I have been chasing this fault for months now. When starting the engine it will sometimes rev to 3000rpm then slowly drop back to idle (1-3 secs)
Something forces the ICV to open way too far, then it settles down and ICV returns to normal opening. For now I have a restrictor I made fitted in line with the ICV so it just cant rev over 2k even if it opens further.
I have no air leaks and have tried changing for good known used units the following. ICV, AFM, ECU, CTS (correct one for the TC loom) 6 pin TPS has been linked to maintain the signal for idle, I have changed the CPS twice as I now have code 19 stored but no fault lamp lit.
All earths have been checked, cleaned and rechecked.
Here is the code its giving me.
19 - RPM signal (crankshaft sensor) Incorrect signal
AC volts read 3.9 to 4v at idle and 8v @2k rising with revs. I dont see any voltage on cranking but that may be my digital meter.
Can someone please check the signal off their CAS so I can compare?
I really am running out of Idea's now as to whats causing this.
This may be a red herring but the starter motor when cranking the engine will sometimes stall like its trying to crank an engine thats miles too advanced, let go of the key and crank again and its fine and the engine starts. Its not always true that the stalling starter proceeds the hi rev startup btw.
Battery is brand new and starter terminals good, main earth is direct from battery to starter.