Need help. Car can't go over 30mph without feeling like its gonna die..

[D Unit]

Car is a 2004 4.8is. Maintenance history is here...
https://docs.google.com/spreadsheets...gid=1979265047

While driving today, my car all of a sudden started stuttering, hesitating, won't go over 30 mph without feeling like the idle is going to die. I basically had to limp it 4 miles home around 20 mph. Once I go passed 25 - 30 mph, the car starts stuttering hard and feels like it's not getting any gas or spark...not really sure.

It kind of reminded me when I had misfire on my e36, so when I got home I changed out my spark plugs to the OE NGKs. Problem was still there. I though I read it might be the torque converter, but when I drive the car using "steptronic?" and shift gears manually, it still has the exact same symptoms.

I tried using INPA to get the error, but this was the best I could do. Does this mean anything?

[puddinboo]

could be your maf sensor. just a guess though.

[ants_oz]

When was the last time your fuel filter was replaced?

Did you fill the tank with fuel recently? Was it from a place you usually fill at? Is there the potential that the fuel was contaminated or dirty?

My bet would be fuel-related.

At a guess, you can accelerate gently and not experience a problem until the vehicle starts to load up, but if you accelerate hard off the line, it will exhibit the symptoms.

[D Unit]

Originally Posted by ants_oz

When was the last time your fuel filter was replaced?

Did you fill the tank with fuel recently? Was it from a place you usually fill at? Is there the potential that the fuel was contaminated or dirty?

My bet would be fuel-related.

At a guess, you can accelerate gently and not experience a problem until the vehicle starts to load up, but if you accelerate hard off the line, it will exhibit the symptoms.

Funny thing is my wife "did" just refuel with a full tank. She told me she was 99% sure she put 91, but after pressing her, she said she's not sure anymore. But your description is right on the money... I can slowly accelerate and get up to 50mph, but then it starts to bog down. If I floor it from a stand still, it will bog down. If I floor it from 20mph, it will bog down. But if I slowly accelerate, I can get up to 50mph.

There's a gas station near me that sells race gas. I'm still at 3/4 of a tank, but do you think it will help if I topped it off with 100 octane (or whatever the highest they have over there)?

[ants_oz]

IMO, the wrong octane (too low) will not result in the symptoms you described - it will simply result in a lack of outright performance. The vehicle should still run quite well.

My money is firmly on dirty fuel which has clogged the filter. If it were smoking like a biatch I would say she's filled it with diesel.

[D Unit]

Well, I just put in 10 gallons of 100 octane fuel at about $9 per gallon.... $90 later, still the same thing so I guess I can rule out the gas.

I'm going to drive this car to the shop and have them change out my fuel filter first before they trouble shoot. I'll keep you guys posted if that works.

[ajstefanacci]

Originally Posted by ants_oz

IMO, the wrong octane (too low) will not result in the symptoms you described - it will simply result in a lack of outright performance. The vehicle should still run quite well.

My money is firmly on dirty fuel which has clogged the filter. If it were smoking like a biatch I would say she's filled it with diesel.

Diesel nozzles are lager and don't fit in gas cars. gas nozzles do fit in diesels though. it would work but she would have had to hold it in position and possibly be sprayed with it since it won't slide down the hole.

[upallnight]

Sounds more like a fuel pump going BAD. Could be that the pump is not spinning fast enough to create the pressure necessary for the engine to run right. Connect a pressure gauge to the fuel rail and see what type of pressure you have.

[04e53x5]

I had the exact problem it ended up being a clogged fuel filter and a bad fuel pump.

[D Unit]

Originally Posted by 04e53x5

I had the exact problem it ended up being a clogged fuel filter and a bad fuel pump.

Car does have 142K and and I am not sure if either has been replaced looking at the PO maintenance history. May I ask when did your go bad and how much it cost to repair?