water in gas tank

[jowens]

We have a 2002 Subaru Legacy Outback. We are wondering if it has water in the gas tank. The check engine light is on. What the car is doing is ever so often the engine hiccups and then continues without interruption. It is nothing consistent. It doesn't do it all the time. We took it to Auto Zone to check the engine code and it comes up code PO304. Mechanic recommended putting in E85 gasoline to remove the water if that is what it is. Fuel filter was checked to see if water was in it. No water was found. New fuel filter was installed. We have put STP gas treatment and Lucas gas treatment in it. This all occurred after having filled up with gasoline at a service station taken over under new management. Any suggestions will be greatly appreciated.

 

Thanks,

Jo

[OB99W]

P0304 is "Cylinder 4 Misfire Detected". If that's the only code, it's hard to tell if gas quality is an issue; since there apparently aren't codes for the other cylinders, it might be less likely.

 

Does the problem seem related to the tank level (is the problem any more or less evident at full or near-empty)? Does it show up any more frequently going up/down hills or on curves?

 

How many miles are on the car? When was the most recent tuneup done (replacement of spark plugs, possibly ignition wires, etc.)?

[jowens]

P0304 is "Cylinder 4 Misfire Detected". If that's the only code, it's hard to tell if gas quality is an issue; since there apparently aren't codes for the other cylinders, it might be less likely.

 

Does the problem seem related to the tank level (is the problem any more or less evident at full or near-empty)? Does it show up any more frequently going up/down hills or on curves?

 

How many miles are on the car? When was the most recent tuneup done (replacement of spark plugs, possibly ignition wires, etc.)?

 

The problem is more prevalent at low tank level. It shows up more frequently going up hills. There is 78,000 miles on the car. The most recent tune up was done at around 56,000.

[northguy]

Try Heet.

[Equalizer]

Hi Jo,

 

I used to get this problem a LOT in an old GL. Even got to the point where I had to spend a couple hours, with an empty tank, draining the bottom of the tank of well over a quart of water. After this, I just got my gas from a different station that had a good reputation and added Dry Gas every couple of tank fulls. The only kind that I found that worked at removing h2o contained ISOPROPEL alcohol. The methanol stuff was cheaper, but just a waist of money. This time of year was always a problem, partly because of condensation because of changes in temp. At least that's my theory.

 

That said, the car at that time had a 1.8 engine. Our newer 2.5 leg OBs have air tite gas caps and bigger engines. I never had a condensation problem with my OBs, albeit bad gas is bad gas and could cause the same problem. I don't know about the code. But if you use an additive, just make sure that the ingredients are isoprople and not methanol.

 

Hope you get your OB back to normal.

 

eq

[nipper]

When you say the car had a tune up, exactly what was done?

 

This is not bad gas, as bad gas would be all cylinders, and it wouldnt necassarily be picked up by the ECU.

 

nipper

[Cougar]

I recommend you change out the sparkplug and plugwire for #4 to see if that will correct the problem.

[OB99W]

The problem is more prevalent at low tank level. It shows up more frequently going up hills. There is 78,000 miles on the car. The most recent tune up was done at around 56,000.

There could be more than one problem. Since the symptom is more prevalent with a low tank and going uphill, there may be contamination of the gas by water, or even possibly by some debris; however, many cars have at least some tendency to misfire when the tank is very low. Furthermore, since cylinder #4 is misfiring while the others apparently aren't, there may well be issues with the #4 ignition and/or fuel injection that make it more sensitive to fuel quality or delivery. It's also possible that the problem has no relationship to the newly managed gas station, and coincidentally cylinder #4 began misfiring for another reason.

 

If you believe there's water in the gas tank, adding some anhydrous ("dry") alcohol might help. E85 contains a very high percentage of alcohol (ethanol up to 85%), and you have to be careful not to add too much of it to your tank. While some have said they have no problem using up to 50% E85 mixed with 50% "pure" gasoline, Subaru suggests not exceeding 15% alcohol. You could just add a "drygas" product instead. Don't use "rubbing alcohol" from the drugstore; it's almost always 70% isopropanol, but the remaining 30% is water.

 

If the alcohol doesn't do the trick, it's probably time to investigate the #4 spark plug, etc. You also should verify that P0304 is the only code.

[nipper]

I was thinking fuel filter myself.

 

nipper

[OB99W]

I was thinking fuel filter myself.

Could be; jowens said the fuel filter was replaced, but if there's debris, it could be partially obstructed again.

[nipper]

Could be; jowens said the fuel filter was replaced, but if there's debris, it could be partially obstructed again.

 

OR a poor quality filter.

 

There are a few other suspects. One thing to look at is the evap system to make sure its operating properly. Another is to have a fuel pressure gauge put on the car and monitor whats going on. Another suspect is the fuel pressure regulator (and a more likely culprit).

 

nipper