Hi all,

I completed a full valve adjustment on my 08 TL-S this weekend, and I've been having a really odd idle issue ever since. I'm hoping someone here has experienced this issue and has some insight.

The issue: When I crank the car, it will start at ~15-1600 RPM then drop to 8-900 RPM at idle, but it will ramp down very slowly (10 seconds or so). When I rev the car in park or neutral, it will drop rapidly to roughly 900 RPM then fluctuate back up and down quickly to 1000-1200 RPM until it will finally settle at 8-900 RPM (5 seconds or so, sometimes longer). When I put the car into gear and just let off the brake, after a few seconds the RPM will climb without any throttle input whatsoever to ~14-1500RPM, taking the car up to 5-10 MPH while not even touching the throttle (not a normal low idle converter roll). This is especially unnerving when coming to a stop, as the car will try to keep going for a split second without throttle input. It will also shift roughly into first when coming to a stop due to the elevated idle. If I have the car in park or neutral and pump the brakes, idle will climb to right at 1000 RPM. When I stop pumping, it will drop back down to the 8-900RPM idle.

Everything about this screams vacuum leak to me. So, what have I tried? Quadruple checked every vacuum line I removed to remove the intake/valve covers (all 5 of them). Looked for cracks in hoses or improperly seated fittings/clamps. I even removed each vacuum line independently while the car was running to see if I could zero in on the tube which might be causing problems. No luck - all of them when removed cause a much more severe high idle than what I have. I've checked my intake boot / airbox for cracking or leaks and I'm not seeing anything there. The filter is freshly cleaned/oiled. I have re-set the ECM 3 times. When I had the car apart originally, I did clean the throttle body. I did not move the butterfly until after the battery was disconnected and the TB was disconnected from the car. I did notice that the throttle body does have a decent gap when in it's idle condition, and I'm kind of wondering if my thorough cleaning is leading to too much airflow at idle now (the gap was pretty gunked up before). I know it's not the APP sensor, as I just replaced it <500 miles ago and the symptoms are the same with both the new and old sensor installed. I have no codes displayed. When I disconnect the evap canister purge control valve I get the P0443 fault, but it makes no difference for any of the symptoms. I've connected/disconnected the intake bypass valve with no difference in results. When the intake was off I replaced all valve cover gaskets as well as the lower intake manifold gasket with Acura OEM hardware. I did not replace the upper manifold gasket as it was in good shape and still had good recovery when uncompressed. I also did not replace the TB gasket, as it was in good shape, and I've read many say not to. I have the gaskets in the garage for both of these, so I could try replacing these and see what happens I guess. I know the valves are in spec - not my first rodeo doing valve work.

Has anyone had a similar experience? Any recommendations on things I should check that I have not?

 

Since you messed with the TB, you're going to have to take it to a dealer (or someone with an HDS) and have them run the ECM/PCM idle learn procedure.

 

I don't think you need HDS to do that.

Can't you just DIY like this: https://acurazine.com/forums/third-g...-happy-747662/

 

Pretty sure that in all the other TB threads, they had to go to the dealer...

 

I went through all that recently with re-setting the idle. YOU MUST USE A SCANNER. you cannot unplug the battery unfortunately, or do this or do that. you must use a scanner. I tried all those "tricks" with the car and none of them worked, only the scanner telling the ecm to re-learn the throttle position fixed it.

 

saw this online


Disconnect both battery cables. Jumper the positive and negative cables together. and let sit for 10 minutes. If you dont have a jumper wire to do this, just clamp them together with a set of vice grips. this fully discharges all capacitors in the entire vehicle. Then reconnect your battery terminals. While your doing all this make sure the cables dont touch the battery terminals. You might want to lay a fender cover over the battery to be safe. Start the car and make sure ALL YOUR LOADS ARE OFF!!! no ac, no lights, no electrical loads. Let the engine run WITHOUT touching the throttle until you hear the cooling fans cycle twice.

(Honda says 15 minutes for an idle learn, but i personally let the vehicle go through an entire warm up cycle when i have to do it on one of my customers cars. people might tell you im to cautious, but thats fine with me)

Also, a small trick with the . Before you start the car, mark on of the fan blades with a sharpie. That way you can walk away from the car and dont have to sit with it. If the marked fan blade is in a different spot, then the fans came on at least once while you were gone.

 

Thanks to everyone for the help. A quick update: I had already tried the ECM reset 3 times, but I gave it a few more shots. No dice. So, I tried battery disconnect again, this time with the jumpering of the cable in order to discharge everything. Followed the procedure above, but still the exact same issues. On Thursday I had called the dealer and set up an appointment for an idle relearn first thing tomorrow morning. It's going to cost $95, but fingers crossed that it works. I'll let you all know. Thanks again for the insight.

 

Well, the dealer did an idle relearn this morning. $103 after tax and roughly an hour wait. I got in the car and instantly knew it wasn't entirely fixed. I still have a throttle hang at start up that takes ~10 seconds to go away. I also still have the ~7-8 mph RPM rise to 1400 creep without the throttle applied. The RPM hang coming up to stops is slightly better now and shifting is much smoother. Sitting idle in gear is still in the 8-900 range and climbs to 1000 when out of gear. It's not quite as much of an obvious transition when I let off the gas to coast now, as before I could tell it was completely shutting the butterfly and basically unintentionally engine braking. It's decent enough now that I can live with it and not feel like it's a safety concern at every stop. I'm really wondering if I have a slight vacuum leak somewhere that's causing it, but it indeed does seem to be a drive by wire / controls related issue.

 

Take it back and tell them to do it right this time....

 

What do you mean by the idle hang? And perhaps they need to re-do the procedure, they may have only did your throttle position relearn but did not do a pcm/ecm reset. It's a shame they charged you that much, especially for something that litterally takes 3 mins! they probably held your car in the shop to justify what they charged you (auto shops do indeed do that, we do too unfortunately) any 3rd party garage can do it with a half decent scanner. Where I work we bought an autel maxisys scanner, and it'll do all of those goodies, no need to take to honda direct but its a bit late for you there hey!

My car after I cleaned the throttle body it had a bad idle, low idle, surging at times while driving. after the reset for throttle position and the pcm together at same time, it idles great. and surging is all gone.