my mother in law came to visit and her grand prix started taking a dump, when she starts the car it runs ok for a few seconds and then starts making nasty noises, i looked while the engine was running and could see the tensioner bucking around. i loosened the belt and checked all the pulleys and they all seemed to move. i am not a pontiac person, dont know much about these cars my sister had a ford contour and it did something similair and it turned out to be the tensioner. i plan on taking the belt off and letting the car run for a few minutes to see if it comes back, if it is the tensioner, how do i get it off????
tia.....

what motor is in the car? 3100 sfi? 3800? I know that the tensioner on the 3100 comes off by a single bolt, 15mm i believe. More than likely the 3800 is the same way.

it is a 3800, i took the belt off and the motor wont run at all, with the belt on, it starts and then runs rough for a few seconds and dies. i dont see anything that has come loose, i was able to spin all the pulleys except for the crank of course. my mother in law drove this car 400 miles to my house without having any problems until she tried to start it in my driveway. anybody have ideas on what i should check for???

You said you cant spin the crank? Can you turn it back and forth about an inch? I remember on these older 3.8's the harmonic balancer would break down and become loose. Causing sort of a chattering metallic sound. Not sure if the new ones are much better. Its very odd that your car wont start and run for a few minutes with the belt off.

i didnt try very hard to spin the crank because i didnt think it would move much at all by hand? but yeah i thought it was wierd it wouldnt start with the belt off, with the belt on it would start and then about 3-5 seconds later start running rough and die, i looked around on this forum and saw a guy with similiar issues, unplugged the MAF and that didnt make a difference, took out the IAC thing and pushed it in and that didnt make a difference either. if i have my foot on the gas she'll stay running but she doesnt sound good. she's gonna have it towed to a shop tomorrow so i'll post back on the verdict. thanks for your help!

ok it was in a shop that i trust almost all day, as it stands right now they are saying the plugs and wires are beyond bad (150K and they say the plugs are original) and they cant go any further until those are changed. i dont really get that because any car i have ever had (i take better care of my vehicles than she does obviously) when plugs or wires start getting flaky you start having loss of fuel economy and other driveablity issues before you get to the point where the motor just wont run anymore......
:screwy:

bad ecu they say.