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  #1  
Old 06-26-2019
Debugjaws Debugjaws is offline
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Default 8V92 Intermittent surge at idle

91 WB, 8V92, 60K miles. I have an intermittent engine rev / surge at idle. Typical idle sits at 600 RPM. Twice now I've had this surging occur, where it will either modulate back and forth between 600 and 700 RPM's, or it will raise to 700 RPM's and stay there. Each time this has occurred, I shut off the engine and re-started, and the issue stopped.


Sounds to me like a throttle position issue (if these have such a sensor), fuel flow, or other.


Any thoughts would be greatly appreciated.
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Gerry Lefebvre
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  #2  
Old 1 Week Ago
Debugjaws Debugjaws is offline
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Still having this issue. Idle surges higher towards 800 - 900 RPM's. Pretty consistent if I've run the cruise. Could there be an issue in the high idle circuit? Something tied to the cruise circuit? Maybe air throttle? Getting ready for a 800 mile round trip. Doesn't effect while driving, only at idle. Any thoughts are appreciated.


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Originally Posted by Debugjaws View Post
91 WB, 8V92, 60K miles. I have an intermittent engine rev / surge at idle. Typical idle sits at 600 RPM. Twice now I've had this surging occur, where it will either modulate back and forth between 600 and 700 RPM's, or it will raise to 700 RPM's and stay there. Each time this has occurred, I shut off the engine and re-started, and the issue stopped.


Sounds to me like a throttle position issue (if these have such a sensor), fuel flow, or other.


Any thoughts would be greatly appreciated.
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91 WB 40'
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  #3  
Old 1 Week Ago
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brhodes brhodes is offline
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Have you checked your engine for any error codes?


It sounds like an issue with a dirty ground, or a dirty pin connection in the engine interface plugs in the front lower main electrical panel. Open the front panel and check the Amphenol connections on the road side.
Another possible thing to check is a dirty throttle psosition sensor on the foot pedal or loose connection.

Also, clean the ECM plugs of the engines computer as fine dirt can get into these.


One more thing to check is the MAPP sensor on the side of the blower behind the ECM.
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Old 1 Week Ago
captainbb captainbb is offline
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Gerry did you ever get silver leaf? I ask because it will tell you what percentage the throttle is at, thought it might help with troubleshooting.
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Old 1 Week Ago
Big Fro Big Fro is offline
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Do you experience surging while going down the highway without cruise? But, with cruise there's no surging? If so, it's your TPS.
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Old 1 Week Ago
Debugjaws Debugjaws is offline
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Quote:
Originally Posted by Big Fro View Post
Do you experience surging while going down the highway without cruise? But, with cruise there's no surging? If so, it's your TPS.
No, it's only at idle. However, I experience it at idle if I've been using cruise. The other day I experienced it right at ignition.
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Old 1 Week Ago
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Randy Dupree Randy Dupree is offline
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The old mechanical Detroits would sometimes get a "roll" at idle.
It was common and the buffer screw would take the roll out.
I'm not sure at all if a D deck engine has a buffer screw.
Barry?
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Old 1 Week Ago
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No, all DDEC engines are electronic controlled so there is something his computer is seeing to tell the injectors to add additional fuel at idle which is why he needs to see if there are any codes registered, clean all the plugs as suggested or even may need to upgrade his EPROM Stabilizer kit in the computer to the last version #154 if it hasn't been done.


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Old 6 Days Ago
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and make sure MAP and TPS sensors are correct

no loss of voltage when this is going on or having bad spots with DOMV during testing
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  #10  
Old 5 Days Ago
Debugjaws Debugjaws is offline
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Quote:
Originally Posted by captainbb View Post
Gerry did you ever get silver leaf? I ask because it will tell you what percentage the throttle is at, thought it might help with troubleshooting.
Hi Brian,

Yes I did. Thanks for the tip. I'll check it out on this next trip!
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