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post #1 of 2 (permalink) Old 01-17-2012, 09:48 PM Thread Starter
Join Date: Aug 2010
Location: Peterborough, Ontario
Posts: 6
engine RPM pulsing

I have a 2001 Screw Lariot, 5.4lt

Lately I've been noticing that the RPM will pulse a bit when idling.

I cleaned the idle controller and thought that it was fixed. But the next day it happened again. So - I replaced the idle controller. Again - thought it was fixed. The next day it was doing it again, but not as bad.
Then - I noticed a noise coming from under the dash.
I started playing with the heater settings and discovered that when the heater is set to floor and vent only, it stops.
When it is set to Floor/Defrost, or floor/Vent, defrost or A/C it makes a small sound. When the sound happens is when the engine pulses.

Any ideas as to what could be causing this?

Thank you

2001 F150 Screw Lariot 5.4 Lt
83 - 18' Charger DL - 2.6 Lt Yamaha Excel
16' - Tin Tinny - 25 HP JohnnyRude
wildcatt is offline  
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post #2 of 2 (permalink) Old 03-04-2012, 03:04 AM
Join Date: Feb 2012
Location: lloydminster sk
Posts: 9
sound like you have a vacum leak in one of the controll lines to a door actuator. do you have an engine light on? the only way to find the leak would be to use either a smoke machine, or an unlit propane torch, move it around the lines until the engine rpm changes and theres your leak. dont knpow if this is the best idea with the leak being in the cab, make sure all doors are open and please dont smoke, while doing so. if anyone else has other ideas by all means chime in, this is all i could think of

its not damage, its experience
tan_1 is offline  

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