It is a little strange, but the car starts cold just fine, no missing as it idles..for a while that is. But as the engine warms up, and especially if you give it some gas, it runs rather rough.

Pulled wires, 1 at a time, and saw that when I pulled #1 spark plug wire, no change in how it ran. First, I changed spark plugs, wires, rotor, no change. Thought maybe fouled injector. Ran plenty of injector cleaner, no change.

Recently I took it to a shop to change out fuel injector on that cylinder. No change there, still ran the same. He compression tested it, it tested just fine when cranked but ignition wire pulled so it cant start.

However, when it was tested when running (engine was warm) that cylinder had no compression. He suspects a gummed up sticking valve. Told me to run some intake cleaner, try some injector cleaner again too. I ran seafoam through the engine, been doing more intake cleaner you add to the fuel too.

So far, no change. He told me its possible it may a bit to get the stuff of the valve. But it seems that usually a sticking valve happens when it is cold, and goes away after it warms up, and this is the opposite.

Any thoughts or ideas on it?

 

Just went through this... Had 2 VERY slightly bent intake valves due to an over rev. Only happened when it was warm.,.. Even then it was intermittentg, but i noticed vacuum was sub par......... lookied into the SAME things you did. and thats what i found.

 

and valve adjustment was checked?

 

That could be a definitely possibility, I remember it starting, I was driving down a mountain, and after a shift, check engine light came on, and that was when it started doing that. But it did not come anywhere close to over revving, and the timing belt probably had less than 10,000 miles on it, since I replaced the engine last year with a JDM engine and used a new timing belt.

Gas mileage still seems like it is fairly average though. The previous engine did suffer a timing belt jump and gas mileage on highway went from 32 to 26. I can still get 32 mpg though, although at 55 you can feel that cylinder missing. At 70, you cant and at other times under a load you cant either.

Wierdly enough, once I was going up a hill, and all of a sudden I could feel the engine running perfectly. I pulled over, and sure enough it idled fine. I turned downhill, it ran rough. Turned around and went uphill again, it ran fine. I never could explain that one.

And yes, valve adjustment was checked when I had that injector replaced.

 

The one thing that could cause this, you didn't mention in your write up [ distributor Cap ].
Inspect it for water spots (pourosity), carbon paths (looks like pencil lines) and other abnormalities. I'd also check (if that wasn't it):

The EGR system.
Apply vacuum to the EGR valve while idling smoothly. If it starts skipping, you've partially clogged EGR ports in the intake manifold (most likely cylinders' 2, 3 and 4).
If the engine quits, the system is working correctly.

 

But how could EGR affect engine compression though on that #1 cylinder?

 

It wouldn't. But it would dilute the incoming fuel mixture to the point that combustion wouldn't take place, thus acting like a dead cylinder; dispite correct fuel and ignition operation.

 

I just called my mechanic and ran the EGR thing past him. He didnt think it was, he thinks he is a gummed up or slightly bent valve thats not seating good as it warms up.

I do not doubt there is an EGR problem though, I have gotten a low flow code before on it. But since that cylinder has no compression after it warms up, that should not be the cause.

 

Sorry, I totally missed the "Warm - no compression" comment..
I would concure, gummed up valve.
Do you hear an unusual puffing from the exhaust when this occures (at idle)?
I would suggest a wet compression test when hot (no compression time). If the compression returns (in any fashon) that would indicate a ring condition. If you get no reaction; then yes - it's most likely a sticking valve (rare on a Honda)

P

 

im having the same problem did anyone figure out what it is

 

yes i beleive its a bent valve do you hear a slight wining from the engine? not a clicking or tinging just a wine, if so its bent valves i have the same problem in my first cylinder bin driving it for a year like that, but im thinking its about time to do a head swap or new valves just now pushing 400k on her all others still runing between 175-185 , gotta love my honda bin through hell in back, hell when i got it it had one quart of oil in it good thing i got it free well good luck and if you come up with anything else please keep me posted would really love to know