Two problems. Are they related?

**jman44** · 07-16-2013

So i have a 99 grand prix gtp coupe. Black, sharp car, i love everything about it but more and more problems keep popping up! So i Drive my car to winchestor to get some food and as the guy infront of me orders the whole menu i get it sit behind him and wait. So as i am sitting there i hear this sound coming out the rear of my car. It sounds like air. (like if you put a open end on a compresser hose and it blows air, it sounds like that with a little less pressure behind it.) What i cant figure out is what is it? The only thing back there is fuel, brake lines, and the fuel pump? Right? If the lines had problems i would fine out fast. Ruled them out i think. Is it the fuel pump?

Next problem is when i am driving the car and get on it(around 4k rpms) the car will start to like studder like the fuel is momenteraly stopping. When i watch the rpm gadge when it happens they jump with the car so its something fuel right? Maybe?

Any help would me much appreciated. I am not a mechanic (no Where close) so these are just my guesses. Thanks for your answers and knowledge!

**99PontiacGTP** · 07-16-2013

Not sure on the sound, could be a loud fuel pump? Mine makes noise when I'm low on fuel. That's more of a buzz as opposed to a air sound.

The sudder sounds like a transmission slipping. If you lose fuel the rpms would drop not jump. If the transmission was slipping it would shudder and the rpms would jump as the engine starts to free rev.

**Scottydoggs** · 07-16-2013

did the air sound stop? or continue the whole trip? did it sound like it was coming form the rear wheel well area?

only thing i can think of is a line to the canister from the gas tank popped off, or cracked. when its hot the gas fumes expand and cause some pressure in the tank, if it blew a line. this air sound would run out of air soon after id think, then set a code for the evap system sooner or later.

**jman44** · 07-16-2013

does it mean the fuel pump is bout to go out? and the rpm's go down then jump back up

**jman44** · 07-16-2013

the sound has been doing it for a while i will look under it tomorrow, i am looking ontop of the tank correct?

**jman44** · 07-16-2013

yes it is coming from rear wheel well area

**SlowNA06** · 07-16-2013

How many miles are on the car?

Originally Posted by jman44

i hear this sound coming out the rear of my car. It sounds like air.

Checked your tire pressure? Perhaps the spare is leaking?

Originally Posted by jman44

when i am driving the car and get on it(around 4k rpms) the car will start to like studder like the fuel is momenteraly stopping. When i watch the rpm gadge when it happens they jump with the car

Hit up an autoparts store and they can check for error codes for free.

If no codes are present, I'd bet on air, then spark before considering fuel.

Air:
Check for vacuum leaks. The #1 cause of your symptoms is that the rubber "T" under the supercharger snout has dry-rotted.
New air intake filter.
Clean mass airflow (MAF) sensor wires with MAF cleaner spray.
Clean throttle body plate front and back with throttle body cleaner, toothbrush, and a rag. Don't spray it down the intake. Block the plate open for like 20 minutes afterwards to let it evaporate out.
Put it back together. The first start might be slightly rough. It's normal.
Go for a test drive.

As far as spark:
The sparkplugs and sparkplug wires are good for 100,000 miles as long as they're stock iridiums. You can pull one of the front plugs to check. If it's not ACDelco Iridium or it's fouled or broken, replace them.

**SlowNA06** · 07-16-2013

Originally Posted by jman44

yes it is coming from rear wheel well area

Driver side or passenger side?

**jman44** · 07-16-2013

150k miles, no tires leaking check them and the spare is good, I changed all plugs and wires 2.5k miles ago, I did get it read any it came back maf sensor could be bad or something todo with maf. i will also check all that tomorrow and hopefully i cant fix this problem

**jman44** · 07-16-2013

Driver side

**jman44** · 07-16-2013

can fix this problem lol

**jman44** · 07-16-2013

And i just put a cai on it.

**Scottydoggs** · 07-16-2013

the canister is in the wheel well, if you pull the plastic liner off you'll see it. if facing the tire, its to the left.

the surging of the engine could be from a vac leak if a line blew off or broke.

the maf code, check the wires to the maf for cracks or missing insulation, bad wires can make the low voltage code pop up.