All,

My recently acquired 2004 TL 5AT Navi, bought with 29k now at 31k miles, is doing something that I have not experienced in any of my other cars before. Between 1 and 2k rpms at a stop in park or neutral the engine will shake slightly, when it is idling cold around 1100 rpms, it is rather rough, sometimes, not all the time. Around 50-55mph in 5th gear this shake translates into a slight hum or vibration. Down shift to 4th and its gone. Once the engine reaches 1900rpm in 5th it is smooth as could be. My question the community is wtf it is? Mounts are the only thing I can really see it being but they are not leaking and the engine does not move excessively during tests such as pressing the gas in drive with my foot on the brake, in fact it hardly moved at all!! The cars runs/shifts excellent and gets a consistent 25-30 mpg lol. I'm at a loss and at the same time really not too worried about it. Advice please!

 

Our engines intentionally misfire when cold. It's in your owner's manual.

There are several epic threads on the AT vibration at 50-55mph. Do a search for them.

 

Just curious, where in the owner's manual can it be found?
I would certainly find it unusual to have an engine designed to misfire on cold start as that is the time that the cat needs to heat up quickly to reduce emissions and not receive raw fuel.

OP, check into the 1500/1700 engine vibration.

 

On cold starts, the ULEV system dumps extra fuel to help warm up the CATs quicker. This causes the misfire/rough idle until warmed up.

 

Where in the owners manual? ULEV, ultra low emission vehicle sure wouldn't dump raw gas into the system and cause a misfire as that would surely defeat the purpose of low emissions. Cats warm up quickly because of the elevated idle when cold.

 

Probably under emissions, ULEV or starting procedures.

Search around, it's been discussed many times. I believe it also retards timing at the same time...Goal is to heat up the CATs quickly so they reach maximum efficiency for low emissions.


[Edit] Here's a couple of threads/posts:

https://acurazine.com/forums/showpos...1&postcount=11

https://acurazine.com/forums/showpos...1&postcount=14

https://acurazine.com/forums/showpos...7&postcount=12

https://acurazine.com/forums/showpos...7&postcount=12

 

I know it's been discussed before as I have read the threads, and the threads depicted above, purely conjecture. Discussed does mean that it is factual, that's why I want to see it in the owner's manual as stated. Anything can be stated on the Forum, but as I said before, if it dumped raw fuel into the engine it would not qualify for the low emission vehicle.

I'm certainly not trying to be a PIA, but would like reference material printed by Honda/Acura as it would be the first vehicles I've ever encountered that would misfire intentionally, and dump raw fuel into the cat when started.

 

Alright I will have to look in the owners manual but I do believe I have heard about the intentional cold misfire in my 2003 v6 accord on . I am going to have to look into this more because my engine shakes slightly when in park and revved between 1200 and 2000rpms.

 

maybe a seafoam treatment would help it out

 

I want to give this a bump to see if anyone else has a clue. Also, the rough idle does go away once the car warms up. Again, it will still shake if the engine is revved between 1 and 2k RPM when hot. Any ideas?

 

The V6's are not the most balanced and vibration free engines, that's why manufacturers go to great lengths to use counter balance assemblies and the TL vibration has been discussed over and over. Having said that, if you're in drive and the engine warm, hold the brake on and push the accelerator to get to the 1100/1200 rpm range and you'll see/feel a difference. Ours runs perfect no problems, but if you raise the idle as stated above, it won't miss or shake, but there is a noticeable vibration. Some use very soft motor mounts to absorb this and on some 4 cyl motors you can see the motor dance around in the engine compartment, but no vibration inside the cabin.

Quite a while back, I installed Mazda Competition motor mounts in our modified RX7 Turbo and there was a pronounced increase in interior awareness when the engine is running and blipped. I then installed the Comp trans mounts and removed them after 1 day. The feeling inside the vehicle was unbelievable as if one was inside a vibrator.

If it runs fine, idles fine when warm and overall driveability is fine, just enjoy the car.

 

The shaking in park or neutral means it's your motor mounts and that one is bad, thus causing the vibration. The vibration around 1500 RPM's and 50-55 MPH is due to vibrations from harmonics, there is a TSB for the 2004 TL where the dealer has to apply a dampener to solve the problem. I had it done on mine several years ago and it's as smooth as ever!

 

Sure can't hurt, but the TSB seems to be a hit or miss repair. Some have said it helped while others still had the vibration after the "fix" albeit to a lesser degree.

http://techinfo.honda.com/Rjanisis/pubs/SB/B05-017.PDF

 

I also think it may be a mount. The shop I called about would not give me advice over the phone and said they charge a 90 dollar diagnostic fee. I will try to contact the local Acura dealer for advice after the holiday.

 

Probably boils down to the mount construction so don't go crazy with repairs as I believe the rear '04 mount design was changed in '05, unless it's broken.