A Slight Miss
#12
The EGR injects smallish amounts of exhaust gas into the intake, to cool the combustion temperatures (already burned exhaust gas cannot burn again) and reduce nitrogen oxide emissions.
It only does this while cruising, and at lesser throttle openings (the situations under which you are experiencing the misfires). The cooler combustion temps allow a bit more aggressive spark advance.
It is of course not possible to make a 100% certain diagnosis without having seen, heard, and smelled the car--however my experience has been that the subtle misfire you describe is caused by one of two things.
As I typed that I went back to look at your signature, and see you have a CAI--did you remove the MAF screen? More about that here...
It only does this while cruising, and at lesser throttle openings (the situations under which you are experiencing the misfires). The cooler combustion temps allow a bit more aggressive spark advance.
It is of course not possible to make a 100% certain diagnosis without having seen, heard, and smelled the car--however my experience has been that the subtle misfire you describe is caused by one of two things.
- The EGR valve being sluggish;
- Removing the MAF screen;
As I typed that I went back to look at your signature, and see you have a CAI--did you remove the MAF screen? More about that here...
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Matt's 95 Stang
5.0L (1979-1995) Mustang
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10-05-2015 07:16 AM