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2001 Century hesitation and shifting


lajaycee@cox.net
01-07-2007, 02:24 PM
Hi All,

I am new to this forum, so I apologize if I leave out something.

I have a 2001 Buick Century that I bought second hand - it had 33000 miles. The engine is the 3.1L V6, and has a 4-speed automatic.

I have been religous with oil changes and service, typically having service performed within 500 miles of listed mileage.

Currently, the car has approximately 106,000 miles.

In September 06, (97,000 mi), I noticed a slight hesitation when running at cruising speeds (70 mph). I also began to notice what I will refer to as an "occasional" hard shift. Essentially, it appeared to occur when I would et in heavy traffic only.

In October, I also began to notice that gas mileage had dropped. Instead of 32.5-33 mpg, it had dropped to 28.5 mpg.

I brought the car into my Buick delaer, with my listed observations. They performed a 100000 mi tune-up and transmission flush/check ($430.00 cost) and stated the car was in good shape.

Since then, I have brought the car back twice, for all of the same isues, and they can not find out what the problem is - they state it does not present the same problem in the shop environment. I have even gone so far as to ask for a mechanic to ride with me to demonstrate and they refuse.

Here is a rundown of my currrent observations:

1. When I start the car in the morning, the ca appears to run properly - no hesitation and shifting is smooth.

2. Usually (not always) within 20 minutes, shifting appears to become hard through all gears, with noticeable pauses between gears. Since this is my work car and I drive long distances (60 miles one way), I can not really state when it actually begins to occur. I have tested around town, but it does not always present the same.

3. I have also noticed a "high-pitch" whine seems to be present when the hard-shifting begins to occur. I can turn off the radio and hear it pretty well. I have even tried raising the hood to see if I can pinpoint a source for the noise, but can not.

4. Hesitation seems to occur on heavy acceleration - I really notice when I try to merge into bridge traffic from an on-ramp lane (attempting to go from 30-60 on an incline). I do experience hesitation at other times, but it does not seem to present on a consistent basis.

5. Gas mileage before the hesitation and shifting problems began was consistenly between 32.8-33.2 (yes, I drive like a paw-paw). ight now, the best I can "consistently" obtain is 28.5-28.8, although I have actually had wo tanks measure out at 32.5 and 32.8. Suspiciously, on both of these occasions, no hesitation and very little hard-shifting was noticed/experienced. Now, some will say that I probably did not fill the tank exactly the same every time, but I promise I have always been very exacting in gassing up, almst anal about it.

With the above listed, does anyone have any ideas on what I could check or ty>

meistermind
01-07-2007, 08:33 PM
Could try a TPS (throttle position sensor). Its cheap and easy to replace. Its located on the end of the throtle plate shaft, on the outside of the throtrtle body, opposite side from the cables and linkage. Sometimes the TPS gets a flat, or dead spot when they go bad. This is noticable as a non-responsive area of the throttle, but it will act normal as you press the accelerator past this positon. They often go bad near the lower end as you begin to accelerate up a hill to gain a little speed back, since this is the throttle positon that gets alot of use when cruising along. Alot of electronic parts act flaky as they warm up, as heat is their biggest enemy that fails them.

maxwedge
01-08-2007, 09:54 AM
Yes a " flaky" tps can cause this but certain electronic trans components can cause this also and can only be diagnosed doing a full trans scan while the condition is occurring. The high pitch whine is the tipoff here, as the trans pwm solenoid can cause this.

lajaycee@cox.net
01-08-2007, 03:29 PM
Meistermind and maxwedge-

Thank you so much for the quick response. I will look into both of these tips.

Lajaycee

Skaricavision
04-13-2009, 02:10 PM
Forum,

Similar probs.....1998 Buick Century, 3100 V6, 4T60E transmission, 120,000 miles....

1) When cold, shifts perfect

2) When warmed up, no hard shifts, but great hesitation, especially with light acceleration - especially from a stop - no power, great hesitation

3) Overdrive "punky" - in and out and un-predictable - only when warm

------------- What did I do ? changed the TPS sensor and everything is great now - like night and day !!!!!!!!

Give this a try first........

Good Luck !

It is a low cost, first try...........

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