Hello everyone.

My beloved 99 Monte Carlo LS with 3.1 and about 180K miles is exhibiting some strange behavior and I need advise.

I recently moved from East Coast to California and had been experiencing a strange phenomenon with the car wanting to idle high whenever in park or neutral. I believe I've fixed that by replacing the plastic tube that runs from the top of the air intake to the front tapper cover as well as goes to the back side. I'd also replaced the Engine Idle Control Valve just in case.

It no longer idles at 1500 rpm anymore but is behaving like it's having an issue with the transmission.

I had a mechanic convince me that this Seafoam Trans Tune-Up would change my life and poured this concoction into my transmission. I'll say that at first it was much snappier in it's response, however now is a different story.

Since I've been driving the car more and more here in So Cal it's been vibrating every time I stop the car and have it in gear. It will do it in Park or Neutral as well but just not as bad. You can both hear and feel it. Car never once tries to stall or sputter and rpm's stay steady.

Has anyone else experienced this and what steps did you take to resolve the issue?

Your help would be most appreciated. I use this car for my job which is requiring me to travel a lot and a transmission replace or repair would kill me financially. I'm hoping it's not the Trans.

 

first, there is no such thing as a "MECHANIC IN A CAN"...first lets try this first...check the trans fluid level and fluid condition and see how contaminated your fluid is...if it is doing this in park or neutral, it may not be trans related...check to see if you have any bad motor mounts, especially the dog bones...put the car in drive and power brake it...have someone see if there are any broken motor mounts while you are power braking it...make sure that you have your PARKING BRAKE on while doing this, so you don't run over your help if your foot should slip off the brake lol...also recheck for any other vacuum leaks...

 

forgot to say as well...it sounds like you may have a misfire in a cylinder...you may want to check all your plugs and wires as well as your coils...remove all the wires to the coils and check for corrosion...if you do have corrosion, take some sand paper or emery cloth and sand the corrosion off..