Honda J35 Valve adjustment, affect idle quality

I would test vacuum as Trav suggested. Maybe then a good scanner if possible, and if you did the motor mounts yourself you can handle the valve adjustment too. But I kinda find it unusual for the valves to need adjusting at 120k, but you never know!
 
It's not unusual. Some intakes will likely be a few thou loose, and some exhausts will likely be a few thou on the tight side. Totally common, and I even check the K24s I own every 50K because I have seen them hang an exhaust valve open enough to cause misfires well under 100K
 
If the valve clearance is too tight, it can adversely affect idle quality. Check the MAP voltage at hot idle, should be under .9.
Absolutelly- doing this can save alot of unnecessary work and $900 in your case. It did for me. Buy a cheap scanner to check (5 min.) and can use for other tasks.
 
I would test vacuum as Trav suggested. Maybe then a good scanner if possible, and if you did the motor mounts yourself you can handle the valve adjustment too. But I kinda find it unusual for the valves to need adjusting at 120k, but you never know!
Checking the MAP sensor readings with a scan tool is basically doing a vacuum check with the ecm's own vacuum gauge, it can be be verified or on engines with no MAP with a scan tool/scope and transducer which is basically all the MAP is a vacuum transducer. If someone has the equipment thats fine but for the average DIY at home a primitive old vacuum gauge will get the job done.
 
If you plan on keeping the vehicle, do the valve adjustment. It is due.

I did my `06 Odyssey with the J35A7 engine at 168,000 miles and afterward was way quieter and smoother. I should have done it sooner. The exhaust valves were 1/2 the clearance they should have been and the intakes were double what they should have been.

While it is apart do the throttle body cleaning. Plenty of YouTube videos available for support.
 
I was passenger in a sedan with a J-Series V6 before and after a valve adjustment at 97K. It made a noticeable difference in idle quality. I often see used cars with J-Series V6 engines for sale with mysterious misfires and rough idles that I suspect is due never having had a valve adjustment. One of these days I want to buy one of these cars and try my luck at seeing if a valve adjustment and belt tensioner is all they need.

I also had a problem with an overly rough idle in a car with a J series V6 a couple of years ago, so much so that it was an obvious problem. Cleaning the throttle body fixed that issue entirely and now it idles very smoothly. At 227K the car now revs and idles like butter.

Be careful if you decide to clean your throttle body, it is very easy, but should you take care to appropriately handle the butterfly valve as it is drive by wire and word is that you can damage them if you are too rough.
 
Really ? The timing belt was done at 100K miles and they didn't do the valves? That is crazy. Never use that shop again.
 
? Its a common sense thing, for someone in the know.
Debatable. They are usually sold together, along with plugs. But not every engine truly needs it. I know a lot of folks who only get the timing belt pkg and plugs done at 100K, and never develop any issues from not adjusting the valves.
 
I am sure this has been discussed a million times about Hondas in general but, a quick search really didn’t provide anything recently relevant. I have a 2015 Accord V6 with 120,000 miles and really do not know if spending almost $900 at the dealer was the right thing to do for a valve adjustment. The Indy mechanic was not that much cheaper to be honest because I called them too. Normally I would not worry about this because engine runs great, except at idle in gear I can feel the engine vibration through the steering wheel and into the cabin. Common with 4 cyl engines but was not expecting this with the V6. With that said I have changed the motor mounts with oem, cleaned the throttle body, ran Techron through the tank, new plugs, and timing belt was done at 100,000.
I am kind of out of ideas and didn’t know if valve adjustment would affect idle quality at all and if this is something that I could do myself. I am do have mechanical ability and have been inside engines before not never has to adjust valves. What do you all think?
My guess is a faulty injector. I had a similar issue, car ran fine no loss of power but idled rough at traffic lights in D (auto tranny).

Drove it like this for a while, then it felt like it could possibly stall so took it in.

Long story short injector on cylinder #2 was shot. New injector, runs like new👍
 
Really ? The timing belt was done at 100K miles and they didn't do the valves? That is crazy. Never use that shop again.
I had an Indy shop do the timing belt. So funny story is that I asked my local dealer right down the street from my work about a valve adjustment a couple months ago. They flat out told me that they almost never do them and that id be wasting my money. 😂
 
In my limited experience, when rough running is caused by valves, it’s too late. Especially at idle, when not much pressure, airflow, or heat is involved. In my experience, valve problems show up if the seat is damaged, or the valves have run too hot and are causing pre-ignition, which shows up more under load. So, valve adjustment problems would not be the first thing I’d suspect. Now, if it’s due before issues develop, then do it. You might sample the gaps on the front side bank to get an idea….

honda egr clogs in the v6 … that will cause idle and cruise roughness in the v6, via clogged passages. the repair is a manual intake-off and scrape/drill out passages.
 
What I'm about to say has more relevance on engines that don't have variable valve timing because the effect is only true if an engine has valve overlap at idle speeds.

When you make changes to valve clearances you are also making small but real changes to valve timing. Perhaps it's only a couple of degrees and in the scheme of overall valve timing, of little consequence, but as a percentage of valve overlap at idle it's a more significant change. If clearances are tightened valve overlap increases with the effect of some fuel mixture going straight out of the exhaust which results in an overall weakening of the idle mixture. Before the days of idle speed control I've seen engine idle speed rise simply by opening up the valve clearance by two thou. The engine ran more efficiently and more smoothly because overlap reduced.

Don't know if this applies to a Honda V6 but it's one reason why clearances need to be correct.
 
Checking the MAP sensor readings with a scan tool is basically doing a vacuum check with the ecm's own vacuum gauge, it can be be verified or on engines with no MAP with a scan tool/scope and transducer which is basically all the MAP is a vacuum transducer. If someone has the equipment thats fine but for the average DIY at home a primitive old vacuum gauge will get the job done.
The scanner comment was more for live data like the injectors if the OP did not see a problem on a vacuum gauge. I should have been more specific. I also "assumed" that the OP did the timing belt himself if he did all the motor mounts. I don't trust anyone to align the crank, to all other shafts, but maybe that's because I've never paid anyone to do a timing belt or anything else on any of my vehicles.
 
Back
Top