Tach not correct, truck starts missing turning right

[jmdoc66]

ok, I've been driving my truck for a year or so.(1991, 2.3, 5-speed) Runs good, but suddenly the tach starts showing about 1/2 of the correct value. So 2000 rpm shows 1000rpm on the tach. During idle, tach shows 400rpm.

The truck also started missing when I turn right. only right. I checked the wiring to make sure it's no where near the steering. I've let the truck idle and moved wires around to see if there was any open connections. Nothing.

This all started when I swapped out the negative battery cable.
Since then, I've run a negative cable/wire, from the connection at the motor to the frame, the inner fenderwell and any other negative connection I could find which were connected to the old negative cable.

Nothing.
I swapped out the fuel filter. It needed it and it was a long shot.

So any help would be greatly appreciated.

Thanks,
Mike

 

[RonD]

There should be a Ground strap on the back of the head to the Firewall, that's the main ground for the Cab Electrics so very important ground, check it.

Cab sits on rubber mounts so no connection to frame.
Inner fender and cab parts are painted before assembly so no ground there
Need that ground strap.



Does fuel level when you turn right seem to effect the stumbling?

If I am at 1/8 of a tank or lower and turn right quickly my engine will stumble because fuel pump sucks air for a second as the gasoline slosh off to one side.

 

[jmdoc66]

It happens all the time so fuel level does not affect it.
I'll check the cab negative.

Thanks,

 

[jmdoc66]

The cab to engine ground is there and tight.

Ran the codes with the key on engine off.
Received a code 88, Loss of dual plug input control

I changed the DIS module on the side of the intake and the tack started working correctly.

I swapped the inputs to the dual coils around just to see if switching made any difference. It didn't.

Truck is running like dog poop. Now its' idling really low and cutting out anytime the steering column is off center to the right. Even when changing lanes on the interstate.