Injector pattern discussion starter
This vehicle was not misfiring when I was at the shop to test. Freeze frame was only available on P0316. Open loop so no fuel trim data that would help. Currently no misfire felt and fuel trims currently were LT+18, ST -20 and trending to lower LT. So not happening while I was testing. This had a code for injector 1 circuit. So I decided to current ramp all injector coils. Cylinder 1 is in the rear under the intake. I chose to sync off #4 for speed. I have fixed this vehicle already. So not looking for help diagnostic help. This is only to help spark discussion. So I guess discuss.
You made the diag job way too easy :) Its way cool when you can get a scope capture of something wrong, when the engine is still running ok.
Injector#1 ramp is lower than the others. Since intermittent I would say that the injector breaks down more with heat causing the misfire
Except it misfires on startup. This was a warmed up engine.
Ok. I’m between jobs and don’t have access to service info. That being said. I know we have a current flow issue. You avoided syncing #1 because under the intake So obviously your not going to check the connector yet. I’m thinking there may have been an issue with a large harness connector. Some resistance that is effected by weather possibly. I believe we see the pintle moving off it’s seat…
What happens to amperage when resistance goes up?
Where is the most likely spot to find a temp related resistance change be? Would it be a connector?
Most likely would be injector itself. Second would be the control switch. Wiring and connectors are usually heat resistant unless damaged or aged.
Lean miss when cold, with a injector current ramp like that. Just for editing purposes, your post says you current ramped the coils, when i believe you meant to say injectors
It looks like the firing order is 1-4-2-5-3-6. The current in the cylinder 1 injector circuit it low relatively speaking. The lower current in that circuit suggest that the injector has excessive resistance. That combined with the cylinder 1 injector circuit code, the cylinder misfire at start up code and the bank too lean code, I'd say that the cylinder 1 injector is the cause of your customers…
Lower amp draw on injector 1 which indicates high resistance, however there is pintle which indicates that the injector is mechanically ok and operating at this time, Longer dwell time caused by the fuel trim correction, DTC sets when cold on initial start up due to the open loop condition, ECM is not keeping that injector on long enough to get the pintle to move until it reaches closed loop. My…
While it’s true there is the pintle bump, the amplitude is much lower than normal. I suggest it moved, but very little and caused a lean cylinder.
Hmmm, did the injector really open? I see a pintle hump but if you look at the pintle hump on the good injector, it is at the peak amperage of the bad injector. I think Eric is on the right track. The pintle may have moved but very little causing a lean miss.
I agree with your thinking Bob but, do you think this slight drop in amperage would be enough to set the P0201? The customer stated when it runs bad the engine light flashes and he can feel a noticeable running problem. This engine was smooth in all ranges when I was testing. fuel trims were correcting. I do think the injector was opening and flowing at the time of this capture.
I think the pintle moved in your capture but due to the added resistance , the effective on time has been shortened because it took that much longer to build a magnetic field .Having a capture when it is cold, could show even more resistance and therefore a much shorter on time or the inability to reach enough current to move the pintle .
It would have been nice to see the voltage pattern for the bad cylinder. I believe the computer looks at the fly back voltage to judge the health of the circuit and it was probably very weak on that cylinder.