this is the problem: 97 1 ton dually 2wd. auto.
tach either does 1 of the 3 following:

1--bounces all over the place.
2--drops n stays at 0
3--works fine.

when the tach acts up so does the volts gauge. also the od kicks in n out. or if the tach is at 0 we loose od. also when we loose the tach we have to manually shift the tranny. otherwise if u stop its like its taking off in drive.
also when we loose the tach or it acts up the warning lights do 1 of the following.

1--just the gen light comes on
2--GEN--CHECK ENGINE--W.I.F.--T.T.--W.T.S.
3--no lights come on.

have done the following:
1--2 brand new batteries
2--swapped computers
3--swapped alt.
4--new ESS.
-------put on n adjusted to credit card width. worked fine for 350 miles.
then it acted up. adjusted to the card folded in half n worked fine for 300 miles. acted up again. stopped n unplugged the TPS. plugged it back in n moved the wires so they weren't hitting the throttle cables. ran perfect for 1000 miles.

i also noticed that the throttle cabale is held on from falling through the gas pedal by a pair of vise grips. n also on my scan tool the TPS on my truck that runs perfect idles at 23. n the truck that is acting up it shows 6.

i unplugged the TPS on the truck thats acting up when it was acting up n wouldn't shift gears n it had no tach but none of the warning lights were on. n it had no effect the truck still drove.


anyone???

should the 2 TPS at idle both show 23 n what does that # mean on my scan tool. n shouldn't off unplugging the tps n running like that have done something?

trying to drive home n also fix this while on the road.

 

ok i just noticed this also. if i have the fan on. it runs fine. if i shut it off the tach will act right up.

also i noticed this about the TC locking n unlocking. it does it if i let off the gas just a little bit n get back in the throttle.

no vacuum lines are hooked up on this truck, as the guy before me took it all out. so i have no cruize. no heater controls except the fan on/off n low/ high n also heat or cold. n thats it.

any ideas??

 

well now even with the fan on if it will act up as soon as i let off the throttle. it seems if i keep it about 70 mph it will be fine.

now even at idle it will do it the tach will act up.

we are just sitting here ideling and the tach will drop to zero and my power invertor that is hooked up to power my laptop will start beeping as if there is a surge of power or something.

what is going on here??

 

try replacing the crank position sensor.

 

it is new.

 

now it acts up all the time. if i floor it then it clears up. we finally had to pull over in mississippi an stop for the night.

 

That means it's even more likely to be bad.

 

the output speed sensor on the trans both wires were cut in the same spot. could this cause this?? i put butt connectors there n now the truck is acting worse.

also i noticed the rubber ring on the dampner is coming out like 1/8th of an inch. could this cause it too??

 

i finally unhooked the crank sensor n drove 50 miles that way. got sick of that n pulled over folded a credit card in two gapped the sensor to that n plugged it back in. haven't even had a flicker or anything in the 700 miles since i redid it.