just finished install of LE2 heads and cam package, along with all items to accomodate for the LE2 package... and dropped the car off to get dyno tuned... car seems to break up round 2600 rpm and shows the tach signal goes from 3100 to 300 and then goes all over... the tuner said to try and change the crank pos sensor first because this happened once before to him... could this be the opti though and does it sound more like the opti is the problem?? he saw the crazy numbers on his datalogger... just trying to get some opinions from the pros on this board
thanks

 

anyone have any ideas whatsoever???

 

Is the SES on?

 

no it is not.. the tuner said he had all the ses lights taken care of and that was the problem that he had left... the break up at 2600rpm and his datalogger receiving a crazy tach signal at that exact time

 

start with the basics, check wires, plugs, cap, rotor
usually the optical sensor is pretty strong unless you mess with it and
jack-it-up

 

All that crank position sensor is there for are misfires I am betting bad wires,cap,opti, in that order. Did you loctite the screws on the rotor inside the opti? I remember reading a while back they were coming loose.

 

the tuner replaced the plugs and made no dif so next im gonna do the crank pos sensor.. its easy and he had it happen once before... could it be the module where the coil mounts to??

thanks guys

 

Crank pos sensor doesnt do anything. I have run my car without one hooked up for 10k miles. An easy test would be just to disconnect the sensor and see if theres any difference. Usually if a sensor gives the pcm crazy readings it will ignore them.

Where I would look is the icm and the coil. The tach signal is supplied out of the coil is the reason thats what i would check. Obviously if something misfires that badly its also going to have a crazy tach output and try to stall. I would also look into valve adjustment, I have seen people get them so far out of line that the engine wont rev past 3000rpm and will break up and stutter with any type of rev.

Also make sure you have not burned any spark plug wires. Those are something that will def show up under load.

 

Tach output is from pin A13 of the PCM (94-97), meaning that is it driven based on the Opti pulse signals.