Pilot 2003 EX - In-Cylinder Testing Waveform

I used a pressure transducer with a 0-150 psi range; .5v = 0 psi & 4.5 = 150psi. Here is my waveform on cylinder #4, I see that the peak is a bit low but I cannot find what is contributing, I did observe a bit of oil on the spark plugs, engine has misfire in at least 4 cylinders, Bank 1, 4, 5 & 6. The misfire on the #1 appeared after I swapped the plugs from cylinder 4 & the misfire stayed in 4 as well. From this waveform, can someone spot something I'm not seeing, I see vacuum (0.254v = ~ -9psi); valve opening is right at .5v which is 0psi for this sensor. The high peak is 2.033v = ~ 57.5 psi; I will do a reading with a needle gage but for those oscilloscope savvies, I thought I would ask here to see if there are any anomalies that I can't see. Red trace is computer control on/off for the ignition (unplugged).

Disconnecting the Coil does not change engine RPM which means the misfire is constant, this car can run without 3 plugs lol; good O2 sensor compensation to keep it alive.

Looks OK to me at first glance :huh: Compression towers aren't leaning, the decompression and intake vacuum levels are equal enough. No excessive backpressure, as far as I can tell without looking at the capture file myself.

Peak running compression may be low? The old rule of thumb is that running is 1/2 to 1/3 of static. Have you done a static compression test with a gauge? It may be valuable to compare your running with static.

There is a misfire in this cylinder and owner has changed plugs and coils since it had marked down about 3 misfires at the time on this bank. Unfortunately these banks are monitored by the same O2s so I can't confirm which side is bad. I have a feeling this is a valve issue that is a bit loose thus causing the misfires. I noticed that when I accelerate I can get the short fuel trim to be around 1 and long term about .80. upstream O2 oscillates all the time, car does not lose power during acceleration. Misfires are marked on 5 cylinders when accelerating. Downstream O2 goes lean when accelerating (around 0.1). I was hoping I could have a sample of what a valve lash gap issue looks like under a scope.

If it helps, I've always had much better luck identifying valve lash issues on these engines with a pressure pulse sensor, instead of in-cylinder.

I took this off an '05 Odyssey which would set miss codes on all cylinders, but only count misses on #4. A pulse sensor on the intake showed a corresponding low intake pull on #4:

I noticed that when I accelerate I can get the short fuel trim to be around 1 and long term about .80.

I'm surprised it's not throwing a P0172. :huh: Rich trims are another indication of a valve lash issue, IMO. With the engine fully warmed up, no loads, in Park, what is the MAP sensor voltage? We'd like to see .9V.

I have collected enough data in regards to that with the Verus Pro (multiple PIDs) I will share that info when I get home. I also noticed that he EGR valve is sitting at 1.86-1.88 when not operating, Verus pro says it should be around 1.2v when closed. This to me seems like the EGR valve is partially open (dirty), I cleaned the EGR flowpath that feeds each cylinder as they were all clogged; unfortunately I have not cleaned the EGR valve because it is almost melted down on both bolts lol so I will probably needs to replace the base along with if it if I break it. I replaced the $4.00 PVC valve as it appears to be open all the time. Car has no issues starting now as it used to but the misfire is present; of course it also flags the VTM-4 light with the miss. I don't think the MAP is that low in voltage, this is another thing I was suspecting since the vacuum goes lower as I accelerate and peaks when I decel for a split ms but I will have to confirm that when I look at it.

AguilarPro wrote: I have collected enough data in regards to that with the Verus Pro (multiple PIDs) I will share that info when I get home. I also noticed that he EGR valve is sitting at 1.86-1.88 when not operating, Verus pro says it should be around 1.2v when closed.

Ah yeah, that'll do it! :silly: The Verus is right on. Shame on me for not thinking of that earlier. :blush:

You could always try giving the valve a few love taps with a small hammer/flashlight/screwdriver to see if the valve will free up.

Tapping the EGR did not move the pintle unfortunately lol (I have watched too many ScannerDanner videos using the hammer tap) . I was watching the scanner data while I was doing this. Sometimes it would get stuck around 2.0X when I manually activated it and I got it to shutdown after a second try but the PCM does not flag it so I guess it doesn't affect it much. During acceleration it does have some activity but goes back to closed really quick.

So, I checked the MAP value and noticed that it is about 1.4 at idle and when I rev it up, it has more compression. The only time I noticed it went higher was when I snapped the throttle as you can see in the capture, I also included O2 captures & Fuel trims. Am I looking at a intake leak or under reporting map?

So, I checked the MAP value and noticed that it is about 1.4 at idle and when I rev it up, it has more compression. The only time I noticed it went higher was when I snapped the throttle as you can see in the capture, I also included O2 captures & Fuel trims. Am I looking at a intake leak or under reporting map?

I still think you're looking at a stuck open EGR. The trims get better off idle because there's more air entering the engine, so the mixture dilution effect isn't as severe.

I think you have enough evidence to justify getting that EGR valve off somehow. :lol: Once you get it off, you can confirm the valve hanging open, AND plug the intake port and recheck the MAP and your trims.

You can do a quick rationality check on the MAP by observing the voltage KOEO. Should be right around 2.8V. The BARO PID should match your local barometric pressure.

Did I mention I get random misfires on at least 5 cylinders during accel and maybe around 3 when idle? They all appear to be consistent, I tried to get vacuum waveform with my eBay transducer but it did not work lol. What I did is, I went back to check the in-cylinder waveform and I feel like the valve is not fully closing. See my picture when zoomed in vertically.

So I removed the EGR and it was a bit open, pushed it back and reinstalled it, I think it got permanently stuck when I reseated it and now it won't actuate lol, I tried manually doing it and didn't work. Computer threw a code on if after driving it like 10 miles or so, the code was due to EGR not lifting xD.

I did not see any misfire codes stored anymore; maybe needs more driving. I notice that when it is at idle and I monitor the misfires, I get "Yes" for 2 cylinders but I think is not something that is bad just the car having misfires every now and then. I test drove the car and I got no misfire events during my drive or light. I think it needs more driving, I did have a temporary code set for the EGR but no misfires, I believe this slightly open EGR was causing the misfire.

I got the PV500 and tried monitoring the pressure changes in the intake and I do not see activity; maybe I got a bad one. I guess I will have to get one of those absolute transducers to use for these type of things. I will eventually get the WPS500. I will post back to confirm if this was a fix. PCV valve was stuck open too so there was always airflow from there as well, together with the partial open EGR may have been a fix.

Test Drive data; MAP is better 15 vs 10 (now) with EGR closed.