Excessive engine noise in cabin/acceleration lag 2001 4.0

[mraurora]

Hi all. My 4.0 has 52k miles on it. I test drove another 01 4 liter to compare and contrast today. It had 100k miles on it and was beat to heck. However, it was tons quieter and so much faster. I bought my car about six months ago and always thought it should be more responsive. I took it to a local shop and asked if they could think of anything that would cause my car to be so much slower than the one on the lot I just drove. He said different cars drive differently and that there was nothing he could do. He did say that there was too much engine noise in the cabin of my car. 


There are no CELs or codes thrown. There is no hesitation on startup or during acceleration. The tach doesn't jump around. I've had all the fluids flushed. Fuel system cleaned, new fuel filter. New engine air filter. Thoughts? I've considered a clogged catalytic converter, a dirty MAF sensor, a clogged EGR valve. But all of those things would come with other symptoms other than laggy acceleration, correct?



As for the engine noise in the cabin, the noise is coming from the driver side cowl area. I always thought it was loud for a 40k car, and apparently I was right as the beater Aurora was quiet as a mouse. Any ideas on that front? I do know my steering shaft was worked on, and the shroud was left off, but I doubt that's where all the noise is entering the cabin? Everything visually under the hood is the same on my car as the one I drove today. All the paddings, moldings, etc. 

[Marc]

I think that some Auroras came from the factory with different tuning. I have also driven 2 2001 4.0s. A demo that I drove back in 2000,and the 2001 that I have now. The demo had no power compared to mine. In fact, my 2001 4.0 runs almost as good as my prior car, a 1972 442 W25 455. A power tuner might help. Google "Oldsmobile Aurora power tuners". And what gas are you using? 93 octane will allow maximum spark advance. As for the engine noise, my guesses are a cracked exhaust manifold, loose exhaust manifold bolts, or a bad exhaust manifold gasket.

[mraurora]

I use 93 octane. Northstar Performance just came out with a PCM tune for the Aurora. I intend on looking into that, but I want to make sure nothing is wrong before I do. My car was built in 2001, so it's a later 2001 model year car. I'll check the exhaust manifold. 

[RCA1186]

Hard to say without hearing it first hand. DOHC shouldn't produce too much noise. The Aurora is usually whisper quiet on the inside as far as engine noise. Some thoughts are,


Do you have the engine cover on still? Do you have the insulation under the hood? Do you have a "cold air (warm air) intake on it? I'd also suggest trying another shop, if there actually is a problem causing engine noise the mechanic should be able to find it.

[paulaurora]

bad front motor mount can make the car not to accelerate well so is not so gr8 front struts. noise most likely some kind of insulation missing or maybe bad hub bearing.

[mraurora]

Aug 12, 2022 13:09:27 GMT -6 RCA1186 said:

Hard to say without hearing it first hand. DOHC shouldn't produce too much noise. The Aurora is usually whisper quiet on the inside as far as engine noise. Some thoughts are,


Do you have the engine cover on still? Do you have the insulation under the hood? Do you have a "cold air (warm air) intake on it? I'd also suggest trying another shop, if there actually is a problem causing engine noise the mechanic should be able to find it.

The engine isn't too loud when you're outside the car. It sounds like a normally operating engine. It's all the noise that enters the cabin from the front driver's side that's the problem. The engine cover is on it. The hood insulation is present. Like I said, all of the visible components under the hood of my car matched that of the test car I drove. So there's nothing visibly different between the two. The intake is stock, I believe. I'll probably have to rip the dash apart to see if the sound deadening materials near the bulkhead (I assume they were manufactured to be there) were removed for some reason. Perhaps the front sunroof drain tubes were leaking and got the padding wet, so the previous owner removed it? Is it possible for the front drain tubes to saturate bulkhead padding?

[mraurora]

Aug 12, 2022 16:30:28 GMT -6 paulaurora said:

bad front motor mount can make the car not to accelerate well so is not so gr8 front struts. noise most likely some kind of insulation missing or maybe bad hub bearing.

Motor mounts and struts are fine, as are the wheel hubs. Actually just replaced one of the wheel hubs. I assume it has to be an insulation problem letting all the engine noise into the cabin. 

[paulaurora]

best maybe put car on the lift and have someone seat inside and accelerate and see if noise present outside. might be drive shaft or axle. I was visiting Florida Tampa if i knew you were in fl we could of had a small meet