99 Es300 Dies With P0171 Error Code

[way2007]

Hello,

i have a 99 es300 with 148k miles and recently got engine lights on with error code P0171. This also happend a year ago where i replaced the o2 sensor and the error went away only to resurface after a year.

couple months ago i observed a hissing or some similar sound while driving and when i opened the hood i could hear it somewhere close to the belt near the engine when the car was on. I wasnt sure what was causing it.but now when i turn on the car and try to listen closely i am not sure if i hear it again or if its continously doing it..

Also when i start the car for the first stime it would die. but when i start the second time with my leg on gas raising the accelerator the car would start fine.this happens frequently.

I have also observed a slight sound from the engine side (not sure what i should call it sounds like garr...)when i accelerate the gas after a stop sign. this goes off on a increasing speed. only happens when i put my legs on the gas after a stop or from a slow speed to increase the speed.

Anyone have any thoughts what i should be looking at ..or what could be causing these symptoms. Is there a diy steps to look at air/vacuum leaks/replace fuel filter etc? i did the o2 sensor replacement myself last time so would like to do the troubleshooting if its doable .

thanks again in advance

[camlex]

How many O2 replaced? if answer is one, times for another.

also times for cleaning TB, IACV.

Check dogbone mount on top by passenger side.

[George_Jetson]

Yes definatly check the dogbone mount, the noise could be a vac leak due bad hose (as engine move, the hose also moves). So of course you also want to check hoses. Which sensor have you already replaced? I would normally recomend replacing both of the 1st sensors at the same time (bank1 sensor 1 and bank 2 sensor 1).

You can get a visual on how much the dogbone is moving by opening the hood, and STAND OFF TO THE SIDE OF THE CAR. Have a friend place the car in drive, and WHILE HOLDING THE BRAKE DOWN, give the engine a little bit of gas. The engine will move, you should see the dogbone move also.

Of course have the car parked in a spot where it is safe, in case it moves a little. Also stand off to the side for the same reason.

[kashi125]

Out of curiosity, what does a dogbone mount do and if its rubber is cracked, what symptoms would it cause?

[George_Jetson]

The dogbone mount helps control the engine torque, if it is worn, the engine will rotate along it's axis when torque is applied. This can cause several problems, such as the rubber hose connecting the throttle body to the MAF meter will flex more than it should (if it is old and cracked it will open leaks), the axle CV joints will be placed at angles that they were not intended to, for just a couple things. This is a issue with rubber engine mounts that is not isolated to transverse engines, longitudale mounted engines also have these issues, but the symptoms are different.