Hey guys,

I have an '08 TL with only 61,000 miles on it. It's been flawless and a great car. Just had the timing belt replaced by the dealer due to age a few weeks ago and all has been well. Until today, all of a sudden it does not like idling when warm, or starting (warm or cold, you have to give it some throttle). It will idle high when cold fine, but as soon as it starts to idle down with the temp rising, it idles very rough. Sometimes it will almost stall, then rev up to about 1,000 RPMs for a few second, then when it tries to idle again it goes back to running rough. Listening to the engine run with the hood open, it sounds like a slight hissing sound near the passenger side of the intake manifold, near the serpentine belt. There's a few vacuum hoses in the area, but wiggling them doesn't seem to change anything. But I've never paid much attention to this engine and this could also possibly be a normal sound? (unrelated belt/pulley noise?)

Any thoughts?

Thanks,

Mike

 

Start by spraying some carb cleaner around the area of the hissing sound. If you hear the idle alter, you've got a vacuum leak. If that doesn't do anything, spray around other vacuum sources to see if it alters as well.

 

No misfire / random misfire codes?

 

Thanks guys, I'll try the carb cleaner today. Also, there are no codes.


thanks,

Mike

 

Sounds like a definite vacuum leak somewhere..

 

The good news is if you can hear the leak, it shouldn't be all that difficult to isolate the point of the leak. Simply create yourself a "Redneck Stethoscope" (a length of garden hose or even a vacuum cleaner hose) and wave it around the engine bay until you've found the source of the hiss.

To find really difficult vacuum leaks, plug up all exhaust outlets except one, plug the throttle body, and then plug a compressed air line into the remaining exhaust outlet, turn on the air and then spray soapy water all over the engine bay; when you see the bubbles you've found the leak.

 

I think it's more than likely valve spec
It could be a vacuum leak, shit gas, intake / throttle body issue
But those symptoms sound like it's leading to misfires caused by valve spec

 

Thanks for the help guys. Haven't had a chance to look into it much today, but the car finally threw a code today for the EGR valve.

Majofo - what's valve spec?

Thanks,

Mike