Hey fellas,

My '99 TL-P has been having a real rough idle at stops lately. Been getting worse every day. Watching the OBD scanner shows the RPM bouncing +/- 100 RPM from where it should be while idling at stop. It doesn't really follow a pattern, it kind of stutters about randomly. Accompanied by furious steering wheel shakes - but I bet that part is just due to the bad engine mounts that I STILL haven't replaced.
From my research online and from speaking with people who know more of cars than I do, this seems to suggest a dirty IACV, maybe in general a clogged-up intake system. I got some carb cleaner and plan on giving all those parts a deep clean today after I return from the office, but I wanted to see what ya'll think of the issue.
I recorded a video of the shakes yesterday afternoon. Make sure to turn the sound up so you can hear it.

https://www.youtube.com/watch?v=Skph...ature=youtu.be

 

Sound all the way, UP, still very difficult to hear, your issue. Bad engine mounts, coupled with a dirty induction system, would certainly contribute, to the symptoms, you describe. Had a similar issue, with my 03 TLS, when i bought it, 4 years ago, at 196lK, no check engine light. Removed the intake, and thoroughly cleaned the Air Induction System. After the clean, the ( Mildly), Rough Idle, as well as, the ( Mild ), RPM Fluctuation, were both eliminated. The induction system on my car, was not clogged, like many, Iv'e seen posted, on this Forum, but it was far from CLEAN! The dirtiest part of the system, was the IACV, which I believe, to have been the cause, of my idle issues. It cleaned-up really well, and I saw no need to replace it. So far, 4 years, and 43K later, my car still idles, the way it should. Removing the top Plenum Cover, and examining the upper half of the Intake, should give you a pretty good idea, of the overall condition, of your Air Intake System. Happy Motoring, and Keep the Shinny Side UP!

 

Sorry about the bad video, haha.
I took out the butterfly valve and the all the stuff connected to it, and gave it all a deep clean yesterday with some carb cleaner and a wire brush for the dirtier stuff. The IACV was incredibly clogged! There was this mud-like substance almost entirely clogging one of the chambers, and the rest of the system was covered in what looked like carbon buildup. After giving it all a good scrub-down and re-installing it all, I ran the idle re-learn procedure. Ran a graph on my scantool after to plot out the RPM, and it's much much steadier!
Wow, what a difference! The idle is smoother than it's ever been since I got the car, and she sounds oh so nice when I turn the engine over in the morning. I have to be a bit harder on the brakes now, as it seems like all the car wants to do is go, haha. By the way - is 1k RPM normal when you're in Park? I might have to adjust the idle later, as it seems a bit higher than it should be,.... sitting in D4 with my foot on the brake doesn't have the same affect.

I'm hoping my valve goes the same way as yours, frankjnjr, with no replacement needed.

I think this weekend I'll pick up some replacement gaskets from the dealer and take care of the rest of the intake manifold. I only got to take a glance into it last night, but I'm betting it's equally as gunked up.

 

I'm glad it worked. Regarding the 1K rpm engine idle, 1K is about 250 rpm high. I'm not certain, how to adjust the idle, but you may want to wait, until you address the rest of the induction system, and see, if that service, impacts the high idle. Normally, there is no need to buy the large metal gasket, that fits directly beneath the plenum cover. You should be able to clean it up, with some brake clean, or carb / throttle body cleaner, and re-use it. It's my opinion, that whenever possible, using a TOP TIER fuel, aids in keeping the fuel impacted areas of the engine clean. Honda, nor Acura, to my knowledge, do NOT, recommend, the use of ANY, fuel, or oil additives, in their engines

 

Yeah, I think the idle issue comes from me having to disconnect the throttle cable to take the IACV out far enough to work on it. I had the positions of the throttle and cruise control cables switched, so I didn't pay too much attention to how I installed it afterwards - I bet I messed up the position of the throttle.
I'll look at adjusting that throttle cable down a bit after I've cleaned out the rest of the manifold tomorrow morning.
Alright, if the plenum gasket looks fine I'll just clean it up. The gasket that goes between the intake manifold and the butterfly valve looks a bit aged on mine, so that's the one I was thinking of replacing.

As for the fuel, when I first got the car, I ran it with low-grade fuel for a few months,... I ended up using some sort of cleaner to help remedy the situation, but I'm sure that I'll be seeing the affects of those months tomorrow morning when I'm knuckle-deep inside the manifold haha

 

Curious abut Your progress. If, there was some way to install a new IACV, without removing the entire throttle body, again, I'd do it tomorrow! Out of curiosity, I recently visited a PickNPull yard, which had 11 2G TLs, in stock. I picked the dirtiest, rattiest, ugliest one of the bunch, and pulled the IACV. It was clean as new, and not showing any evidence, of ever having been replaced! Go figgure!

 

Left all the gaskets as they were, as I didn't feel like driving out to my favorite Honda shop that day. They seemed fine anyhow haha
Manifold and IACV were super grimy, almost looked like mud inside one of the cavities of the IACV! It was crazy.
Three bottles of carb cleaner did the trick though - idles super smooth and purrs like a giant cat now.
This past weekend I noticed that my MPG had taken a hard hit, so I figured I'd go ahead and fix the throttle cable since the buddy I was visiting had multiple sets of open-ended wrenches. Fiddled with it by eye and got it idling cleanly at a nice 800RPM with no load - according to the specs people have shared here, that should be close enough. MPG is now higher than it's ever been since I got the car : )

 

Still trying to identify, which TYPE of mysterious, Honda inspired, tamper-proof, (screw head), is used to secure the one sensor, to the IACV! I have, pretty much, every hex, torex, and odd type bit, known to MAN, but, I don't have THAT one! Honda, for sure, didn't intend, for that sensor, to be removed! Did you find it difficult, to remove the IACV, itself. When I removed, the one at the local picknpull recently, I found it impossible, to turn one of the two securing screws. I ended up, snagging the sides of the screw, with a pair of visegrips. After, two or three, very, very difficult, hard turns, the screw head, finally, broke off!

 

Oh, are you talking about that weird 5-sided star? I didn't look at it too closely at first and went for the Torx bit, but that definitely did not fit.
I actually ended up leaving those screws alone, as they only keep that sensor on the metal body thing. There are some other bolts on the main body of the IACV that connect it to the rest of the throttle body. Those came off easy-peasy for me.

frankjnjr, do you know if there's a brand of O2 sensor that's recommended for our 2nd-gen TLs? I know people say not to use the Bosch spark plugs, so I'm hesitant to pick up the Bosch O2 sensors.

 

As far as 02 sensors go, I favor OEM. Costs more, but it's performance characteristics, are exact! IMO