02 Grand Prix Hesitation

You might want to run a compression check and see if it's within spec. While it might not generate a code, an engine with wear on it might be getting weak enough to require the downshifting and the cough you mentioned. You might also put a pressure gauge on the fuel rail and check that your pump is up to snuff. Another thing to look into would be the miles of vacuum lines. An open vacuum source can cause all kind of gremlins to poke thier heads out.

I have the same car, had a similar problem. turned out to be a clogged Catalytic converter, at 70k. it was still under the smog warrenty.

Does your check engine light come on also. Mine came on last week and onstar diagnosed it and said it was a loose fuel cap. Was not sure if this was related to the catalytic converter.

Hello Mathew, Mike de vito here, could be a weak fuel pump, have it checked. Mike De Vito

Trooper2000 is absolutely right. I am willing to bet that it is a clogged catalytic converter.