There is huge interference when I rev the engine on bluetooth through my pioneer car stereo, I've re-grounded the stereo and changed the base unit,face and mic for the stereo.it is still the same.

The AppRadio Mode is a feature that is built into some Pioneer car stereos, which allows users to control and access compatible smartphone apps directly from the car stereo display.
If your iPhone 7 is paired to your car stereo, but you are unable to play music over Bluetooth, it may be because the AppRadio Mode is currently active. To resolve this issue, you'll need to disable the AppRadio Mode on your Pioneer car stereo. This can typically be done by pressing a dedicated button on the car stereo, or by accessing the settings menu and selecting the option to turn off AppRadio Mode.
If you need further assistance, I recommend consulting the user manual for your Pioneer car stereo, or contacting Pioneer support for more information.

check the bluetooth version on both units. which is newer? the phone or the radio? they may just be incompatible.

Verify that your phone's mic is working when attached to a bluetooth device (other than the stereo). This is to verify that it is the stereo and not your phone. If it passes you may want to try deleting the numbers in the stereo's bluetooth memory and then pair your phone to the stereo. I believe your stereo only holds three numbers.

Check the ground on the battery and the engine for proper conection. Cheap brand stereo also causes engine noise

you can try disconnection the power to the radio for 5 minutes (all the power not just the main power) then reconnect it and see it it reset.

on the radio fh-x700bt I can recive a call but I cant talk back they cant hear me talk

Yes, some of their radios do have problems with the rca outs, the same thing has happened to me.

if they are all positive speaker wires then each speaker will get a positive and the other speaker wire goes to the ground of the ground wire

You can get replacement wiring harnesses from Pioneer (www.pioneerelectronics.com) or from a local stereo shop that sells Pioneer product. Also, check Ebay...there are often times harnesses for sale for any model of radio from all across the country.

the phone itself is having a problem connecting fully with the pioneering car stereo you may need to use a motorola one