Long story: water got in the fuel tank because I told my nephew to put the leftover mower gas into the car. He thought I meant the blue jug, which was water. About 2 gallons. OK, I'm in trouble.

I pulled the fuel filter, jumped the fuel pump relay and pumped out milky gas water mix until I got to clear gas, then I pumped out another gallon of gas. I added two bottles of HEET water eliminator and put 5 gallons on fresh premium in the car. I purged the fuel injector rail, then installed a new fuel filter. the car cranked almost immediately and idled fine and revved fine in PARK. Then I drove it and it ran fine until I hit a mild grade. Sputter , sputter sputter .. CHECK ENGINE. I got it back home, shut it down, checked everything. P0300 code random misfires, no other codes. Restart, idles fine, revs fine, sputters and dies under load..

My sisters neighbor who is a Euro car mechanic said that he thought I killed the fuel pump or at least the filter block that goes on the end of the fuel pump inside the plastic cup of the pump assembly the actual fuel pump lives in. Before doing that I replaced the fuel pump relay, but it made no difference.

I ordered a new Bosch fuel pump from Rock Auto and 2 new O-rings and install the new pump. It runs a little better, but not perfect. I find a vacuum leak and fix it and the rubber pipe from the air cleaner box which had a loose clamp loose at the throttle body end. It runs better, but not perfect. I still get sputter s and P0300 codes.

Here's my thinking: get rid of all the old gas and replace the spark plugs and see. Any suggestions?

 

Wow. Nobody has had anything to add to this in a month. That obscure, huh?

In case anyone would like to know, the water in the gas turned out to be a minor issue. The fuel pump may not have even been bad. The relay I swapped in was marginal and it was dropping the voltage, thus the fuel pressure, when under acceleration. Then I had a least three bad coil packs all at once, so it got a new set of five. The MAF sensor got cleaned, and the fuel injectors got cleaned, and it still wouldn't run without balking or stalling at more than idle. Then came a rebuilt throttle body. After the rebuilder sent a second one because the first was either misprogrammed, wrong part or got through QC when it shouldn't have, the car ran. Problem solved, and it only took a month (#sarcasm). Now on to the ball joints.

 

Wow - sorry you had a tough month. It reads as many confounding and confusing issues. On the water /fuel issue, I wonder if there is a drain plug at all on the lowest point of the fuel tank? Either way, after pumping all you could out, I might have left the car with the tank open to the air at the filler and found a way to warm the tank to accelerate evaporation of all fuel and water residue. Heating the bottom of the tank through the warmth of a 60W light bulb or something beside the tank.

Was the relay to the fuel pump the real point of issue? Maybe you suffered under acceleration with that - but wonder if it delivered enough fuel at idle to not explain the rough idle. Maybe the root cause was the throttle body?

Anyway - you must have kicked a black cat or something to have all this happen at once. Hopefully you have earned a few years of hassle free motoring with the car.