Surging and possible miss
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Cargo Master
Joined: Aug 2012
Posts: 2,856
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From: Kaufman TX
Surging and possible miss
I'm not familiar with these engines so wanted to solicit some feedback.
After replacing injector cups and shimming the injectors back to spec my engine has improved from taking a very long time to start, to starting up basically immediately.
What has not changed however is that it will surge after it starts, indefinitely, until you give it some throttle for a second or two and then gently bring the RPM back down. Then it will bog slightly down to ~ 400 rpm before coming back up and settling in ~ 600 rpm but with a noticeable shake. It feels like a miss, and I can still kind of feel it even with more rpm up to about 2k but after that it's hard to feel. Nothing changes as the engine warms up. The engine does not blow smoke at all out the exhaust.
I've managed to do a buzz test using "Cargauges Pro" and all the injectors sound loud and identical.
The next step that I can think of is a compression test.
But, before I back under the valve covers are there any other things I should be checking?
Video - Idle not surging:
Video - Idle and surging:
After replacing injector cups and shimming the injectors back to spec my engine has improved from taking a very long time to start, to starting up basically immediately.
What has not changed however is that it will surge after it starts, indefinitely, until you give it some throttle for a second or two and then gently bring the RPM back down. Then it will bog slightly down to ~ 400 rpm before coming back up and settling in ~ 600 rpm but with a noticeable shake. It feels like a miss, and I can still kind of feel it even with more rpm up to about 2k but after that it's hard to feel. Nothing changes as the engine warms up. The engine does not blow smoke at all out the exhaust.
I've managed to do a buzz test using "Cargauges Pro" and all the injectors sound loud and identical.
The next step that I can think of is a compression test.
But, before I back under the valve covers are there any other things I should be checking?
Video - Idle not surging:
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Cargo Master
Joined: Aug 2012
Posts: 2,856
Likes: 936
From: Kaufman TX
I think you're absolutely right. I'm about 95% sure this was originally an automatic and was manual swapped. I've been doing some digging on this and this thread with 2 references to surging on startup caused by a faulty MPLS, and the surge will clear up if you give it some throttle. Exactly the behavior I'm seeing. I went and pulled codes and I have P0708 - Transmission Range Senor Circuit high Input and P0713 - Transmission Fluid Temp Sensor Circuit High Input.
I don't believe a manual ECU would be looking for either of those.
Anybody happen to know the concept of operation for the MPLS? If it's voltage based I could make a voltage divider to provide an effective result of "transmission in neutral". I think my other choices are get a manual ECU, or get a chip but I'd prefer to have stronger evidence they'd solve the issue before I drop hundreds of dollars on a guess.
I don't believe a manual ECU would be looking for either of those.
Anybody happen to know the concept of operation for the MPLS? If it's voltage based I could make a voltage divider to provide an effective result of "transmission in neutral". I think my other choices are get a manual ECU, or get a chip but I'd prefer to have stronger evidence they'd solve the issue before I drop hundreds of dollars on a guess.
Hotshot
Joined: Dec 2012
Posts: 11,271
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From: Las Cruces New Mexico
Ah just saw your last video, strong chance the ECU is for an Auto. Also
my truck also surged when I installed split shot injectors on my truck with single shot tunes, and since you don't know the history of it I would remove the VC and inspect the injectors and see if they don't have AD or AB on them.
my truck also surged when I installed split shot injectors on my truck with single shot tunes, and since you don't know the history of it I would remove the VC and inspect the injectors and see if they don't have AD or AB on them.
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Cargo Master
Joined: Aug 2012
Posts: 2,856
Likes: 936
From: Kaufman TX
Ah just saw your last video, strong chance the ECU is for an Auto. Also
my truck also surged when I installed split shot injectors on my truck with single shot tunes, and since you don't know the history of it I would remove the VC and inspect the injectors and see if they don't have AD or AB on them.
my truck also surged when I installed split shot injectors on my truck with single shot tunes, and since you don't know the history of it I would remove the VC and inspect the injectors and see if they don't have AD or AB on them.
I did get a good look at the injectors and they are AA
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From: Mexico
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Cargo Master
Joined: Aug 2012
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From: Kaufman TX
Yes. That's what happens when an automatic computer doesn't "see" the auto through the sensors. A user on this site was kind enough to reprogram my ECU to a manual strategy and the surge on start up is gone.
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Joined: Jan 2007
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From: Mexico
I have been searching for a fix to my surging problem for 2 years.
My mechanic found a broken wire in the trans sensor wire harness. One we reconnected the wire the surging went away. I replaced the sensor (probably original) and harness.
Thanks everyone for your help.
My mechanic found a broken wire in the trans sensor wire harness. One we reconnected the wire the surging went away. I replaced the sensor (probably original) and harness.
Thanks everyone for your help.
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Cargo Master
Joined: Aug 2012
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From: Kaufman TX
Wow. Bet it feels good to finally slay that dragon.
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