Engine vibration on 95 q45?

[stickw12]

I have recently purchased a 95 Q. The car only has 60k miles. The car starts and idles fine, overall the car runs good, however there is a minor vibration at certain rpm levels, the biggest around 2400 even if i rev in park. I have tried to do a lot of self investigating and have found that the crank pulley moves/vibrates a little bit. I had this replaced by the infiniti dealer thinking the old pulley was going bad. The new pulley still vibrates, just not as much. I was wondering if this is common on this year Q?

I have all of the maintanence records and the plugs have never been changed. I wondered if possible this might be a cause for a minor miss at certain rpms to cause the engine to run a little rough. I have had experience with a 93q a while back, and that car screamed through the gears, this car does not seem to have the same umph! I understand it is 9 years old. Previously it was owned by an old couple and maintained very well, probably never reved higher than 4000 rpms. I have read all the threads possible about carbon buildup and for the specific rpm problem and am not sure it is this.

Any kind of feedback would be great, and if you have more questions I will answer as soon as i can.Thanks

[rsiwicki]

the 90-93 Q's were much faster than the 94-96 Q's. The gearing in the trans is different in the 90-93 for better acceleration (7% faster first gear) and there were two HP peaks for the 90-93 versus just one for the 94-96 Q's and the 94-96 are heavier. I have never driven a 90-93 Q but many have said how much faster they are compared to the 94-96 Q's. Just keep in mind that if you transmission ever goes in your 94 that you can install a 90-93 transmission instead of a 94-96 to regain some of the acceleration performance without any issues. I did this on my 95 Q45t and about 3 others have done the same without any issues.

At 60K you are definitely due for the major 60K service which includes plugs.

[stickw12]

Does your crankshaft pulley vibrate at all? Any ideas on that issue, or change the plugs and go from there.

[rsiwicki]

no idea about the crankshaft pulley thingy.....I am sure others much more knowledgeable than me will chime in sooner or later. good rule of thumb is to always start with the basics making sure all regular maintenance is on schedule and completed and then go from there.

[DAEDALUS]

Are you certain it's the pulley and not the entire engine? Pulley should be pretty much dead-nuts centered; any eccentricity probably shouldn't be visually apparent. I suppose you could turn the crank by hand and check the profile with a dial indicator affixed to the block.

[areznik]

I noticed such minor vibration between 1500 - 2500 rpms on my Q ('94 117K) and as long as I have it the vibration is very minor but its there. I have new NGK plugs so I would not attribute plugs to this problem. I would be more inclined towards motor mounts or maybe even MAF that misreads air flow in this range. Also, if I recall correctly, after a can of BG44K the vibration is barely noticable. Try it and see - never hurts.

Andre.

[maxnix]

How are the motor mounts? How much movement of the engine when you rev it in neutral?

[elwesso]

Is it a very "booming" noise...

I had the same thing on my 94.5 Q45 (basically a 95) and the problem is in the exhaust, there is a TSB on this, for 94 cali model Q or 95-96 Q... Theres another baffle thing you have to install... I lived with it..

It would do it in park, or 50mph in 3rd gear or like 80 in OD...

MY crank pulley moves around a little bit.. Its meant to be that way (i think) to counteract the engine..

[stickw12]

When I rev it the engine seems to rotate very normal compared with any other vehicle I have ever owned. If the mounts were bad would it be very stiff and have little movement or would it be sloppy?

[stickw12]

I am not sure what you mean by booming noise. I also don't understand the acronym TSB (sorry). But I will say out of all the post you sound like you had the most similar problem. the rpm where it is the worst is right around 2400, which is around 70ish miles an hour in drive. But you can still feel it in other rpm ranges. I am not sure how the exhaust would effect this but if you could explain further I would greatly appreciate it. Another symptom is when the engine is under a pretty heavy load (high rpms in 3rd gear, yes, way over the speed limit) there is a heavy semi slow wave of vibrations and the car can't hardly make it to fourth gear. please let me know what you think. Also, what was your solution for your problem?

[texasoil]

Carefully inspect the rear engine (transmission) mount. These will sag and just touch the crossmember,setting up a resonate vibration. Very hard to 'see' the sag--but you must be able to slip at least 1/4" thick stich betweem mount and crossmember. Also check exhaust hangers for hardening, especially the ones by the transmission rear. The body has a natural frequency that +/- 2400 RPM's excites. Soft exhaust hangers and good transmission mount are key.

[maxnix]

It would be sloppy. I think a movement of 2" was cited once long ago.

TSB are Technical Service Bulletins, essentially supplements and corrections to the FSM (Factory Service Manual).

By "...the car can't hardly make it to fourth gear" do you mean it has trouble shifting into fourth at high speed and load? This sounds unrelated to any engine condition, but rather a transmission problem. Then again, the wave of booming low frequency vibrations makes me suspect the exhaust hangers.

Ever replaced the rear engine (transmission) mount and the associated exhaust hangers? How does the ATF look?
Modified by maxnix at 4:21 PM 4/9/2005

[stickw12]

Great input, and thanks. I would say the engine mounts seem fine, they are not sloppy, if I were leaning either way it would have been stiff. 2 inches sounds right. I also did some more research about the TSB, by the way, when I hit the post button a light went off in my head on what it meant. After hearing what you guys have said and about the harmonics of vibration from the car this very well may be the cause, are these mounts easily replacable? Also, do you know what the fix is for the TSB? I am going to go look at the car right know and try to look at the transmission and crossmember. however the ATF looks very clean. any more imput would be great and if you have any way of testing the exhaust hangers let me know. Thanks

[stickw12]

Oh, sorry, the shift to fourth would not be the transmission, I just felt it was not good to keep pushing it any harder at the 6000 range, it was not getting to 7000 real soon and had pretty noticable vibes. The transmission shifts pretty strong.

[stickw12]

Ok, I have no clue what to look at as far as transmission hanger and transmission sag, I will have to have a friend who is a mechanic look. however placing my hand on either one of the exhaust pipes all the way back feel extremely stiff. I cannot get them to move hardly at all with a decent amount of force. I would imagine the hangers have just hardened(if they aren't supposed to be that stiff, you tell me).

[maxnix]

I would imagine the hangers have just hardened(if they aren't supposed to be that stiff, you tell me).

Well, that's what happens when they age. They lose their elasticity and don't suspend anymore.

The transmission (center rear engine) mount needs only to have settled to a 1" or even less deflection to require replacement. Best seen on a lift.
Modified by maxnix at 1:21 PM 4/7/2005

[DAEDALUS]

May not be readily apparent visually until you actually replace it. Just before you replace it the transmission is resting on a stand. As you torque up the mounting bolts on the new mount, they will lift the transmission off the stand. The gap between the transmission and the stand is the sag, plus some distance that was actually supported.

[96Qowner]

When texasoil mentioned the transmission mount it reminded me my former vibration. I searched the archives for every thread on the subject and decided to try replacing the transmission mount - that fixed it, and others have also said it fixed theirs too.

My vibration was centered a bit higher than yours, but otherwise very similar. Mine was worst at 2250 rpm in all gears and it diminished as the rpms went both higher and lower. I had also decided to try the exhaust hangers if the transmission mount didn't work.

Here's a thread from wes on the subject:

BTW, my transmission mount was a fuggin mess - REALLY bad.

zerothread?id=92683

His wasn't the transmission mount, but there's good info from everyone in the thread.

[wlong]

I had a similar vibration in Park at 2250 rpm and at the same RPM in each gear (~70mph in OD). I looked at the TSB that Wes mentioned and other posts and decided to replace the rear transmission mount since it looks like it goes out every 80-100k. Once I removed the mount, it was obvious that it was broken (rubber broken in one spot). This basically fixed the problem although I still have a very slight vibration that I am living with at this speed that I attribute to the exhaust issue discussed in the TSB. If I did not have the mount problem, I more than likeky would not have noticed this vibration.

Changing the rear mount is easy. Maybe an hour. It cost around $75 from Scottsdale.

[Q45tech]

Same situation with front engine mounts they are all shot by 100k just that they are rarely changed due to labor cost.

Need all 3 mounts [plus exhaust hangers and diff bushings,,,etc] new to fully derive benefits..........why a $50,000 car is worth only $10,000 with 100k [7 years] on it..........all the rubber isolated parts need replacing.

[stickw12]

I actually had the car looked at by a professional mechanic and haven't noticed your posts for a day or two. The engine mounts and transmission mount are all being replaced wednesday. They said I had a bad driver side engine mount, and reccomended replacing all three due to stress from one bad mount. I appreciate your imput and will let you know when done how much better the vibes are.

Thanks,

[maxnix]

Good news! Keep us updated, please.

[stickw12]

Got the car back after replacing both motor mounts and transmission mount. The car is vibration free and drives like a q should. When I went to pick up the car I asked to see the old mounts. The driver side mount was in 2 pieces. The inner core completely seperated from the outer. The passenger side was real close to being the same but still attatched in one piece. The transmission mount was also completely toast. Almost two pieces. If you remember this is a 95 with only 60k, my suggestion to anyone with vibration issues is to not only look at the transmission mount, but all three. I guess the one bad thing about buying a car that sat so much is the rubber dry rotted faster than normal, but now the car drives great.

thanks, and let me know if you have any questions.