difuria

I've had a performance issue with my ES300 for a few years. The car has 130,000 miles and is in great mechanical condition. My mechanic hasn't been able to nail down the exact cause. The issue can be intermittent and isn't noticeable to others who don't have a history of driving the car.

The car continues to throw check engine codes PO442 and PO456. The gas cap has been replaced, vacuum hose replaced, a tuneup recently performed, the purge valve was replaced last week by my mechanic. After replacing the purge valve the car ran great for a week, until the code threw again. Any suggestions on what may be throwing these codes?

Also, it's hard to determine if related to the codes, but when the code throws the car seems to get the sluggish symptoms. I notice a loss of power at idle and high speeds. I have to push the gas pedal harder to make it accelerate or keep it at freeway speeds. Additionally, when at freeway speeds the car will suddenly lose power and speed. It feels like the cruise control is on when you go downhill, but this happens on a level road with the cruise control off.

When the car is sluggish, you can really notice it when the AC cycles on and off. There's a clunk, and greater loss of power. The transmission doesn't shift as well, the idle is noticeably rougher, the car almost feels like there's a miss at high speeds..almost a pulling surging feeling. It feels like it really struggles to go.

When the purge valve was replaced last week, I only had to feather the gas pedal to make the car go. There was lots of power at acceleration, didn't notice the AC cycling on and off, the car coasted better, and the idle was still rough but not as rough. The car ran great like it did a few years ago.

Any ideas is greatly appreciated.

Brian

HomerJay

What did the "tuneup" entail?
If it did not include cleaning the throttle body, that would be a recommended first step. Also try using a high quality fuel system cleaner like Chevron Techron.

difuria

The tune up included plugs only. I have cleaned the throttle body a couple times over the past few years. The first it was really dirty, the second time it was pretty clean. Both times it didn’t help with the symptoms above. I’ll give the Techron a try.

thanks.

Arsenii

Hello,

Did you install OEM gas cap?
Which vacuum hose was replaced?

See if the filler neck is good, then check all the the EVAP tubes and hoses (even the ones under the hood) for cracks, looseness, or any other sign of leak. Sometimes, vacuum switching valves can get stuck in the opened position, to check if it is still operable, blow air into it and apply 12V, see if that will change anything. You can also check if your Pressure Sensor works properly - with the key in the ON position, check if 5V and Ground are coming to it, and then check its output with 5V applied to the sensor. With no vacuum (all the hoses disconnected), there should be from 2.9V to 3.7V, when 4kPa of vacuum are applied, you should see 0.5V or less. If none of that will yield any results, some advanced scan tools (like MiniVCI cable) have an EVAP leak detection mode, and if there is a leak, you will probably have to do an EVAP smoke test for further investigation.

From my understanding, for every DTC in the car, there is a Fail-Safe mode. For example - if the knock sensor malfunction is detected, the ECU will advance ignition as much as possible, and will not allow O/D to engage. My theory is that it is the reason why your car's performance drops each time CEL appears.

Hope this helps and best of luck!

difuria

Thanks for the detailed response. I'll start testing the switches you mentioned. The gas cap is OEM. I've tried both aftermarket and OEM. Not sure on the exact vacuum hoses changed, but numerous have been over the past year or so. There's a ton under the hood. I know the ones that were hard and cracked were replaced.

Arsenii

Not all the vacuum hoses have any relation to the EVAP system. Under the hood, there are two EVAP lines - the one that goes to the CCV solenoid on the air box, and the one with service port, going to the EVAP solenoid located on the valve set. Even if other hoses that are not related to EVAP system are leaking, it will mess up the performance of the car, but it will not compromise EVAP system tightness. That said, there is a whole bunch more hoses to worry about under the vehicle, around the charcoal canister and fuel tank. Below are a couple of links that that should help you guide through there:

check engine code PO 440 PO 446
rx300 code P0440 what do I check?

Hope this helps and best of luck!

Oro

There is also a vent valve on the charcoal canister that fails eventually, contributes to these codes.