2001 Accord 5sp EX Ping Knock

2001 Accord EX Vtec
Notice the infamous marbles tapping sound when under light acceleration or pulling a hill, sometime 1-2 taps per second, sometimes more heavily.
It seems to be pretty random where it will run great for a few days, then it gets back to pinging for a few days.
Initially I thought a bad tank of fuel, I increased octane to 93 for two tanks. Exact same results, sometimes ping, sometimes not.
I have replaced the plugs with NGK platinum hoping for a real easy fix. Not the solution but they needed changed anyway.
So, I checked EGR by warming engine, then taking a 9volt battery across the pins of the egr valve and it killed the engine (per the Haynes manual). Beyond that - I don't know how else to check EGR.
I also disconnected the plug on the knock sensor and metered it with a voltmeter on very low range. I see 3 mV engine off, engine on between 100mV and 200mV as I lightly rev the engine. If I tap the motor with a hammer I can see those little spikes (like 10mV on the tap of the hammer). My understand is that this sensor is only looking for a certain frequency to give to the PCM, so this method of testing just verified that it is reading anything.
So, now what do I do? Replace the knock sensor is what I want to do - I have a feeling it might be acting up under warmer conditions as it pleases. I cannot be sure though. I'm not getting any codes indicating any trouble either. The fact that it will run perfectly some days indicates to me it is not a physical timing issue (where it would happen all the time) or mechanical problem.
The weather around here has not been above 40 degrees. Seems like the colder the day, the more I notice the ping as well, so ambient temperature is rather cold.
Timing belt/balance belt was replaced about 5 months ago by a honda shop. I just bought the car in December 2007. Problem started about 1.5 months ago.
Can runs well, noisy valvetrain in my opinion on startup, but quiets down nicely at operating temp.
Has anybody experience with this type of problem?
BTW, it is RED and has four doors. :)
Thanks!
Deacon Eisenhart
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verify tension on the timing belt.
are you sure its a noise coming from the engine? Parts corrode and start vibrating on the exhaust system around this age...
t
Deacon Eisenhart wrote:

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Yes, engine...When I apply more fuel it becomes more and more prominent.
What is the technique to verify tension on the timing belt? Pull cover and push on it?
Deacon

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and I just remembered that the Cat was replaced as well - it looks new too.
I'm still quite sure that the sound is definately coming from the engine in the form of ping...
Could it be possible for a knock sensor to go out of tolerance (where it doesn't hear the knock) yet still throw no codes?
Does it pay for me to check the base timing I can't see how it could be off the book says that it cannot be adjusted anyway...
Are there any components of the distributor that can cause trouble? Everything looks in good condition under the cap, the cap shows some electrode wear but nothing unsual.
Deacon
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Well it's been a few weeks. The microphone idea sounded better in writing.
So, I decided that is probably wasn't a knock sensor - no code being set. I clean the egr valve that didn't need cleaned and put a new gasket on - once again no EGR codes set either so I doubted that.
Went out on a limb and put SEAFOAM into the intake by pulling a vacuum line and feeding it into the engine. Crossing my fingers, I have not heard the knock since (it's been about 8 days). In theory, carbon built up on the top of the cylinder between piston top and valves could have been causing preignition conditions.
BTW, the Seafoam product really seemed to bring this car back to life - probably all in my head though. It seems to be the best "fix in a can" I've ever used so far...
Deacon
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Deacon Eisenhart wrote:

-------------------------
Sounds like you may need a valve adjustment. In addition, use lower gears for climbing hills and give it an "Italian Tune-Up" on a regular basis. (red-line it daily once the engine coolant is warmed up).
'Curly'
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Also make sure the plug or cable aren't damaged. Rodents love chewing on Honda cables for some reason...

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Deacon Eisenhart wrote:

what error codes are you getting from the computer? the motor has a crank angle velocity sensor, so even if the knock sensor has failed, the irregular ignition should be detected and set a code.
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No error codes. That is why I'm wondering why this "modern" engine doesn't notice this noise it's making and setting a code.
Again today, driving to work if I apply 15% throttle you can hear a knock. More throttle more from there, more knock. I can also now notice a difference in performance when I hear knock, once again I think confirming that it is an ignition problem. If it were a loose component, I wouldn't think I could tell.
Pulling hills I can be in second gear, not lugging the engine, and I can still hear this.
Now, on my way home from work yesterday, car is fine - acceleration is good, no knock even under full throttle.
Can valves that need adjusted cause this pinging? To me that should be a mechanical noise increasing/decreasing with engine speed.
Deacon

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I am going to stick a microphone under my hood. THen you guys can listen and tell me what you think....Might be a day or so for me to figure out how I'm gonna do it.
Deacon
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More important than exterior color and # of doors .....
How many miles are on your 2001 Accord?? Vtec is 4 cylinder?

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its been makin the noise since i bought it with 94k on it... Now its got 115k on it... I thought it was rod knock when i first heard it on the way back from the dealer! I took it back and complained...
Yes - 4cyl Vtec
only when warmed up and i am certain this is not spark "preignition" noise ---
I had read this post and you'll see my replies there that explain better...
http://www.driveaccord.net/forums/showthread.php?t 602
but it is/was the exact symptoms that the original poster had.... but i dont wanna spend the money on a t-belt change and valve adjust if the engine could go soon...
wrist pin is a theory ive heard too though.... who friggin knows...
--
stanleybb50
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