Car stalls/dies when tank is half and turning right


Can anyone diagnose this issue.

2004 civic ex with over 300,000 miles

For last 5 months or so, I have to keep full tank of gas. If the tank is half, the car starts stalling, and the first sign of it is when I am taking a sharp right turn on highway exit. It’s like the engine dies for a second or two and comes back when the right turn is over. If I keep driving and the tanks get lower, it will happen even without the right turn. I just fill up the tank and the problem is fixed.

Check engine light is on sometimes (but not always) with these codes P0171B and P0497, but I am not sure it’s related.

There is sometime also a short delay in starting the car, irrelevant if the tank is full, (a second or two of extra cranking) but that might be a different issue too.

It sounds like an evap problem. Have you tried to loosen the gas cap when this happens? Fuel pump may also be weak. That can be tested with a fuel pressure gauge. The P0497 is for the purge valve on the evap canister or a hose to the purge valve. I would replace the purge valve.
THe P0171 is probably the O2 sensor.

I forgot to mention that I did replace fuel pump. That didn’t fix it.

Try changing the fuel pump relay.
The symptoms don’t really match, but that relay is a common failure on Hondas.

When you fill the tank when the gas gauge reads half full how many gallons does it take?

MY 2 CENTS has a good point. If you have the manual see what the fuel tank should hold and check your fuel mileage. With luck it might show the gauge is not correct and you are just lower on fuel than you think.

When it’s half full it takes probably 8 gallons. If it’s empty, it takes around 14

What I don’t understand is why the symptoms start appearing when turning right (not left) and the problem disappears when the tank is full. It’s like something is unplugging when taking right turn, but if that was the case, why full tank will fix that.

Have you loosened the gas cap yet to see if the symptoms go away?

I did take off gas cap and put it back again (tightly). Loosened? No, I guess haven’t tried that.

Tried it and no loose gas cap doesn’t make a difference.

Ray and the Late Tom had a caller on Car Talk with a similar problem recently, and they said it was oil getting into the valve guides, and turning that particular direction tended to cause the oil to run towards the valve guides in that car’s engine.

But I don’t think oil in the valve guides is causing your problem OP. But it has to be something like that where centrifugal force is causing something or another to change in the engine’s fuel delivery system. If you could measure the rail fuel pressure while driving, you’d probably notice it is dropping like crazy when you turn that direction. Possible causes, given the fuel tank filling relationship

  • Weak fuel pump
  • Pinched fuel line
  • Evap system developing a vacuum, preventing fuel delivery

First thing to try, see if it goes away with the gas cap loose. If so, you know it is an evap problem. If nothing found there, time to hook up a fuel pressure gauge.

First thing to try is loose gas cap===OP did that already.