When the car is in park and I give it a little gas the rpms go up and then when they come back down they go below down to 500 and then bounce back to 750-800.
is this normal? It's been doing it for as long as I have the car(4yrs).

 

i have the same thing. i think its normal.

 

Does it ever seem like its going to shut off? I have a problem like that but it actually cuts off sometimes.

 

no mine never shuts off. i say seafoam. im gonna do it this weekend.

 

Yeah, after awhile you begin to actually think this may be normal. But in reality, as our TL's age...........they are very sensitive to problems that can affect the vacuum and the emission controls. Cleaning the TB and intake passageways will usually help the idle. Also, some of the sensors/valves/solenoids will function at the outer limits of their operating range without throwing any codes. In doing so the fuel-air ratio can be given poor input causing a lumpy idle and poor mpg. Trouble-shooting issues can sometimes be frustrating. Tackle the simplest things first and recheck any recent work. It's easier and cheaper to try one thing at a time, rather than the shotgun approach. With a factory manual and the experience available by fellow TL owners here, almost any problem can be resolved.

 

I have been working on this issue for a while as mine actually shuts off half the time. I did the 110k service and with it you have to remove the valve covers but used new gaskets and torqued to spec and intake manifold, in my case the egr valave too since I had to remove the blower but used a new gasket. I dont know where my prob is but Im going to seafoam, clean egr ports on intake manifold and retorque the intake manifold and elbows(third time AGRRR) clean throttle body and IACV. If none of that works Im taking my chances and driving to local shop to get alternator checked and then to honda acura shop for diagnossis. Its just when you have mods some shy away but my car runs great and mods were done well, its just something little is out of whack with a leak, defective or clogged. I once had RPS move up and down but above the normal rpms and it was the air filler elbow in the fuel rail was loose and sea saw ing causeing the ups and downs. This is like I lose pressure when it is coming down from acceleration. RPMS drop slightly below norm and then either back to norm or shuts off.

 

my car does that and I think it may be cuz of EGR port and maybe sparkplugs. clean EGR and change the sparkplugs and see if it does it again.

 

When I flick the gas, the rpms hover around 1K for a second on the way down and then settle around 500.

 

u sure its 500rpm not 750rpm? 500rpm your car would idle really rough, youd feel shaking through out the whole car like it wants to die out and then comes back.
i seafoamed my car and now it doesnt do that anymore.

 

probably your EGR port is clogged up. take off your intake manafold and clean it all out and you will see a small port on the driver's side. probably 3/4 of an inch long. it will most likely be very clogged with carbon. clean that out on the intake manafold and the lower manafold and it should clear this up. I have had to clean mine out a few times - I have 143000 miles on the car now

 

If your car is stalling out due to low idle, you can increase the idle by altering the throttle cable postion