Car sounds like it's idling rough, but rpm rock solid at 700 +-15.

Replaced engine mounts, trans mount, MAP sensor, Pcv valve, plugs, coils, air filter, fluids, rotors, calipers, brake hoses, control arms, struts, stabilizer links, sway bar bushings, outer tie rods, inner tie rods, intermediate shaft bearing, timing belt kit, ac system, rear main seal, have cleaned throttle body.

I've probably done more but forgotten as I've been chasing this problem for 20k miles. Car has 170k on it.

Problem is less severe in neutral and park, worse in drive while stopped with foot on brake. The car itself is not vibrating but you can 'feel it rumbling'.

I'm at a loss, torque converter? Valve adjustment?

 

The car is not vibrating but you can hear it rumbling......

??

Did do you really think changing the brake hoses would help while the vehicle sits in park?

Cracked exhaust manifold?
Hole in downpipe/flex pipe/muffler?

Your choice of essentially random parts to replace is quite thorough. I could justify the mounts if you said the car was vibrating, but you specifically state the car is not a vibrating.

However, you have not told us where the sound is coming from, whether it happens when the car is actually moving, nor when it is the loudest.

 

Hi Derf,

Thanks for prompt reply.

The parts replaced are various parts that have been replaced over the past 3 years. Of those the mounts, MAP, PCV, fluids were all done chasing this problem. Rest are just various things that had to be done or I wanted to do.

Prior to the mounts being done, the cab would shake enough that if you had a cup of water in the console it would shake the water in the cup. Since the mounts that's greatly diminished. It's pretty smooth in the cab, maybe some slight vibration in the steering wheel, but not catastrophic.

What it seems like is the engine or drive train is vibrating more than it should, but the mounts are doing their job and dampening it. When we got the car at 100k it didn't do this.

The vibration does not happen when you let off brake and press accelerator. It actually feels like it smooths out. We do get vibration at 80+mph on freeway.

Appreciate working with you on this thank you so much!

 

I believe you said that the idle was rock steady.
Are you measuring that by looking at the gauge or via a scan tool?.

Things wear and change with time. The crankshaft harmonic balancer is probably not dampening 100% of the vibrations it used to if for no other reason then the crankshaft is not weighted exactly the same anymore. And neither is the balancer. I wouldn't expect any vehicle to run A1 Plus super smooth forever. I'd rather have it jiggling water in a cup then spraying it out through the reservoir cap. It will never be as perfect as it was without a whole lot of money, a whole lot of time, and a whole lot of no real point in doing so.

My advice is to enjoy what you have.
That and to measured the idle speed with a scan tool.
I think you can do idle relearns for the throttle bodies on these vehicles. But first check to see if it's within spec.

​​​​​​Vibe at 80 plus is something else entirely.

 

Hi Derf,

Sage advice! I have used an OBD2 scanner with live data and the rpm at idle fluctuates 650-715. The gauge stays very steady too. I did look at manual and it said 700 +-15, so within spec.

Interesting you said harmonic balancer, that was something I thought as well. I was going to replace the serp belt, pulleys, and tensioner and thought maybe I should do the harmonic balancer while there. Any reason you wouldn't suggest doing so?

I work on a PC all day so working on the car is sort of a fun side hobby where I don't need to deal with people or programming lol.

 

Derf, would the vibe at 80 plus be one of these?

Wheel balance
Wheels out of round
Wheel hub/bearing
CV axles?

 

Wheel bearings tend to sound like a jet airplane at much much lower speeds.
Most wheel balancing issues are 55 to 65 miles per hour

I'll take slight out of round wheel for 600, Alex.
Or some other not obvious resonance you will never find.

You seem to be the perfectionist programmer type. I'm well acquainted with that affliction though not a programmer. Something's going to vibrate at 80 plus miles per hour. Everything is imperfect. It's just a question of how imperfect. You are probably replacing half of the **** with **** that is more imperfect than what you already have.

Bad bearings on pulleys usually screech.

Please stop replacing stuff of unknown condition with other stuff of unknown quality nor condition. These are parts that other people badly need.

I know you have the self-control.
But you have to want it.
That much of a dance in the idle doesn't seem quite right.
I have plus or minus 10 on a four-cylinder made 15 years earlier with dumber control logic and a rougher engine.

Have you cleaned the IAC and throttle body? No don't replace them, clean them. I am not sure but cleaning the throttle body might require an idle relearn procedure or a throttle position relearn.

Could be a tiny tiny tiny tiny tiny tiny tiny vacuum leak somewhere. No, do not replace each and every vacuum line nor the entire engine nor the intake manifold gasket.

There will be an answer.
Let it be.