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2008 Ford Edge 3.5L - engine vibrations through RPM range


msa04

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Hello All,

 

I have a 2008 Ford Edge 2WD that I have owned since new in late 2007. Current mileage is 145,000.

 

A recent behavior has surfaced with the vehicle - when the vehicle is stopped and in Park or Neutral, a vibration can be felt as you work the engine through its RPM range. The vibration is not noticeable at idle, but it starts at around 900-1000rpm and progressively gets worse as the RPM rises (I tested up to 4000rpm). It's a slight vibration that can be felt through the steering wheel, but it is not vibrating the entire car.

 

Engine has great power and the transmission appears to be fine. Vibration is also present when the vehicle is moving, but is harder to notice since the the vehicle is moving. This vehicle has been maintained very well, so I'm reaching out to you all to help me get to the bottom of it.

 

This appears to be strictly engine rotating assembly or accessory related. Are there any known issues with the 3.5L engine that has these early symptoms? Prior experience with other vehicles make me think it's quite possibly a harmonic balancer issue, but the balancer isn't showing symptoms of separation or run-out.

 

I was reading about the internal water pump issues of the 3.5L on this forum - is this possibly an early sign of water pump failure? I'm planning on checking oil and coolant when I get home to see if there are signs of mixture happening.

 

Thanks in advance for any help.

 

Mark

Edited by msa04
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Next up would be the accessory belts and tensioner, especially if original to the car. The oldtime test would be to take a belt off and see if the vibration goes away. Problem is one of belts (power steering I believe) is a stretchy belt. You should be prepared to replace these belts (and probably the tensioner).

 

What is the recent service history on this Edge, particularly predating this vibration issue?

 

If the engine is running fine, it probably won't be spark plugs/PCV/coils.

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Most recent service other than oil changes is plugs at 120k and transmission turbine speed sensor at 105k.

 

The vibration just recently started, I'd say the last 500 miles. At first I assumed tires out of balance, but then I noticed it was vibrating when stopped.

 

I will do as you mentioned and remove the accessory belt and run the engine and see if vibration remains. I'll go ahead and purchase the belts tomorrow...they could probably use replacing anyway. I didn't get a chance to pull the belt off good afternoon.

 

Thanks for your help.

Edited by msa04
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My 08 Limited had a buzzy vibration that was hard to nail down. I felt it through the throttle but since its an electronic drive by wire, there is no direct link from the throttle to the engine. I presume I felt it because it was the closest to the engine. It turns out that the air intake boot from the air filter box where it connected to the throttlebody was loose.

 

If the vibration is more severe, sort of rhythmic instead of buzzy, it may well be a plug or coil failure. My older F-150 had that issue a couple of times.

 

The vibration frequency and intensity can all direct you to the possible cause.

  • If it feels like someone is bouncing a leg (like someone behind you at a movie theater), I would lean to a tire or wheel defect, especially if it is more noticeable from 40 to 70 mpg. Since you say you feel it while stopped, look elsewhere.
  • If it is more frequent or higher in pitch, remember the engine turns about 3 times the speed of the tires.
  • The water pump cannot cause this problem, nor can the air conditioning compressor, they are too small rotating mass and will not change dynamic balance. If it is the compressor, or even close to it, the AC will not be working.
  • If it is any of the drive belts vibrating, as said above, one of them is a stretchy belt and gets tighter as it heats up. I have seen tensioners go bad but usually I notice slippage instead of vibration.
  • Any driveline mount failure will transmit the vibration to the chassis, and not in itself create a vibration.

Is a Service Engine light on? I am leaning towards a plug or coil.

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Thanks for the input. I'm doubting it's an ignition problem because the engine is not experiencing loss of power. CEL is not on. It truly feels like something is out of balance in the rotating assembly. Vibration can be felt on the steering wheel as you move through the rpms all the way up to 4000 in park. It's a constant frequency at a single instance and increases in frequency and intensity as rpms increase. Exhaust note is normal without hiccups as well.

 

Replaced the belts today and I ran the engine without belts - vibration is still there. The harmonic balancer is not showing signs of separation so I'm assuming it is ok - not completely ruling it out yet.

 

The top engine mount isn't separated (I took it out). I'll check the other mount this weekend.

 

I'm at a loss at this point. I might actually take it to the dealer if I can't isolate it this weekend.

Edited by msa04
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Just kidding....

 

They've been great so far. Cost is the same as stock. Build is the same too.

 

Old COPs had 175,000 miles on them. Old plugs had 75,000 miles. While I was there I changed both. I think I'll go to 50k on my next set of plugs.

 

What I began to notice was stuttering or missing under load. With the new plugs that has vanished.

Edited by autom8r
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