Engine miss when using AC
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Joined: Nov 2004
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Engine miss when using AC
1995 E150 Van 5.8L. w/6K miles on a complete MotorCraft parts tuneup including wires, plugs, distributor cap/rotor. It has an intermittant miss at idle but not under way. It's a noticable miss when sitting at a stop light at idle with AC on. Doesn't seem to do it w/o AC going. Thoughts?
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Joined: Mar 2005
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In my experience when you run the AC the vacuum that the engine puts out is about 2-3 less. So if you normal vac is 16 then with AC on it might be more like 14. So any vacuum leak would be more noticeable. I have been chasing the same hunting idle and intermittent miss on my 91 E350 for about 6 months.
Changed out Idle air control valve,Air charge sensor, EGR valve and position sensor, temp sensor and O2 sensor. And changed out some vacuum lines. Everything seems to help some but still have that intermittent miss. I tee a vacuum guage into the fuel pressure regulator and see "good vac" of about 16 at idle. But then unplug some other line to create a leak on purpose and the vac reads about 14 and it still runs ok most of the time. So as others have suggested check all your vacuum lines and see if any sensors are coding.
One code I get is a 12 which is something about cannot raise engine rpm.
Good luck and be patient.
Rob
Changed out Idle air control valve,Air charge sensor, EGR valve and position sensor, temp sensor and O2 sensor. And changed out some vacuum lines. Everything seems to help some but still have that intermittent miss. I tee a vacuum guage into the fuel pressure regulator and see "good vac" of about 16 at idle. But then unplug some other line to create a leak on purpose and the vac reads about 14 and it still runs ok most of the time. So as others have suggested check all your vacuum lines and see if any sensors are coding.
One code I get is a 12 which is something about cannot raise engine rpm.
Good luck and be patient.
Rob
