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Honda's with rough idle

Numerous postings refer to Honda V6 engines that have a loping idle at around 80k. They eventually display a Code 1399? Which is actaully caused by multiple cylinder misfires. Don’t waste time amd money replacing parts needlessly.

This problem is not a tune up, vacume or egr issue, it’s caused because the V-Tech engines don’t have hydraulic lifters. There are two intake valves, one is barley opened at idle, the other is opened at higher rpm, thus when the adjustment is off a little it affects the delicate combustion balance just enough that the car nearly stalls at idle, the computer detects this drop in rpms and compensates for the drop in rpms with a little more fuel. This condition disappers at higher rpm because the other valve opens.

It’s a very delicate balance at low rpm so even a lttle discrepency in valve adjustment can break the bank.

Also those intake manifolds are notorious for clogging in the egr passage way. You have to take the upper plenum off to remove the valve covers anyway. Use a drill to expand the egr passage located on the driver’s side and you think you just struck a coal vien in West Virginy.

Adjsut those valves, all twenty four of them,the old fashioned way with a “go and no go” feeler gause and ream out that egr passage and it will run like new.

The down side is that if you can’t do it yourself it’s big bucks, Alldate says 4.6 hours just for the valve adjustment, not to mentions valve cover gaskets and the extra labor for reaming out the manifold.

Trust me, if you don’t do these two things all the plugs,wires, rotors, egr valves etc. won’t solve this problem

What years??

Mine is a 99, I think that was the last year of that v6 with a distributor and wires.

FYI It now runs better than ever. There is a TSB regarding code 1399 a proprietary Honda code that refers to either a clogged egr passage and or both. I switched back to NGK plugs from autolites and it runs even better.

Good Luck

I have a 07’ and was concerned if all V6 Accords suffered that problem.

Your post only accents two points that I carp about all of the time on this board.
One is that a compression test should always be performed when working with an engine performance problem.
Two is having regular inspection/adjustment of the valve lash.

Excuses such as “low miles, shouldn’t have a problem” and “the factory says the lash does not have to be checked until oblivion” does not apply in the real world.

The majority of car owners can get away with ignoring this procedure. The minority that do not get away with it usually face premature premature engine problems; burned valves/seats or damaged adjusters/cam lobes depending on whether it’s too loose or too tight.
The gamble is determining whether you’re in the majority or minority.