I checked that IC out, won't work. Its lowest frequency it'll operate at is 100Hz, I need 60 Hz. Thanks anyway!

I finally did some testing with the actual solenoid and my ckt. Problem is at either end of the scale the solenoid stops pulsing. With my Fluke 87 in duty cycle mode it stops under 15% and above 63%. Almost like the FET isn't being properly turned on. I know that it needs at least 4+ volts to turn on so yeah it drops below that at 15% and below, but up top at 65% its still has 6 volts AC but the solenoid just turns on.
I also had a chance to monitor what the ECU in my car is doing when PWM the line pressure. At idle it's center frequency is 60Hz, the duty cycle was 7% (yielding 70psi of line press.) and the AC voltage was a constant 11 volts.
My ckt never even reaches 11V. As mentioned earlier the input voltage (AC) to the Gate equals what the Drain is doing. It starts out at about 3.5V rises to about 7V then back down to 3V. So I need to maybe boost the voltage inbetween the 555 and the FET? Simple 2n2222 ckt. or op-amp voltage follower with a gain of 2???

 

First page of this topic, 2nd post. MRMEVAL suggested it.

 

Are you using a solenoid identical to the one in your car (the one you measured)?

 

Are you using a solenoid identical to the one in your car (the one you measured)?

Yes, I have a set of solenoids out of the car.