ES300 stutters. CEL code P0171. Need advice

[tomf]

Help. I bought a 99 ES300 last Jan. Now the check engine light is on. Also the vsc and vsc off are on. AutoZone found the following codes: P0171 and P1133. Both indicate some sort of malfunction at bank 1 sensor 1. Additionally when I'm cruising along with my foot lightly on the accelerator the car stutters. I cleaned the MAF sensor. It was dirty. After cleaning the MAF sensor the stuttering was more pronounced and frequent. I'm thinking I need to replace the O2 sensor. I've read other threads with P0170 error code but none with stuttering. Any advice would be appreciated. Thanks in advance Tom

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[angmedic91]

Originally Posted by tomf

Help. I bought a 99 ES300 last Jan. Now the check engine light is on. Also the vsc and vsc off are on. AutoZone found the following codes: P0171 and P1133. Both indicate some sort of malfunction at bank 1 sensor 1. Additionally when I'm cruising along with my foot lightly on the accelerator the car stutters.

I cleaned the MAF sensor. It was dirty. After cleaning the MAF sensor the stuttering was more pronounced and frequent.

I'm thinking I need to replace the O2 sensor. I've read other threads with P0170 error code but none with stuttering. Any advice would be appreciated. Thanks in advance Tom

A P0171 is related to the MAF sensor, needs to be cleaned out and I would recommend resetting the ECU, so the unit resets with a clean MAF, otherwise you might need to get a new MAF sensor. I recently had a P0171 and had the dealer clean it out and still got the code again, then I read on here, that after several attempts to clean, you might want to get a new MAF sensor. Anyways, I bought a new MAF and noticed right away that the car idled better and didnt have as much vacuum thru the air intake. Before I had a loud vacuum sound thru the intake on cold start up, high RPM, but now with the new MAF sensor, the loud vacuum on cold start up is gone and the RPM's are not as high. Im not familiar with your other code. Good luck.

[dcapo]

got the same problem with the p0171 , gonna redo my exhaust tomorrow and change the o2 sensor by the cat, also installing more new plugs, so ill see how it goes

[angmedic91]

Originally Posted by dcapo

got the same problem with the p0171 , gonna redo my exhaust tomorrow and change the o2 sensor by the cat, also installing more new plugs, so ill see how it goes

P0171 is a MAF sensor issue. Do you have an aftermarket intake system or wet type filter system (K&N)? I was told the wet type intake system wreck havoc on our MAF sensors. I would recommend cleaning it and reset your ECU. I had the same issue and cleaned it several times, so now I just recently bought a new MAF sensor, so far so good.

[dcapo]

Originally Posted by angmedic91

P0171 is a MAF sensor issue. Do you have an aftermarket intake system or wet type filter system (K&N)? I was told the wet type intake system wreck havoc on our MAF sensors. I would recommend cleaning it and reset your ECU. I had the same issue and cleaned it several times, so now I just recently bought a new MAF sensor, so far so good.

yeh i do have the short ram (no reoil) intake, but i switched back to stock and same results, also got another maf at the junk yard from same gen(1st find for that gen ever, think it was 99) i also switched out the rear valve cover due to stripped bolt on one of the plugs, but only thing was different was the pcv valve was aluminum screw on? could be my problem? cleaned my both my mafs w/rubbing alcohol once again today
i did mess with the throttle position cable too

pic of pcv valve location and 4ga upgraded ground wire

[tomf]

I've been trying to troubleshoot my car's problem. Things I tried are: Cleaning the MAS, adding fuel injector cleaner, and searching for vacuum line leaks. Finally the Stuttering/Jerking/bucking got so bad I broke down and replaced the MAS.

It's been 3 days and no Stuttering/Jerking/bucking but I still get the VSC and VSC OFF lights periodically, usually after about 3 or 4 minutes driving from a cold start. I'm wondering if this might be an indication of a failing air/fuel sensor. I read somewhere that unheated O2 sensors take several minutes to warm up before being they will generate a voltage signal. During his warm up phase, the fuel feedback control system remains in "open loop" and does not use the O2 sensor signal to adjust the fuel mixture. Could it be that once the sensor is warmed up it generates faulty signals leading to the error lights and the Stuttering/Jerking/bucking? Anyone have any thoughts on this theory.

Before replacing the MAS, the VSC and the VSC off lights would come on after 3 or 4 minutes. Then the check engine light (CEL) would come and the Stuttering/Jerking/bucking would start.

I have a OBD II scanner due tomorrow that should help me diagnosis this problem.

I'm not convinced I've solved the Stuttering/Jerking/bucking problem because its' only been three days.

Thanks in advance for your advice and input. Tom

[BostonEs3]

checked your coils?

[tomf]

It's been a week since I've replaced the MAF sensor. No stuttering since replacing it. Four days since I've seen the VSC and VSC off lights. It's looking more likely the problem was the MAF sensor. I'll report back if I get any more error lights. Thanks Tom

[tomf]

Yesterday the VSC, VSC OFF and CEL returned. I used by new OBD II scanner and got the same codes; P1133 and P0171. Also read the freeze fame data:

SHRTF1(%) 19.5
LONGFT1(%) 24.2
SHRTFT2(%) 10.9
LONGFT2(%) 3.1

So today I'm replacing my Air and Fuel Ratio Sensor with a Denso 234-9007.

I'm just waiting for UPS to deliver it so I can install it. I've attached a picture of the old air and fuel sensor.

[angmedic91]

I would suggest you buy a new OEM MAF sensor for your P0171 code. I had that same issue and cleaned it many times and didnt help, so I bought an OEM one off of ebay for $120.00 and have not had an issue with a CEL for P0171.

[tomf]

Originally Posted by angmedic91

I would suggest you buy a new OEM MAF sensor for your P0171 code. I had that same issue and cleaned it many times and didnt help, so I bought an OEM one off of ebay for $120.00 and have not had an issue with a CEL for P0171.

See post #8. Replaced it about a week ago. I thought my problem was fixed until yesterday.

[tomf]

It's been 2.5 weeks since I've changed the air fuel ratio sensor. No more stuttering. The VSC and VSC off lights came on twice which went away the next time I started the engine. Once I read the OBD II data which indicated a pending problem with the downstream oxygen sensor (P0136, if I remember correctly). Looks like eventually I'll have to replace the downstream O2 sensor. I'll wait until the check engine like comes on and stays on.

It appears my initial problem (P0171) was with the bank 1, sensor 1 air fuel ratio sensor. I'll update if any related problems appear.

[angmedic91]

Thanks for keeping us updated on your issue.