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fritzef, ASE Certified Technician
Category: GM
Satisfied Customers: 845
Experience:  ASE Master Technician
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2003 Buick LeSabre: intermittent rough idle, the hesitation..accel

Customer Question

I have a 2003 Buick LeSabre. It has intermittent rough idle, the hesitation during accel. and if I keep at it, it will eventually take off like a rocket, run sort of OK for a while, then start it again. On highway above 70 problem is less likely, but sometimes will bog down.
Check Engine Soon light comes on, then will go off the next day. Have had O2 sensor and TPS changed in last 2 wks. After the O2 sensor was replaced, it ran great for 4 days and over 300 miles and passed the emission test in Texas for an inspection sticker. Not it is acting up again and replacing the throttle position sensor didn't help. The shop that replaced the O2 sensor (which apparently wasn't the problem) wants to replace the car's computer for another $600. Do you have any better ideas? Thanks.
Submitted: 4 years ago.
Category: GM
Expert:  fritzef replied 4 years ago.
Hi, do you know what the code(s) were to lead the shop to replace the o2 sensor? Let me know and i will try to help you out. Thanks, Eric
Customer: replied 4 years ago.

They were P0122, P1133 and P1635. Per Autozone, they mean

Throttle Position sensor open or shorted internally, or bad connector / connection to sensor

Failed HO2S11 heater circuit; HO2S-11 signal shorted to ECM ground; Check sensor connector to wires

ECM has detected a fault in the 5 volt reference voltage line; sensor using 5 volt reference line shorted to ground; circuit short to ground


I drove it 150 miles this morning. Drove great the first 45 miles, then at 70 mph, would loose speed, then accellerate quickly, sometimes downshifting to get back to speed, the repeat. When I arrived at first stop and turned off for 45 minutes, it then ran fine for about 30 minutes, then did it again, but got to the point where no matter how much I put on the gas, it would not go - but engine never died. At a stop sign, the engine would lope like running on 4-5 cylinders, then when light changed, pressed on gas, but car would not go and RPMs stayed near idle. I found if I turned off the car at a light, then started it when the light changed to green, it would run fine for a block or two, then started it all again. After my second stop of about 30 minutes, it started right up and ran fine for the 50 mile trip back home.

Customer: replied 4 years ago.
Relist: No answer yet.
I received a request for more detail, but no answer.
Expert:  fritzef replied 4 years ago.
HI, sorry for the delay, my email never showed you replied. What engine do you have? the 3.8 or the 3.4? As far as the oxygen sensor codes, you may have a frayed wire that is intermittently grounding out and causing that problem. Judging from what you are describing you may be having a problem with the Mass Airflow Sensor. It is located in the duct work, between air filter housing and throttle body on the 3.4 engine. Now on the 3.8 engine is is mounted on top of the throttle body assembly. It will cause stumbling problems, loss of power, etc. It may or may not set a code.
Customer: replied 4 years ago.
The 2003 LaSabre Limited has a 3800 Series II engine. The Mass Air Sensor is in the ductwork and has been tested twice. I suspected there might be a frayed wire that can not be seen, so every connector to every sensor was unplugged and the wiring carefully inspected with nothing visible. Is there no common sympton that leads to a solution, or is this one of those "change out everything" and hope for a miracle deals?
Expert:  fritzef replied 4 years ago.
How was the sensor tested? Mass airflow sensors are very sensitive and critical to proper operation of the engine. They measure how much air is entering the engine and the computer makes calculations based on the info from that sensor, along with other sensors. They are hard to test. But if the wrong airflow readings are sent to the pcm, it changes, timing, fuel, etc and can cause major drivability issues. One easy thing you can try is with the engine running abour 2000 rpm, lightly tap on the sensor and see if the engine stumbles, or does anything abnormal, If so, then the sensor is your problem. Also look real close at the terminals in the connector to the sensor, If any of them look spread out this can also cause intermittent problems. Let me know what you find. Thanks, Eric
fritzef, ASE Certified Technician
Category: GM
Satisfied Customers: 845
Experience: ASE Master Technician
fritzef and 3 other GM Specialists are ready to help you
Customer: replied 4 years ago.


Changed MAS, so now have changed out O2, TPS and MAS and the problems are exactly the same, but there is something peculiar that may help and I'm sure I've mentioned before. After changing out the TPS, it ran great for about 3 hours and then on a trip of 50 miles. During that time and after a few stops, the check engine soon light went off. Then, on the trip back, it began acting up exactly as before and by the time I got home, I had to turn the engine off each time I got to a light. When the light changed, I'd start it up and it would run fine for a minute or two, then start it again. I then changed out the MAS and it didn't make any difference. Someone recommended changing out the computer - another few hundred dollars - but I'm not convinced it is the problem as the car always starts up and runs fine for at least 30 - 60 seconds after I turn it off and restart. When I start it on a cool and sometimes humid morning, it tends to run good for at least 30-minutes. When it's acting up, pressing on the gas has no effect except to make it try to stall out, and/or suddenly burn rubber and take off like a rocket. It will not accellerate, then take off, then bog down again and this makes for some interesting driving and stares from other drivers.

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