So I've been scouring the internet...found a thread which lead me to check my ignition timing against my vs AFR - whenever my AFR spikes (very high levels ~ 26+) my timing is pulled which makes sense, so now this is leading me back to it being a fueling issue - does that make sense to you?VStar650CL wrote: ↑Mon Jul 05, 2021 8:49 amNot sure why it would be affecting the ignition timing, but the fact that it doesn't misbehave cold means it's probably related to closed-loop (warm) versus open-loop (cold) operation. During open loop, the ECM pretty much ignores the A/F's and O2's and riches the mixture to prevent cold stalling.
V Star, my upstream O2's were just changed and the car is staying in closed loop based on my scanner.VStar650CL wrote: ↑Mon Jul 05, 2021 2:49 pmThat looks like a smoking gun to me. Your A/F shouldn't be topping out like that. Hard to say without a voltage scale, but it looks like it's over-responding when the ECM tries to do normal closed-loop oscillation. You might simply have a shot sensor on one of the banks.
The ECM is supposed to rich-and-lean the mixture cyclically for the cat, that's normal. But they're usually little bumps and they don't make the timing go nuts. You sure the new sensors are the right ones?ken in az wrote: ↑Sat Jul 10, 2021 12:51 pmOnly thing I can think of is that the ECU is trying to light off the primary cats by retarding the ignition timing. Sounds like it's doing it on purpose for emissions purposes. How to make it stop doing that - I dunno?? I know my car's cold start sounds a lot more aggressive for the first 15seconds or so, then it goes ack t normal. Not sure if that's the same thing but I have heard that it sounds like that to light off the cats for emissions.
Maybe contact a reputable tuner for the G37/370Z crowd since they use VVEL like us.
Yea, this is what is driving me nuts, it seems very much like an ECM issue or at the very least a sensor/circuitry issue. I thought it was the ECM braking feature, but the dealer says it is normal. It definitely feels like its the engine braking feature, but in overdrive.VStar650CL wrote: ↑Sat Jul 10, 2021 1:45 pmWell, the reason the ECM does that is to make the rear O2's react so it can monitor cat function. The rear O2's have no other job -- we have a saying that the fronts are for the engine and the rears are for the government. But like I said, it should go a little rich and a little lean. I've never seen timing fly all over the place while watching it dynamically, so something has to be making the ECM overreact to what should be normal injection cycling.
Yea I noticed they are way down in the valley. This is a real good suggestion tho, I'll try to dig into it today if I can get the time.VStar650CL wrote: ↑Sat Jul 10, 2021 2:05 pmHmm, you know, this just could be a defective knock sensor, or maybe there's enough carbon in your engine to be knocking whenever the ECM tries to lean the mixture. Now that I think about it, it occurs to me that knock response in most ECM's is instantaneous. Timing gets dialed back at the first hint. I know the knocks are impossible to reach on a VK without major disassembly, but if they're on the usual sub-harnesses, maybe you can unpin them at the sub-harness connectors. It'll throw open circuit codes for the knocks, but if the timing quits jumping with them disconnected, you found the culprit.
I had a feeling you'd say this, lol. And I 100% agree, but I don't think the knock sensors are faulty based on the (now confirmed) wide RPM range that this is happening at and the fact that it only happens when I let my foot off the gas or at low/partial throttle. I took the car on a WOT drive to make sure that my RPMs weren't limited to 3500 and under, I was able to get above 4k on a test run.VStar650CL wrote: ↑Sun Jul 11, 2021 8:53 pmHate to say it, but resistance on the knocks doesn't mean anything at all. They're ceramic sensors which are mechanically tuned to the audio frequency of knock, and they can easily test healthy on an ohmmeter but have mechanical or frequency response that's off in the weeds. To prove they aren't falsing, they need to be disconnected.
Ken, car has been going into open loop when I take my foot off the gas at any random speed. Every time it goes into open loop, my AFR sky rockets (extreme lean) and my ECU pulls timing to about -7°. The car bogs down unless I blip the throttle. Acceleration and overall performance has been low since this all started months ago.
Just an update - I installed the new pump and the my ignition timing has all but disappeared. The deviation that you saw in that graph above was not normal, and it is no longer happening. I believe that the pump was leaking fuel into the crankcase so there is still some issues with my intake and exhaust timing, but I think a few oil changes will fix that. Now I'm just praying my piston rings and cylinders are unscathed, we shall see.VStar650CL wrote: ↑Sun Sep 12, 2021 5:16 pmI think you're just seeing the ECM dialing-back the injector pulse width when the throttle is dumped. What will actually show up in the rail is an integral of the pressure produced at the pump and the pressure released into the cylinders, so those bumps at the bottom are most likely the injectors being dialed back while the pump's command pressure hasn't been altered. You could put up a graph with injector pulse to confirm it, but I'm pretty sure it isn't abnormal.
That makes perfect sense, the possibility of a bad seal or diaphragm didn't occur to me. Good job and good info!