Belt tensioner problem now

[zwack88]

Ok all the panthers are rebelling in my family when it comes to pulleys. My dads merc has a rough idle. It has been like this since last summer but just recently address. I looked cause it felt like the car is missing. It is not it runs smooth as butter. I noticed that the tensioner is really floppy on it while running. The roughness in my cars car goes when the tensioner moves. I compaired the 2 cars running mine never moves and his is always moving. I mean it is really severe when the whole car shakes at idle cause of it. Is there something that can be tightened on it or what? He still is under warrenty but he is a busy guy during the week so droping it off at the stealership is kind of hard. If I can fix it for cheap and I can do it after dinner it works out better that way.
Thanks

[Datdambear]

The belt tensioner is not adjustable..and we do see quite a few...use a quality replacement Dayco or motorcraft...

[zwack88]

Ya I thought it wasn't adjustable cause it is spring loaded.

[p71towny]

Those wont cause it to run rough. How many miles on pops car?

[zwack88]

His car has 29.5K on it. It is just a youngin for this sort of problem.

[88MercWagon]

Time for a tune up maybe?

[HwyCruiser]

I just replaced my tensioner with a Gates replacement to get rid of a little belt slap I was hearing. $38 at Oreillys. Fairly easy job and it took care of the issue.

BTW, does 18 ft/lbs sound right for the bolt? I looked it up online and found the Mach1 spec (same engine), but that didn't seem very tight at all.

EDIT: It's 18 ft/lbs on the MM. Just FYI for anyone.

[zwack88]

Thanks. I will ask my dad if he wants me to replace it or if he just wants to warrenty it out with the dealership.