Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
Any progress to report?
No pressure, just curious. Been thinking about this one off and on. Trying to come up with something that makes sense.
I bounced around the idea of alternator ripple, but I think the effect would not be localised to one cylinder.
That got me thinking that maybe whichever ignition coil is firing at or around the time the #3 injector fires could have some huge spike and be mistriggering the injector, but I think it would have to be effecting the cam signal to do that.
Always tough to call a PCM in a case like this, but I think you've covered all the bases.
Like I said, no pressure, but please keep us updated when you make progress.
Noah PM me your address I need to send you a Christmas card for thinking about my vehicle offline. Nothing new to report. I parked it for a couple days while I went to counseling for wanting to destroy my vehicle;) but I'm back now and ready to tackle this again.
I like your idea of trying to figure out what is happening at the same time. I called the local junkyard and they have a ECU for 125. But I dont know if the old Honda HDS I have can reprogram it for immobiliser or vin identification. Have you ever swapped out a Honda ECU?
I disconnected and reconnected it. Doesn't seem to be any external signs of damage.
If I discover the problem I will post the solution for sure.
I just put a computer in a 2006 Accord that somehow ended up in several feet of standing water.
It was very easy to set it up with the Snap-On Verus. Software version 19.4 for anyone wondering. It was in the Immobilizer section, replace ECU function.
I've never used an HDS so I can't say if it will do the job, but I imagine if you plug it into the car and fiddle around for a while you'll be able to find the function if it's available.
Happy Thanksgiving
Just replaced the PCM today with a salvage part of an 2007. Good news is now we know it's not the computer. Still doing the same thing at the same rpm. It is driveable, I just tell everyone to avoid 1900 rpm and we don't see the problem. But now I know there's something else to be found. Sorry for the delay I had to get the part from ebay and the scanner to register the PCM. Then I found out I have an early model 06 that had to replace the instrument cluster (tachometer) before I could register a new PCM. See TSB under "Antitheft - Cannot Rewrite Immobilizer Control Unit"
I am making my own pcm (software and hardware). I can tell you that the most difficult job, is to take signals apart from noise (mainly ignition coils).
Maybe some spikes are triggering the driver as other guys mentioned before. But first we need to know which is causing it.
I think you should scope coil signals and spark plugs in order to match the "raising edge" of that undesirable second injection pulse.
At that point, we can add any circuit/component to kill it or the issue which is causing this.
I think you're right, I need to figure out what else is happening around the engine at the exact time that 'echo wave' pops up. Problem is every time I rig the scope I have to go out driving with it at 1900 rpm. I wish I could reproduce it in the garage. But if I rev the engine at 1900 and try to put a little load on it with the parking brake, I never see it. Isn't that weird.
Just a new idea. You can also take a look in wiring diagram and check where the noise filter is. Maybe is not working as it should
I have seen some japanesse cars which has that noise filter parallel to coil power line.
I would add some diodes in parallel with coil primary windings. Anode to control line and catode to power line (the same as some relays in market). This way you can "drain" back those peaks to the power line.
