Sudden drop in RPM's
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Sudden drop in RPM's
1985 F150 5.0 EFI -
Engine starts fine. Idles fine. However, every so often there's a sudden drop in RPM's and the engine struggles. This happens when in park and also while driving. The drop in RPM's is erratic and happens not continuously, but sporadically. It seems as though the computer is making adjustments albeit too slowly, and when it hits the sweet spot, the RPM's go back to normal.
I've looked for a short in the engine harness and can't detect any. I also tried to pull the codes with my Actron CP 9690. It is OBD II and OBD I compatible and also has a STAR mode. However, the codes were cleared and until I get some miles in the truck, it won't register any codes.
TPS is working. IAC is working. MAP is working. EGR appears to be working. Thermactor unit appears to be working. I'm scratchin' my head boys! Suggestions?
Your time and efforts to help are appreciated.
Engine starts fine. Idles fine. However, every so often there's a sudden drop in RPM's and the engine struggles. This happens when in park and also while driving. The drop in RPM's is erratic and happens not continuously, but sporadically. It seems as though the computer is making adjustments albeit too slowly, and when it hits the sweet spot, the RPM's go back to normal.
I've looked for a short in the engine harness and can't detect any. I also tried to pull the codes with my Actron CP 9690. It is OBD II and OBD I compatible and also has a STAR mode. However, the codes were cleared and until I get some miles in the truck, it won't register any codes.
TPS is working. IAC is working. MAP is working. EGR appears to be working. Thermactor unit appears to be working. I'm scratchin' my head boys! Suggestions?
Your time and efforts to help are appreciated.
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From: Sheffield, AL
Have you done the "shake" test? Be very careful [watch for moving and hot parts!!!] and while the engine is idling and the hood is open, grab different sections of the wiring harness and gently shake. Listen for a change in idle speed.
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Yes - I did a shake test. There was one time I heard a sudden shift in the suction of air through the throttle housing and it ran better, but I've not been able to repeat it doing a shake test. But the problem does seem electric.
I will continue to try to see if I can create the same, sudden change by carefully examining/shaking the wires.
Thanks!!!.
And to Gary...thanks for the reply! I think all vacuum lines are good (all replaced a year ago).
I will continue to try to see if I can create the same, sudden change by carefully examining/shaking the wires.
Thanks!!!.
And to Gary...thanks for the reply! I think all vacuum lines are good (all replaced a year ago).
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I tried to pull the codes with my Actron CP 9690. It is OBD II and OBD I compatible and also has a STAR mode. However, the codes were cleared and until I get some miles in the truck, it won't register any codes.
Lead Driver
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From: Sheffield, AL
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Thanks, ctubutis!
Using my Actron, I get nothing at all. I've run through all of the possible tests, KOEO, KOER, and STAR. It runs through the cycle and there's no data whatsoever.
I used the Actron on my other vehicles with great success. So it works fine. Must be something with the Ford.
I also tried to run codes using my check engine light. Nothing there either. Ideas?
Steve
Using my Actron, I get nothing at all. I've run through all of the possible tests, KOEO, KOER, and STAR. It runs through the cycle and there's no data whatsoever.
I used the Actron on my other vehicles with great success. So it works fine. Must be something with the Ford.
I also tried to run codes using my check engine light. Nothing there either. Ideas?
Steve
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