Lexus Troubleshooting Questions? Ask a Lexus Expert
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Does the engine misfire at idle or when driving?
Has any repairs been done underhood recently?
The codes P0171 (system lean bank1), P0174 (system lean bank2), p0330 (knock sensor), P0776 (shift solenoid B performance). Out of all these codes P0171 and p0174 can make the engine run rough at idle. Need to start by checking for vacuum leaks underhood.
Since both the banks are affected check main air hose to the throttle body for cracks, booster vacuum hose and also aroung intake manifold area. IF no vacuum leaks found then next step is to check the fuel pressure.
Hello, just checking if any updates?
If no more vacuum leaks are present then check the fuel pressure. Need to make sure that is with in specifications before you start driving.
On this vehicle the manufacture has not provided a fuel tester port. The fuel pressure will need to be tested at the fuel pressure line with help of a closed fittig and fuel pressure gauge. The pressure is supposed to be 44-50 psi.