5.7 tbi tps electrical issue

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21jtb12

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HELP!!! I have replaced my dizzy and timing seems a little off. It will idle ok but kinda harder to start then before. I put a whole new dizzy in, other things have replaced are:
1)rebuilt throttle body
2)fuel injectors
3)iac
4)tps
5) coolant temp sensor
6)map sensor
7) fule filter
8)wires,plugs
The list goes on and on honestly. Any way what I'm wondering is when I test my new TPS sensor with the key OFF, im getting 1.50-1.60 v at my signal wire(middle blue wire) and when blip throttle it goes up to about 5v or so and back down. But when I turn key on it goes OL and doesn't show any v at all. Turn key off and walla kinda works. Truck runs but has no power and boggs down like crazy with any bit of throttle. Pulling my trailer and mower I probably would have been better pulling my truck with the mower.lol. idk what else to do. Oh let me mention also that iv had the truck for about a year now and the odometer has never worked and idk how long it was not working before I got the truck. But odometer stopped at 191,694.9 miles. The truck is a 88 gmc c1500 2wd auto transmission. 5.7 sbc 350 Tbi. Oh and when driving exaust kinda sounds like it hollow or something or maybe like a eco. But if try to give it any kinda hard throttle it'll pop and almost die. Please any help would be greatly appreciated. I am self taught diyer with a little sense. And wanting to learn more. Thanks in advance for any help
 

PlayingWithTBI

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when I test my new TPS sensor with the key OFF, im getting 1.50-1.60 v at my signal wire(middle blue wire) and when blip throttle it goes up to about 5v or so and back down. But when I turn key on it goes OL and doesn't show any v at all.
That sounds weird. You shouldn't see any voltage at the gray wire or blue one, with key off. You may have an issue with your ignition switch which sends power to the ECM and sensors through the ECM/IGN fuse.

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Here's a link to a bunch of FSMs.

 

21jtb12

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Yeah thats what I had read and it is completely opposite, and I was considering the ignition switch also but its not very old maybe a year or so. And what about the fuse block could it be shorted or one of my relays maybe? And another crazy thing is from what I can tell thats the only thing that has power with key off under the hood and iv never had a dead battery since I put a new one in year ago. How would I go about testing the ignition switch possibility. Oh and im on a very limited budget so any ideas of things can do or make myself would be great. I am pretty good at making things or modifying. And thanks for your response
 

PlayingWithTBI

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A scanner will tell you what's coming on and what's not. Look at your MAP sensor, it gets the same 5V reference as the TPS. Then go from there.
 

21jtb12

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I have a bluedriver scanner but thats all and I think its only obd2. Thanks for the help im about to start checking things now. And do you know what pin on the aldl should have power?
A scanner will tell you what's coming on and what's not. Look at your MAP sensor, it gets the same 5V reference as the TPS. Then go from there.
Thanks man for the diagram. This this has been giving me trouble since iv had it and finally think I got it. PO had wired in a connector for the ac and had the power going to ground on top of thermostats housing. Same power wire as map and tps. Cut the wire boom were sounds GOOD!! Now to adjust the timing
 
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