Cant seem to figure this one out. 2007 Impala 3.5, 380000km but well maintained. Runs great for about ten minutes or until you give it a lot of throttle. Then the tach stops working completely. Getting engine misfire code and crank sensor code. Checked all wiring leading to crank sensor and found broken wires and repaired them. Tried new crank sensor, nothing. New plugs and wires also.
Thanks
Tyler

 

Are you still getting the same error codes?

Could be coil pack, or you have addition broken wires or loose connection somewhere.

You probably need to verify the signal. The tachometer is getting the same signal the coil and ignition are getting. If your tach goes off line and the car still runs then it is likely a short from the ignition to the tach. If it stops running or runs bad then its from the ECU to the ignition. Anytime you find broken wire that goes to the ECU it is a little scary. You do run the risk of damaging the ECU.

It is all pretty simple. The ECU gets a signal from the CPS sorts it out and tells the ignition to fire. Sometimes there is a separate wire from the ECU to the Tach sometimes the tach just picks up off the ignition. If there is a separate wire for the tach and the ignition it could be a more global problem such as the ECU itself.

The other thing that is a clue is you said it runs fine for ten minutes or so then goes haywire? That suggests a heat related issue. Perhaps something is getting hot, expanding and loosing contact.

Also I would use quality factory parts from somewhere like http://www.newgmparts.com/. I have seen more than one bad AM part out of the box from the local parts store.

 

thanks lot for your input, im going to take another look tomorrow and let you know what I find.

 

NP hope you find the issue. A wire diagram would be very helpful on this.

 

clean the mount where the crank sensor bolts on , mine run buildd up put the sensor out of tolerance