98 V70 non turbo - engine drones when accelerating

[98v70dad]

My car has 130K miles and it makes an odd noise when accelerating. The noise is subtle (not too loud) and some of my non-mechanically inclined friends can't even hear it. It seems that the noise is coming from the engine bay but its hard to say. The other thing I've noticed is that I get a vibration that matches the sound that I can feel through the accelerator pedal.

I really have no idea what this is or if its something to be too concerned about. I've done the PCV rebuild and I've replaced the front lower engine mount and the upper torque mount. My gas mileage is in the 20-25 mpg range on the highway but the car has zero pep. There is a hill I have to climb from a stop at a stop light and the car just limps up the hill. Once its moving the car is OK but from a dead stop on a hill it just barely goes. The reason I mention this is I'm wondering what in the fuel injection delivery system might cause that very subtle drone and vibration? The car could probably use a new fuel filter. The fuel pump is the original and as far as I know the fuel injectors are also original and have had no maintenance. I last changed the fuel filter about 3 years ago but that corresponds to only about 20,000 miles. Plugs, wires, rotor are all OEM and replaced about 2 years ago, but I did the plugs etc and then the PCV system afterwards only recently

Any other thoughts or ideas? Any input would be appreciated. I'm not convinced it has anything to do with the fuel system...maybe I have a fouled plug or plugs...don't know where to start.

[jblackburn]

Like a whining type droning noise or more or a low-pitched somethings-rattling-against-something noise?

Fuel filter would not be a bad preventative maintenance thing to do anyway. Worth having a look at the plugs just for curiosity's sake - they can tell you a lot about how the engine is running (rich, fouled, lean, etc), but it doesn't sound like it is misfiring.

Highway gas mileage and power both being low - I'm curious - if you get under the car and try to shake the catalyst, does it make any sound?

[abscate]

Poor power is rarely fuel delivery. It feels like " it isn't getting gas" but that's a useless diagnostic.

Compression check..rule out engine damage
Spark plug evaluation
When was the coil last replaced?

Then move to fuel.

Fuel filters last 100k on these cars

[98v70dad]

Like a whining type droning noise or more or a low-pitched somethings-rattling-against-something noise?

Fuel filter would not be a bad preventative maintenance thing to do anyway. Worth having a look at the plugs just for curiosity's sake - they can tell you a lot about how the engine is running (rich, fouled, lean, etc), but it doesn't sound like it is misfiring.

Highway gas mileage and power both being low - I'm curious - if you get under the car and try to shake the catalyst, does it make any sound?

It will be a few weekends before I can do that. I've wondered about the exhaust system too. I've been planning on getting under there and looking for cracks. The droning is a bit like the sound I got from a cracked exhaust I had in a high mileage camry. Its definitely not a rubbing sound or metal on metal vibration. I'll check the cat while I'm under there looking at the exhaust. I did a seafoam treatment about 8 months ago (sipping through a tube attached to the intake vacuum tree) and a good bit of white smoke came out of the exhaust manifold area. I thought this was odd at the time but several people told me the same thing happened to them. Now I'm thinking maybe I actually do have a crack in the exhaust.

[98v70dad]

Poor power is rarely fuel delivery. It feels like " it isn't getting gas" but that's a useless diagnostic.

Compression check..rule out engine damage
Spark plug evaluation
When was the coil last replaced?

Then move to fuel.

Fuel filters last 100k on these cars

I've been wanting to do a compression check but I dont have the tool and I've been putting it off since I also dont have loads of free time. I agree that the fuel filter should be fine. The coil has never been replaced as far as I know. The car was 10 years old when I bought it. I was intially more concerned about the droning sound than low power. They could be related or not....

[jblackburn]

I did a seafoam treatment about 8 months ago (sipping through a tube attached to the intake vacuum tree) and a good bit of white smoke came out of the exhaust manifold area. I thought this was odd at the time but several people told me the same thing happened to them. Now I'm thinking maybe I actually do have a crack in the exhaust.

My (T5) did that too.

The flex pipe is a common leak, as are the clamps at the cat converter.

[kahl]

On every one of our V70s have had a crack that appeared after the cat. In addition one had a leaking exhaust manifold gasket on one cylinder. I used a piece of tissue on a stick to find the manifold leak.

[98v70dad]

On every one of our V70s have had a crack that appeared after the cat. In addition one had a leaking exhaust manifold gasket on one cylinder. I used a piece of tissue on a stick to find the manifold leak.

The seafoam smoke actually looked like it was leaking from around the exhaust manifold gasket but it was a little hard to tell for sure. I didn't get the giant cloud of white smoke that goes on for a long time. There as a big puff from the engine area and by the time I got over by the aft side of the engine bay to look at it it was over.

How did you fix the gasket leak. Obvious answer would be to replace the gasket, but is ther something simple that works ... like tightening the bolts?

[kahl]

I am not aware of any compound that can be applied to a leaking manifold gasket. In one of my posts I showed a picture of the eroded gasket. For me it was an eight hour job. If you remove the heat shield on the back of the motor and move around a tissue on a stick you can see if your manifold is leaking. A lighted mirror helps you see all around the five exhaust gaskets and the turbocharger coupling.

[mika]

no one mentioned this: are you driving in (n)ormal mode? switch that to sport! Makes a big difference once ECU learns your non granny driving style. I used to only drive on normal, and then made the switch to sport and never looked back