Cel / Engine Acting Strange

[champion4206901]

I HAVE A 2001 IS300 AND MY CEL IS ON. CODES READ ARE P0171 AND P0174.... IM GETTING HORRIBLE GAS MILEAGE AND ALSO WHEN EVER I TRY TO STOMP ON THE GAS OR TRY A JACKRABBIT TAKE-OFF MY CAR HESITATES AND AND DOESNT TAKE OFF. INSTEAD IT FEELS LIKE ITS CHOCKING AND DROPS IN RPM'S. IF I KEEP MY FOOT DOWN ON THE GAS IT'LL CONTINUE LIKE THIS AND NOT PICK UP ANY SPEED. ALSO, IF IM IDLING AND I FLOOR IT OR HALF-WAY FLOOR IT. THE ENGINE WILL DOUBLE REV. FROM 1000 RPM IT'LL GO TO 2500 RPM, DROP TO 1000 RPM THEN GO UP AGAIN. PLEASE HELP ME OUT HERE. ALSO IF THIS HELPS... I JUST, LIKE 1 WEEK AGO, CHANGED MY SPARK PLUGS. I HAVE AN AEM SHORT RAM INTAKE BUT THIS WHOLE THING HAPPENED EVEN WHEN I HAD THE STOCK INTAKE. THANKS IN ADVANCE.

[lenore]

P0171 is fuel injection system fuel trim too lean bank 1

p0174 is fuel injection system fuel trim too lean bank 2

I suspect your ecm is reading the pre cat Oxygen sensor incorrectly and compensating . I would look at the pre cat oxygen sensor and see if it has a broken wire. Maybe somebody else can dial this in. the only other thought is the IAC is stuck partially open and causing maximum air. I know I have seen those codes and it relates to the Oxygen sensors. Yup I looked elsewhere and it is probably a bad IAC valve sticking.

[smooth1]

I actually answered this for you in the IS 300 forum already. No need to post in all the forums.