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. :)