tpaulus

I've had two occurrences lately of what I suspect is water in my fuel tank.

The first time was minor, the engine sputtered and misfired repeatedly for up to 10 minutes as I looked it over in the garage. Random misfire codes were registered in the ECU, P0300 etc. I talked to a mechanic who suspected I got some water in my fuel when I refueled earlier that day. It fixed itself and I let it pass.

The second time was worse, the engine would barely run, stall repeatedly and it was persistent. I started it several times over three days with same result. Same ECU codes P0300, etc. Then I added Iso-heet to the tank, let it sit 30 minutes and it started running much better, but not perfect. After 5-10 more minutes and a quick spin through the neighborhood, it was running fine again.

The second time, there was no refueling involved. After the last refuel, I drove it some but then it sat for 14 days in my garage while I was on vacation, with about 1/2 tank of fuel. Then my wife drove it 25 miles round-trip to work. No problems so far. Next day I ran some errands with it, returned home and it sat for several hours. After which, I went to move the car and it wouldn't run properly.

BOTH TIMES though, I went through an automatic car wash immediately before I had the problem. I.E. I ran through the car wash, then returned home...the next time I tried to start the car, the problem was there. That's where I'm suspecting the water came from but not sure why.

Anyone seen anything like this before? Yes, I checked the gas cap and it looks normal to me, other than that I've done nothing.

KyleB

Never on E60, but I remember E36s having a problem with water entering the casing where the engine control unit was housed. We used to get a lot of those, and it seems like all of them were cars that went through automatic car washes. You might want to check your ECU box and make sure it's not getting wet.

EddieboyS

+1. I would suspect moisture getting to engine electronics ahead of water somehow entering the fuel system.

tpaulus

I considered that, but don't think it's the case for 2 reasons.

1. Water in the electronics would have an immediate effect. My problem surfaces after the car sits awhile. If anything, water would have evaporated some during the sit period, not gotten worse.

2. Adding Iso-heet to the fuel tank completely resolved the problem. I concede that could be a coincidence, but I started the engine 3-4 times over several days with same results, including just before adding Iso-heet, it was missing so terrible it would barely run. 40 min after adding iso-heet, the problem was completely gone.

I'm outta town right now but hope to put it in the air over the weekend and take a look. Not sure I know what to look for other than something obvious like a cracked EVAP canister/hose or some anomaly around the fuel tank. If water can get in, I would assume fuel could get out and I'm not having that problem -- no odors in my garage, no change in MPG.

Notheld

Any mods to the car? CAI?

My guess is your using the same gas station to fuel up. If its an old station stay away.

WarpedWheel

Just a thought....
You might keep condensation in the back of you mind. If you are driving around, then go to a car wash, then drive home, you could be getting condensation that could effect electronics. Similar to having a car with a distributor. I could wash the engine in my old Mustang and it would run just fine. It didn't act up until I would run the engine enough to get heat then shut it off. At this point the heat would create condensation from the water that was sitting in the base of the distributor (causing no harm). When I would go to start it again it would run terrible until I dried the condensation out of the distributor cap. Your run time after putting in the Iso-heat could be long enough to finish burning off the last bit of condensation.
Maybe not likely, but it is possible.

tpaulus

I think the clue from the mechanic that it may be water in my fuel was a giant RED HERRING that, when combined with coincidences about the car wash, the iso heet, and my inexperience in dealing with this type of problem, all lead me in the wrong direction. In the end I don't think water was a factor, neither in the fuel nor electronics.

After the iso heet, I ran the tank down to empty, <0.5 gallons of fuel remaining and refueled at another station from my usual (usual is Costco). The engine was running normally, but I noticed a hiccup in RPM each time I started the engine shortly after it was started, then it would even out and run OK.

I took the car to work the next day (35 miles) and then to the airport (another 15 miles), no issues other than the hiccup after engine start. There it sat for 3 days. When I returned from my trip and started the car at the airport, it was missing something awful, barely could drive the car, no power, very rough. Against my better judgment, I drove it up the freeway to the mechanic and left it with him. I wanted him to see it missing for himself, not just hear about it from me -- mission accomplished.

He read 17 codes in all, all cylinders but one reported misses, he also had some lean fuel mixture codes, something I didn't observe when I checked the codes myself on the earlier occurrences. Note, I never reset any codes, I left every code in place to either reset itself or stick around. He did a vacuum leak test and found leaks in both valve cover pressure regulating gaskets. He replaced them and I haven't had the problem since. I've refueled 2-3 times since the repair and also have been through the car wash several times. I hope it's fixed.

550sport87

1st, I disagree, water in electronics may not always be an immediate issue. I've pulled many connectors out with water in them and there wasn't even an issue. I've seen modules submerged in water with strangely no present issue. The issues typically arise when the corrosion from water intrusion begins to create connection issues
2nd. Never, never put anything your gas tank except premium fuel. I feel it's simply coincidence based off your symptoms.
3rd. I would strongly suggest putting a fuel pressure gauge on your car and check where your reading. If you have a hole big enough to allow enough water into the fuel system to make your car run poor, your check engine light would be on with some kind of evap code. If you check engine light is on, that's a great place to start. :-)