Hi all,

I need help with diagnosing this unique problem with my car. I have an '09 E-350 with 75K miles now. Always dealer serviced and maintained. Car is a daily driver and I drive about 20 miles daily. Occasionally use it for weekend trips as well.

About 3 months ago, drove to San Antonio and before reaching there CEL came on. I went to Autozone to have the codes read and it said P0300, P0302 and P0304. I had the car serviced for 70K miles, scheduled service, before the trip (less than 100 miles) and at the time they said get ready for spark plugs on next service. SO i thought I'll change the plugs and see what it'll do. The CEL went off BEFORE i could change plugs but I did it any way. On the trip back, it came back on. I kept driving and put in a can of techron. CEL went off after a while. Came back on in a little while and then off again. All this time the car didn't give any other problems and kept running smoothly. I drove more than 200 miles like this and reached back home. Parked it for 3-4 days and had a look again. Changed spark plugs AGAIN - same result. Shuffled the coils on the two cylinders and read codes using my own laptop and software and same result. Kept driving the car with the CEL on/off intermittently. Since the plugs, coils and wires checked out I am now thinking if it can be injectors. (Tested injectors using screw driver test - and they all work fine).

Now the problem is, the engine doesn't run smoothly when there is about 2 bars of gas left in the car or if I fill up the tank. If i fill up, it will start idling roughly, hesitating at low speeds (less then 15 mph) but as soon as it has used 1/4 of tank OR i put in fuel system cleaner it starts running great and doesn't hesitate or idle rough. The CEL comes on as soon as I fill up the tank and goes off when I use fuel system cleaner. I read the codes and they are the same P0300 P0302 and P0304 when CEL is on. No other codes are thrown/pending etc.

I need to have this diagnosed and I don't want to go to the dealers. Any suggestions?

Plz note, I've changed plugs twice (2nd set bought from dealer), changed MAF, switched around coils to check if any of them was bad and looked for leaks as best as I could. But I can't figure out why it runs smoothly for less than a full tank of gas and will not throw codes but will throw codes if I fill up the tank or am running real low on gas and its the same codes always.

Thank You.