Injector cutting out engine misfire when injector cuts out

Maurice from Geebung Business Development Manager Posted   Latest  
Discussion
Driveability

I am looking at this for my friend Darryl Blacker who is from a Country Town in Australia. This is a Mitsubishi Triton 4 cyl Petrol (Gasoline) and has driveability issues. Have a look at the captures and what do you all make of this? We have injector current in the red which goes form about .5 amp to nearly 1 amp. The current ramp pattern and shape continues to change as you see. There are times were the current spikes and cause multiple injector fires.

I sent this capture to another Tech friend Rod this morning and he asked me where the amp clamp is placed, it is clamped straight to the wire at the ECM. Rod was eluding that if it was on a fuse we could be getting feedback. I did asked Darryl (the Tech working on this vehicle) to use another AMP clamp as I have been caught with faulty clamps of batteries going flat. So the problem is the same with different clamps.

I have asked Darryl to try disconnecting the Alternator and go from a second road test to see if we may be getting AC ripple cause these issues.

Any ideas guys?

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Walter from Sarasota

   

Technician
   

I'd be looking at fuel\fuel trim. You've got injectors firing on top of an injector firing event already in progress. It's trying to make up for a lean condition. As for the injector cutting out I'd look closer and probe it the injector may be failing due to the increased activity and or the injector driver may be failing. Measure your injector on time and do the math. It will also explain the increase in current.

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Richard from Virginia Beach

   

Diagnostician
   

I don’t have a wiring diagram or SI for this vehicle . I think you should move the amp clamp to the control wire for the injector then don’t touch anything. Test drive until it acts again and look at the scope. 

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Richard from Virginia Beach

   

Diagnostician
   

If the current ramp is normal and the spikes still appear then I think the control wire is touching ground somewhere. Make sure the clamp is at the ECM .

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Eric from Edgerton

 

Owner/Technician
 

I'm sure the lack of responses is partly due to this vehicle being unavailable in the USA and the lack of testing information provided.

Since we don't have access to a wiring diagram it is difficult for us to tell what could be causing the abnormal scope patterns. I have some questions to help me understand this system better. Please correct me where I am wrong. Where is the amp clamp positioned? It appears to be on a single wire that is providing power to all of the injectors. I believe the PCM is capable of grounding each injector individually. Looking at the fourth capture you uploaded it shows that the amp capture jumps up at times on cylinders other than #1 that you are monitoring the voltage of. Since this means you have at least two injectors opening when the PCM shouldn't be asking them to I would be looking for a short to ground in the wiring harness between the fuel injectors and the PCM. The missing injector pulse could be from the PCM shutting the injector off when it sees a miss firing cylinder, if the PCM is programmed to do that.

Now about the scope connections. The captures provided leave out a lot of information that would be helpful. When using a scope once you have verified a component or circuit it is no longer necessary to keep that connection live. Either disconnect the lead, turn off the channel or use that channel for another circuit/component. All the camshaft sensor and crankshaft sensor captures do on those captures is to confuse the issue, there is no reason to have them there. 

Those two channels should have been used to narrow down the problem. Connecting them to one of the other fuel injector circuits and monitoring the voltage would have been helpful in determining which of the injectors were suffering from the problem.

With the data provided as of right now I would be looking for an injector wire shorted to ground. One that is rubbing on something that has worn through the wire harness and is intermittently shorting the wire to ground. It seems unlikely that it would be a problem with the PCM. 

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