Flipper1

I think my mom's RX is suffering from a flooded evap canister. For a while now she has complained about getting bad gas from a local station. It runs bad for a little while and then clears up. Well, this past weekend she asked me to look at it. The car stumbled a lot and did not really want to rev.

After reading a couple of posts on Lexus forums, I thought it was bad coils. So I swapped in a new set of coils and plugs. It still ran like crap.

I drove to autozone and had the pending codes read. There were three. 1 for lean, 1 for AF sensor out of range, and 1 for AF sensor heater not working. My dad had previously cleaned the mass air sensor, but it did not seem to help. I bought a different mass air and installed it. The car drove great. We put 150 miles on it and it seemed to act like new. I thought it was fixed. ...then I filled the tank up and the running like crap condition came back. (when I first started messing with the car, the tank was also full).

I think gas is overflowing into the canister. When the canister fumes are supposed to be going to the engine...liquid fuel is being sucked in...which is fouling the plugs and washing down the O2 sensors.

What is the real defective condition? is it something wrong with the canister? or the check valve on the gas tank?

carguy07

I would try running at 1/2 tank max for a while and see what happens. Never heard of a canister doing anything like that before.

maxSteel

Did the CEL light up before it started "running like crap"? You might just be experiencing the "limp mode" it goes into for some codes.

Flipper1

The original check engine lights were cleared by dad before I got involved. After the refuel the trac control lit and the check engine flashed.

Flipper1

The fuel level shut off valve 77390-48010 seems like the most logical cause for a flooded canister. I'm gonna try replacing that first.

maxSteel

What was the first code reported?

Is there fuel in the vent line hose?

Flipper1

First code reported by autozone was P0171
The second was maybe P0134 (the printout is still at mom's house....250 miles away). The third was maybe P0135.

I did not tear into it. I was pissed. I will tear into it this weekend.

I did however find a similar thread on a forum that described a similar car that somebody fought for a long time that the issue turned out to be the canister.

On a related note....there are vehicles that do have known problems with the canisters flooding (chevy malibu, and chyrsler mini-van to name two) that do have driveability demons unleashed when the canister floods.

maxSteel

P0171 "system too lean bank 1" trouble areas are:

• Air intake (hose loose)
• Fuel line pressure
• Injector blockage
• Oxygen sensor malfunction
• Air flow meter
• Water temp. sensor

Unless if the gas tank vent line has liquid gas in it I don't see how the canister could be flooded.

Flipper1

My guess is that the main tank vent is not completely sealing off. ...and at a full tank, some fuel is seeping into the vent hose.

When the issue occurs, this thing runs SO BAD! ...as if it is sparking on less than half the cylinders. Big doses of raw fuel would probably confuse the hell out of the O2 sensors (lower combustion temps) and it doesn't know how to properly diagnose the data.

I will know tomorrow.

Flipper1

I went ahead and bought a 77390-48010 tank vent valve. The plan is to drain/drop the tank, swap the valve, drain the canister, and re-test.

According to my mother, the running like crap after re-fueling, has happened something like 20 times. ...she just finally made a big enough of an issue about it for my dad to investigate (and get me involved).

Once she has burned 1/8th tank of gas (her normal run to the mall?), it runs like new.

maxSteel

That sounds more like a too-rich condition, which is P0172

Many of the trouble codes will put the engine in "limp home mode". It runs rough, has no power, won't shift into overdrive. It's normal behavior.
I don't have a list of the codes that will do it.

If you clear the codes (and they don't come back immediately, some must go through a cycle) is the performance restored?

Flipper1

Clearing the codes did not help the run like crap condition after fueling. The light came back on quickly.

Between 3/4 and 1/2 tank, the light stayed off.

fastnoypi

if you did have a p0135, it is a o2 heater malfunction. the o2 can't give feedback to the ecu to compensate for fuel trims.

RX469

iTrader: (1)

Waiting for your update on this issue...

Good luck!

Flipper1

I will let you know. I am anxious to see what fixes it too.