Bad grounds caused my bucking!!

Nice detective work!

where where they at?

Some Help with ground problems for the benefit of other Stangnetter's...

Grounds are important to any electrical system, and especially to computers.

1.) The main power ground is from engine block to battery: it is the power ground for the starter & alternator.

2.) The secondary power ground is between the back of the intake manifold and the driver's side firewall. It is often missing or loose. It supplies ground for the A/C compressor clutch and other electrical accessories such as the gauges. Any car that has a 3G alternator needs a 4 gauge ground wire running from the block to the chassis ground where the battery pigtail ground connects.

3.) The computer has its own dedicated power ground that comes off the ground pigtail on the battery ground wire. Due to it's proximity to the battery, it may become corroded by acid fumes from the battery.

4.) All the sensors have a common separate ground. This includes the TPS, ACT, EGE, BAP, & VSS

5.) The O2 sensor heaters have their own ground (HEGO ground) coming from the computer. This is different and separate from the O2 sensor ground.

6.) The TFI module has 2 grounds: one for the foil shield around the wires and another for the module itself.

7.) The computer takes the shield ground for the TFI module and runs it from pin 20 to the chassis near the computer.

8.) The computer's main power ground (the one that comes from the battery ground wire) uses pins 40 & 60 for all the things it controls internally.

If you have access to a digital voltmeter and would like help diagnosing grounds, make another post and I will try to help.

I recently tore my engine down to do heads and a new timing chain. When I pulled the main engine ground bolt out of the timing cover I discovered something very interesting. Only the three or four first threads where any good. The remainder of the bolt threads and the cavity in the aluminum timing cover had been eroded by arcing! I will be reattaching this ground to the head when it goes back together.