Puzzling Honda CRV
Not sure where to go from here. This CRV while cruising will hiccup (so to speak). Scan data shows a very short lean condition (only one data frame). Feels like an instantaneous four cylinder misfire. Put the scope on the crank sensor, tdc sensor, ignition trigger for one COP, and one injector signal. I chose the COP at random. The ignition trigger signal to whatever coil seems to skip 360 degrees and then gets back in sync.
Scan data shows that it many cases it stutters just after VTEC turns on. There is another intermittent problem that sets an AFS heater circuit code. Could it be related? When the cut out or stutter happens closed loop running looks normal.
Need some testing advice. CKP and TDC sensor grounds do not go back to PCM they go to the same grounding point as PCM grounds on intake manifold. Have tested powers and grounds at PCM.
The 1st questions that come to mind are is the oil full and is it clean? I have had a few of these do really weird things with a few quts low on oil or really dirty oil.
Oil is full and looks relatively good. Vehicle has 200 000 miles on it.
agreed with other guys. ck oil level. also any codes fix them first! clear codes recheck. Does this happen under load?
Yes under load and no codes at the time.
Hey Ronald, Sounds like a classic need of a valve adjustment. Not hard to do, just little time consuming. have cured many of these types of problems. Definitely check it.
Plus one on checking the oil. I haven't seen a heater issue cause a drivability issue but stranger things have happened. I believe these vehicles were prone to valve adjustment issues causing intermittent misfire/rough running.
with 200 thou on it and the valves have probably never been adjusted..... That would be a good place to start as well.
The scope trace shows that the ignition trigger is skipping an event. I don't see how valve adjustment would have anything to do with it.
Possible ignition coils breaking down under load ? Do they appear original ?
The coils are new but if you look at scope trace you can see channel D (yellow trace) the trigger that turns the coil on and off goes out of time and skips an event while the cam and crank signals do not change.
No answer here just further observations from waveforms and a recap of sequence of events: Injector pulse drops out prior to mistimed ignition trigger signal Ignition trigger signal occurs 360 deg in advance after injector pulse drop out - firing on exhaust stroke Injector pulse returns but also mistimed by 360 deg advanced (in time with ignition trigger signal) Ignition trigger signal and…
This is a great run down of the situation. Can’t wait to see what the actual issue is.
It appears that the PCM is losing track of #!, re-assigning it at 1 rev off, then recovering #1 position and assigning it correctly. I would be looking at how the PCM ID’s cylinder position.
Your description of the event matches my observation. It seems to very shortly loose synchronization. I was not sure if once synchronization (cylinder id) was established on start up if the computer algorithm keeps looking for sync or just counts ckp teeth. Anyways I now have a theory. I found a known good ckp, tdc, cmp relationship waveform and it is obvious that this CRVs ckp sensor to tdc…
You're right, the TDC narrow toggle should align with the 2 narrow ckp toggles.
Ron, After a little digging their appears to be some issues with the chain tensioner failing over time in these K series motors. The exhaust side is on the slack side of chain and relies on the tensioner to do its job. There is good article here to read about this :superstreetonline.com/how-to/engine… I also attached a troubling shooting flow chart for the DTC P0341 CMP Sensor A…
This may be far fetched but what if it thinks it is in a decel? Its happening so quickly I am doubtful that is what is going on but might be worth watching TPS on a test drive. Fuel Supply System Fuel Cut-off Control During deceleration with the throttle valve closed, to the injectors are turned off to improve fuel economy at engine speeds over 930 rpm. Fuel cut-off action also occurs when…
I don't think it is far fetched as I had the same thought. An intermittent TPS drop out will cause an open loop fuel cutoff event. It is at least worth checking before diving into some of the more deep stuff.
A shorted O2 sensor heater can cause a lean condition if it is shorted to the signal wire. Not sure if it is relevant to your situation though.
cam /crank correlation doesn't seem right. But also I can spot ckp glitch perhaps due to coils firing and sometimes pico count 13 falling edges per 360 degree rotation and sometimes 14 falling edges. Maybe you need more samples per capture to catch it (maybe not once 10 microsec, but 1 microsec)
Sometimes the Pico will count 13 or 14 falling edges, because of "noise" but if you count the toggles, you always count 13 toggles.
It is possible for electrical noise to seep in through the oscilloscope leads, though sometimes it is hard to tell for sure.
The scope is counting the ckp pulses between the 360 degree cursors, but it may count a "noise" as a ckp pulse. If the scope leads are routed too close or touching 10kv to 30kv ignition coils or spark plug wires, the scope will pick up the extra ignition noises. If spark jumps to a scope lead, it could damage the scope.
Update info. Customer had timing chain replaced 5000 miles ago. Noted some power loss at the time but did not have the cutting out problem. Not sure if we are going to get the go ahead to retime the engine.
in my technical point of view, the Cam and Crank waveform are good when the igntion trig…r at wrong time. So could it be a PCM fault?
Got the go ahead to retime engine. Exhaust camshaft was one tooth out. Runs good now. Problem solved. What was going on? I think at one exhaust cam tooth out the tdc pattern was ending up right on top of the ckp pattern and slight mechanical variations would move one signal from one side to the other side of a rising or falling event. This would mess up the tooth count and mess up the…
Thank you very much for the update and conclusion!
Car is fixed and running well. The exhaust camshaft was out one tooth. I am attaching a picofile of the proper relationship of tdc signal and ckp. My thought is when the exhaust camshaft was out one tooth the tdc (exhaust camshaft) sensor signal was switching voltage at the same time or very close to the same time as the ckp signal and at certain conditions the synchronization of these signals…