02 Monte ss Stutter when shifting

I appreciate any and all help as I am not knowledgable about cars in any sense.

I have an 2002 Monte Carlo SS that has been regularly serviced and taken care of very well. It has had no major work in the four years I've owned it, or even before (Had a total of two owners, including myself), the only work being a replacement crankshaft sensor. The problem:

Around two weeks ago I noticed when I increase the throttle, such as merging on a highway, the car will stutter/lag usually at around 3000 rpm @60 mph. What I mean is, while accelerating, the car has a hard time shifting and will just hover at the top without shifting over, and I can hear the engine sort of struggling. However, this does not happen any other time and will not happen if I ease the gas, only when I accelerate and hit around 3k rpm will it do this. It does not "hard-shift" it will just stutter and I'll have to ease off the gas in order for it to shift.

Other than this problem, the car is perfect. Just this one hang-up. No problems idling, oil, air-filter, temps, are all fine. The car does sit 4 days a week usually and I only put the cheapest gas in it.

Could this be a problem with the throttle? Dirty fuel injectors? I remember a re-call on catalyst for the monte carlo's a couple years back, could this be it? I have not taken it to the dealer as of yet, so No codes.

Any and all help is greatly appreciated. I will answer any further questions promptly, thanks in advance.

Welcome to AF, many things can cause this, restricted fuel filter, general tune issues, a clogged cat, internal electrical trans issues, someone should drive the car and/or do a full scan for a proper onsite diagnosis.

Thanks for the reply, I guess my best bet would be to take it to the dealer and get a diagnosis. Probably should have done that in the first place.

You may also want, if the vehicle hasn't gotten over 120,000 miles, to have a chevy dealer check the cat converter for blockage. I went through that with mine and, as long as it's below the 120,000 miles, chevy should do it free of charge. There's a Chevy service letter running around:

Condition
Some customers of 2001-02 Chevrolet Impala, Monte Carlo; Pontiac Grand Prix; and Buick Regal model vehicles, equipped with a 3.4L (RPO LA1 - VIN E) or 3.8L (RPO L36 - VIN K) V6 engine, may experience a condition where the vehicle exhaust catalytic converter is replaced due to complaints of lack of power or illumination of the Malfunction Indicator Lamp (MIL). This may be due to the front endcone insulation from the catalytic converter breaking away and blocking the front of the first catalyst brick and preventing the free flow of exhaust gas through the converter.
Special Policy Adjustment
This special policy covers the condition described above for a period of 10 years or 120,000 miles (190,000 km), whichever occurs first, from the date the vehicle was originally placed in service, regardless of ownership. The repairs will be made at no charge to the customer.


Check it out!