Engine Loud Humming->oil Pressure Tanked->rpm Tanked

[LoveTheGains]

Hey guys,

It's my first time posting here and hoping to get a little help. I purchased my mustang about 2 weeks ago. It's a VERY cold day and i start my mustang, I then go out to clear snow out of the windshield(took a while). When I come back in my engine starts a VERY loud humming sound, when it stops the oil pressure tanks all the way down and then the rpm's tank all the way down(all on idle). I turn it off then on again and the rpms range between 400-750 sporadically(idle). I turn it back off and check the air filter then turn it on again and just drive off.

I've heard this noise(almost sounds like a cruise ship taking off) before and one time was able to open the hood to try and check where it was coming from. Originally I thought it came from the left side but it seems to be coming from under/around the air filter on the right. Nothing seems to be wrong with the air filter or any blockages.

Two more things to note, the mustang does have a fuel leak I've been meaning to get fixed. Whenever I park my car up hill and the tank is decently full it will leak near the tank. Also I believe the previous owner used 89 octane fuel, I used it for a while but then a friend of mine told me it runs better on regular so I recently switched to that about a week ago. Maybe its in my head but I feel like it has been riding better. How bad is it that i changed up the gas?

I appreciate any help I can get! Thanks a lot!

 

[vertigasen]

First, what year and model is it? 96 GT? 04 Mach 1? That can a huge help since the information here is a bit......vague.

Hey guys,

It's my first time posting here and hoping to get a little help. I purchased my mustang about 2 weeks ago. It's a VERY cold day and i start my mustang, I then go out to clear snow out of the windshield(took a while). When I come back in my engine starts a VERY loud humming sound, when it stops the oil pressure tanks all the way down and then the rpm's tank all the way down(all on idle). I turn it off then on again and the rpms range between 400-750 sporadically(idle). I turn it back off and check the air filter then turn it on again and just drive off.

What do you mean? When it stops the oil pressure tanks all the way down...... When WHAT stops. The loud humming sound? The engine? You also say the RPMs tank, so I am guessing it is just the sound that stops, and the RPMs drop. If you press the gas to get the RPMs back up, does the humming start again? You say the RPMs range between 400 and 750......that is normal range, but is it pulsing? Dropping to 400, then shooting back up to 750? The oil pressure, do you have an oil pressure gauge or just the dash gauge? If your car is a 97 or later, the dash oil pressure gauge is just an ON/OFF switch. If your pressure is above 6psi, then it shows good oil pressure. If that gauge is dropping to 0, that means you have less than 6psi of oil pressure and that could explain some of the hum right there! More info is needed!

I've heard this noise(almost sounds like a cruise ship taking off) before and one time was able to open the hood to try and check where it was coming from. Originally I thought it came from the left side but it seems to be coming from under/around the air filter on the right. Nothing seems to be wrong with the air filter or any blockages.

Two more things to note, the mustang does have a fuel leak I've been meaning to get fixed. Whenever I park my car up hill and the tank is decently full it will leak near the tank. Also I believe the previous owner used 89 octane fuel, I used it for a while but then a friend of mine told me it runs better on regular so I recently switched to that about a week ago. Maybe its in my head but I feel like it has been riding better. How bad is it that i changed up the gas?

I appreciate any help I can get! Thanks a lot!

The fuel leak is probably the Fuel Tank Filler Grommet. It is the rubber seal holding the filler neck in the tank. Its an easy fix, but you have to drop the tank. Also, be careful removing the filler neck. There is a plastic piece on the end that holds the anti-siphon spring. It can easily be broken if you just try to yank the thing out. Take your time, use some lube, and pull it out straight. I broke my first one because I was in a hurry! As for the gas, a stock GT does not require special gas. 87, 89 octane is fine. If it is tuned for a higher rated octane, then that is what you need to follow. DOHC (Cobra and Mach 1) engines REQUIRE premium gas.

Here is something I saved a long time ago....

Only use Premium if you have;
1. advanced timing
2. increased compression ratio (the general cut off from regular to premium is around 9.8-10:1 depending on the car and driving conditions)
3. forced induction of any sort ie nitrous, SC, Turbo

I'm going to add a fourth option here though.
4. If you feel your car pinging or knocking, try bumping up to 91 octane, if it goes away then you DO in fact NEED to use premium gas. (Pinging will sound like marbles in a can when you try to accelerate).

J