IF that ground was loose I think it might cause driving problems.

The battery neg cable goes directly to the starter............except for a wire that comes off that cable and attaches below the left front strut tower. Pretty far down from the left strut towers top.

I bet the starter itself is going bad. The starter has carbon brushes. If they make good contact with the commutator in the starter, then it'll spin fast. If the carbon brushes are worn sometimes they wont make good contact and the starter will spin sloooowly.

I've had starters so bad they wouldn't spin and I had to smack them with a hammer to get to where I was coming or going from. I'm beyond that stage now.

 

The large battery negative cable ties the engine to the battery and the chassis to the battery as described in the post above. The ECU is tied to the batt neg by it's ground wires being attached to the top of the engine. The small gnd wires like the one near the wiper motor to the transmission.........are Santa's little helpers.

 

Okay I pulled the cables on the starter, they were not loose nor corroded but the pole that connects to the big wire coming down from the battery is loose (the stud going into the starter) It has about 1/16" to 1/32" worth of play when I wiggle it with my fingers. I cleaned the contacts and drove around a bit, the hesitation is still bad in the 3900-4300 range and then is somewhat constant until readline (about every 800rpm). It also stumbles a bit when the MAP sensor starts reading 0+ but after a quick warm up it started driving much better than when cold.

Could the starter cause all that? It seems like it because it drove noticeably better after this. If so I'm going to go buy a new one.

 

A new starter might stop the slow turning of the engine that you seem to experience at times. The hesitations......not likely.

Hesitations in the 3500-4000 range (when the secondarys come on line if the car is under Load).......on a series four I've had success with adding an extra ground wire to the ECU ground wires and terminating the other end of the new gnd wire(s) on the bracket that holds the ECU in place.

They are the ones in the attached jpg, looking in the wire side of the ECU plug.

They're all black except the 2C which is brown/black. You do not cut those wires. You splice into them with a new wire and solder the new wire. All but the 2C come together about six inches up the harness and you have to unwrap the harness to see where they come together. This hesitation fix works for me and other. Then again it didn't work for some others.

That said, I'd start with the 2C by itself and see if that alone does not do the job.

 

Okay, I'll give it a go. The crazy thing is I had re grounded some of the stock grounds (extra wires, cleaned the stockers etc) and I had gotten rid of the 3900 RPM hesitation entirely until my electrical system started going nuts recently.

The starter shows up on Wednesday, hopefully that'll get it going again, the company Grand AM isn't too much fun compared to the T2.