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Cel / Engine Acting Strange


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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.

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Hello, and welcome to the LOC.

Alright. Let's break this code down for you. P0171 and P0174 is a bank 1 and bank 2 "Too lean A/F mix" read cel. This can be from :

1) Air intake issue

2) Bad fuel injectors or fuel injector clogged

3) fuel pressure issue

4) An open or heated 02 sensor

5) PCV Piping issue

6) ECM error

Right now some of the symptoms you are describing are partly due to the ECU trying to account for the lean issue by retarding the timing and dumping more fuel. So disregard the poor fuel mileage as a symptom, and choking and RPM droppage. That's the ECU trying to help prevent damage.

So, with out the car to do a full diagnostic and track down the lean condition cause, you will have to either 1, take it in and have a mechanic figure out which one of the things I listed here are causing the condition. In most cases it's just a bad 02 sensor. But you seem to have a strong acceleration issue that most of the time indicates a fuel injector problem as well. Which is what I think you issue is. BTW, try not to step on it until you have this resolved, lean conditions are really really bad for the pistons.

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Can also be a sticking or bad IAC valve and sensor.

the problem I generally see with the IAC is when your are cruising at speed, then slow down to stop and the car will just die. That is what would lead me to think the IAC valve. In this case they talk about having an acceleration problem, that and the Lean condition cel would lead me to beleive it's a fuel injector issue, or fuel pressure related problem. If they had no issues and had the cel, I would think it was a faulty sensor, and if the car had idle issues and trouble at most speeds, then I would think it was an air intake issue, or PCV piping issue.

What do you think?

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