I have looked all over for an answer to this one, and since this is happening when I rev the engine when standing still, it is not the typical line up of possibilities.

Ok, I had noticed my car ran rough at certain points of acceleration. I thought it was tire balance, the bearings, axle and so on...

Well, I then tried revving the motor in Park. I see that it is when I hit 3000 rpms. Then when on the road, the roughness/ vibration is not so much what gear I am in, it is the MAGIC 3000 RPM mark that makes the condition come to life.

My attempts to fix it:

I tried new spark plugs, gapped to 43 like the shop told me.

I cleaned the TB out with carb spray.

I cleaned the MAF three times now with that special MAF spray.

The ride quality was better, but the problem was still there.....

Not fixed.

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So, I take it to the mechanic, and they say they noted that the fuel pressure drops when the rpms go up.

Their fix is, a new fuel pump.

I notice, after blowing $600, it runs better, but it still vibrates at 3000 rpm on the road and when revving to 3000 in park!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Not fixed.

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My car is an automatic LS 2.2 with the only modification is a 2.25 inch catback exhaust.

I had my tires replaced around November.
They balanced the wheels and had to rebalance them because I had vibration at 70mph.
They acknowledged the wheels were not correctly balanced and rebalanced them.

The reason the tires were replaced:

One of the wheels had a slipped tread/ DEFECT.
The tire created a pull to the left.
They put the defective tire when first put on onto the rear, and never noticed a problem until it was rotation time.
When I realized it pulled left, I just had the alignment checked and they said it was ok.
Then the mechanic said, well, you bought crap tires, it happens.
Not until a few years on these did I get told it was a slipped tread.
So I bailed out of these crap tires and got new ones.

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The only reason I mentioned the tires, was to give the history on this.
Maybe the shaky pull to the left tire wore something out due to vibrations that I did not notice?
The tire only vibrated a few years later, and the only thing I noticed was the pull to the left.

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I am a little upset as I just spent a lot of money on a fuel pump and feel the fuel pressure dropped for another reason other than the pump. I wonder if it is the injectors, or the fuel pressure regulator or????

Does anyone know what caused the engine to project vibration through the wheel and footboard when in nuetral at 3000 rpms?

When I hit 70 quickly and then accelerate gradually after, and the rpms hit 3000+, it then feels really ROUGH, and it sometimes feels like the wheels shake. Even more so when decelerating and is worse when it is cold.

The worse part, is that this condition happens some days and not others.
I tried tonight to see if I could prod it, and the car did not like accelerating to 70 hard onto the freeway.
Then once I leveled out and let a few seconds go by, I accelerated with a gradual pressing onto the pedal and I felt the roughness and the wheels felt like they started to shake. But when I let it go for a bit and tried again, it was not as bad.
It seems random, but I am not a mechanic and really can't picture what is going wrong here.

Please guys, I need help here. I hear so many talk about U joints and motor mounts, but when it happens at idle.... I don't know if it is one problem or a combination of problems.

 

I don't like guessing and i have read all of this, Maybe a video will help... I would like to agree and say injectors or something to due with the fueling, But i am going on what you said and would like someone else's input or a video on this please and thank you.

Also how many km or miles are you at ??
For the fueling system what hasn't been changed ??

 

If I remember right the harmonic rage for the 2.2 is 2950-3080 RPM.

I would check your harmonic balancer on the crankshaft pulley...

just my thought.

oh and to really get, you if you don't check it and it is bad then your going to fry your barrings and toast the block...

then again I could be completely wrong on this. but if it only happens at 3k then....

 

The car is about 82k miles on it.

I was wondering, how does the harmonic balancer go bad?

I will have them check this.

 

personally I have never had one go bad.

I have seen them on other cars but never mine.

Some are made of rubber and the rubber can decay and crap...

It is a long shot but your issue that happens only at 3k sounds about right for that.

 

Have you ever changed your fuel filter?

 

I take back the balancer at this point.... I looked and it is not rubber...

has anyone on here used fuel system/injector cleaner before?

some people swear by it and others say it is a waste.

I have used it before and never noticed and improvement in idle/pick up/MPG so I don't use them.

Just wondering if something nasty got in there and gunked/clogged up a line.

 

Now that some time has gone by, here is some things I noticed:

-When it is colder in the morning or night, the car vibrates in the front end once I hit 70mph and gets worse when I hit 80.... But, driving it around 70-80 for a bit, it then seems to fade away.

-I did some gun it moments and the acceleration problem, that roughness I spoke of around 3000 rpms seems to be less prominent.


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It seems odd how this problem is somewhat predictable and sometimes I try to replicate it and it wont happen at all.... This morning it was hot out, and the car ran like new until I got to work. Then it was a 'hint' of roughness sometimes when accelerating around 3k.

Guess what? When I took it to the mechanic, it would NOT do it at all.

He said, it might be the road and so on. I have driven this car for 7 years and know it very well and the roads I am on. I know that there is something wrong and feel it is a couple problems.

The possible reason for the build up to this problem:

-I took the car recently to get the fuel system service.
-They put stuff in the intake and gas tank to clean it.
-It smelled big time and I worry they revved it too much.
-They did replace the fuel filter at that time.
-It seemed to run fine for a few weeks.


This was the last service I had.

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I noted my lug nuts were not real tight, some requiring a half turn to tighten up!
My front right tire when I turned the lug nuts, it made a pop noise on all 4 when tightened up, when the other 3 did not.

I wonder if:
A) the fuel system cleaning made some of the rubber hosing fray and peel inside which had debris go to my injectors.
B) my front end has a sticky piston on the caliper
C) maybe I have a bushing or connection that is damaged in the front end which when it is hot out, the expansion of the bushing makes for a better ride and when it is cold, it shrinks and I get the opposite.


What bugs me, is I need to have a mechanic drive this IN THE COLD, I am in AZ and it only happens when it wants to which is rarely in the morning, and the mechanic is not going to test this at night as he is going to be home with his family.

What can I do so the mechanic can witness this happen? Cast a spell to make it cold out? LOL!

 

It might be worth it to invest in hpt ( didnt see your year anywhere.. The l61 doesnt support it, but the lap does )
Then you can monitor what exactly the motor is doing. Will forsure help in narrowing down the problem, and make the old girl run a little better too

 

It is an 07 LS model; is the HP Tuners able to work on that year?