be in the 180 or higher range.


I’m almost positive the top end was not rebuilt and only the pistons were replaced (and catalytic converter.) Maybe the new pistons sealed much better and the added compression revealed a problem somewhere else in the engine? I have not done a vacuum gauge test, but I did do a cylinder compression test. I did the test about two hours after the engine had been off. Cylinder 1 read 185 psi and cylinders 2-4 read ~ 175. Specs for this engine are 196 psi max and 14 psi max difference between pistons. When I checked the plugs after 10k miles, one of them had a fair bit of white buildup, but I don’t remember which one. The other 3 looked good.

Your AC compressor is off during all this, right? Not saying you are dumb, but we all miss the simple things at times.

Haha :slight_smile: AC is usually on lately, but it doesn’t make any difference. The engine idles lower with the AC off, but the vibration is still there (700-1000 rpm) When I start the car in the morning, it idles up and gradually goes down as is normal. As it drops to 1000 rpm, the intense vibrations begin (they resonate like a subwoofer) and they gradually decrease as the rpms die down.

Compression is acceptable; but the use of a vacuum gauge might reveal something as far as vacuum leaks, weak valve spring, and so on.
Idle speed too low could cause a vibration but that should go away with a little throttle. A misfiring spark plug could also cause this and the one with the white deposits might be questionable.

Depending upon the appearance, a white tip could mean deposits from burning oil, overheated spark plug, or even engine coolant.

When it comes to replacing pistons/rings without cylinder inspection or boring any kind of situation can crop up; especially depending upon if a cylinder has an abnormal amount of egg or taper in it. Round rings in an oblong hole often does not work well and the outer limits on those specs is not very much.
For what it’s worth it’s easily possible to have 190 of compression and still have oil get past the rings.
Who did the top end? Just wondering.

My brother in law did all the work. I don’t know if he “did” the top end at all. As far as I know, he just replaced the pistons per the Toyota TSB and the catalytic converter because it was oil fouled. Wouldn’t my fuel trims be out of wack if I had a vacuum leak? My code reader shows no misfires. My oil consumption is greatly improved, but I still lose about a quart in 3000 miles. Does any of this have to do with intense engine vibration? It’s strange because I’ve experienced vibration due to worn mounts that went away in neutral, but this vibration between 700-1000 rpm (most intense around 950) is just something this engine does now regardless of condition.

just a thought… could the rubber in the harmonic balancer be beginning to fail?

1 Like

No, because this engine doesn’t have one. The engine is supposedly internally balanced and has balance shafts right under the no. 1 cylinder. The crank pulley just drives the belt accessories. Good guess, though. Something may be out of balance which is why I was leaning toward the balance shafts, but I want to rule out as many possibilities before I attempt that bear of a job.

I say this with all due sympathy and a sad shake of the head, but if your brother in law changed the pistons and rings without a re-bore of the cylinders or even honing them, he really doesn’t know his anus from his ulna. Nevertheless, you need to check the balance shafts.

This is not a soft iron block from the 1960’s, the cylinder walls do not wear prematurely. Rebore is not possible with the pistons listed in the service bulletin, they are for standard bore. Instructions below;

SB-10096245-5448.pdf (

1 Like

We’re going in circles here. Did you ever try to get the alignment of the engine as mounted completely correct, as you discussed in your first thread? With the way the mounts were reused and then replaced it seems at least likely that there is an issue there. I don’t understand how the balance shafts are driven (by the timing chain or directly geared to the crankshaft or the cams), but it seems like the mount question is less complex to attack and perhaps less expensive to clear up.

1 Like

The balance shafts are gear driven, no chain. I was able to see a picture of someone else’s Vibe and that one mount looked just like mine. I was also finally able to get it to line up straight too. There is quite a bit of play in one of the holes and I was installing the bolts in the wrong order according to the repair manual. I also chatted with another vibe owner who had the exact same symptoms I do. He replaced all the mounts and the car was perfect, but then started vibrating again in about a month. He also said the vibration was worst around 850 rpm (like mine) and worst before it reached operating temperature (like mine) Funny thing is, his engine doesn’t have balance shafts and was not rebuilt. So, I’m still lost. All I’m really sure of is that the car was much smoother before the pistons were replaced.

The vibration seems to be twice as fast as the rpm. Take a look:

I’ve heard that incorrect reassembly of the balance shafts is a common mistake. The engine mounts will be more firm when the car is started in the winter, and vibrations are usually worse. Maybe you have a resonating vibration that actually gets better when the mounts are cold?

1 Like