Idle at 750 RPMs warm intermittent chug down every 5 seconds or so turn AC on and chug gets worse and more frequent and throws it into p1381 3000 RPM rev limit check engine light on.... i Clear code and raise idle at throttle cable wheel to 1000 rpms... everything runs perfect no p1381 no chug no check engine light but when I turn AC on idle lowers chug starts p1381 rev limit same thing..... 1500 RPM everything runs perfect even with the AC on but idle is too high for safe shifting auto trans ..... Alt checks out good .... thank you thank you very much

 

P1381 is Cylinder Position Sensor (CYP) intermittent interruption. Usually a problem w/ sensor, but diagnostics are necessary to confirm sensor fault and not a wiring or PCM fault. Intermittent problem makes fault detection difficult, problem only detectable when present.

A shop manual and VOM are necessary to isolate fault. Shop manual can be purchased online from automanualsource.com for $22. This has fault tree to be followed.

good luck