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Discussion Starter · #1 ·
My truck has been a turd lately.. now its stumbling and or missing on accelleration. Heres the part that kinda confuses me / reassures me its only electrical, it dosent do it when its cold. But once warm it will just run like total crap anytime i try to accellerate. Dosent matter if hard accelleration, soft, or just trying to make it up a hill. We have a Snap-on Verdict scanner at work which does OBD1. Hooked it up, had no codes, and being obd1 it can only read and diagnose so much, but MAP, TPS, CTS all tested ok. So i guess its leaned down to 02 sensor (1 month old), ecm, or something else. i just wanted to get some opinions before i throw money i dont have at it. Im kinda leaning towards O2 but i am sick of replaceing them darn things.

also, when coasting (not engine brakeing) in gear, once it reaches about 1600 rpm the truck and revs jerk back and forth. any ideas?
and one last thing, my gas guage will randomly get pegged at E for about 30 seconds, then slowly rise back up to normal. bad connection or sending unit?
Thanks everyone, i need to get this thing all figured out before winter :p
 

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Let's tackle the gas tank issue first: That's a simple sending unit problem. You will need to drop the tank, pull the fuel pump, and then replace the sender. I purchased mine on ebay for $40. You can get them direct from an isuzu parts retailer but they're $90.

Have you replaced your intake manifold gasket yet? Checked for vacuum leaks?
 

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Maybe your injectors are dirty poor spray. Smooth when cold ??? Have you pressure washed the engine?? How long has it been since a tune up ?? Temp sender to CPU going bad.
Might just be basic crap in tour gas tank... Messed up the sender and now affecting runability. Definitely start there and two birds with one stone.
 

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Discussion Starter · #5 ·
Ok, i guess the sending unit will wait.. because id like to replace the pump while i have the tank out, the pump sure has to be tired, after 166k of being ran on e most of the time.
As far as the IMG, I kinda ruled that out, seeing as it would cause a high idle, wouldent it? my truck is iding about 700RPM, and every few seconds it will stumble and idle at about 5 for a sec of two. Also, all the vaccume lines are less then a year old, and none seemed disconnected.

I did pull all the wires, each one sparked so good i could almost hear the spark over the engine.

Tommorow i will get some videos of it idling / accellerating.
I need to figure this out, driveability has gone down the s**tter, and im reallllly not trying to just dump money into it, Im trying to pinpoint the exact problem.
 

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Have you changed your fuel filter they will make it have poor power. It didn't sound bad but if you where holding it to the floor that's not good. Maybe your cats are plugged. Two things to check!!
 

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Discussion Starter · #8 ·
Fuel filter has about 1.5K on it, there is good pressure going to the fuel rail. i opened the schrader valve with a screwdriver and gas shot everywhere.
The cat is gone :oops:
 

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I wonder if the tps is not functioning properly. You didn't get an animal up in your air filter by chance did you plugging off the air???
 

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Discussion Starter · #11 ·
I was able to view the TPS output on the scanner at work, seemed to function perfect.
And im absolutely stumped here. Im supposed to be a "mechanic" and i have no idea :(
 

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So lets check this out from the beginning, you said running like a turd before it started missing. How long had it been like that?

Running good cold but failing to perform once at running temp... That should rule out a few things, like fuel supply system. Lets look at what changes between a cold & warm engine. Temp sensor (ecu) reading changes, temp sensor (gauge) reading changes, cold fast idle valve closes (forgetting it's pepper name), thermostat opens.

Something here is wrong, likely with a sensor or valve.

~psguardian
 

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You have the coil banks up correct??? There was another post with problems like this,I don't know how tondo the links. But he had a bad coil. Spark gets weak or misses when warm. The coil heats up and the internals start shorting out. That might be your problem.....
 

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Discussion Starter · #14 ·
Heres the scoop, sunday, i went to the pick and pull and replaced my whole front end (it was screwed, multiple wrecks), and got a brush guard. in other words i spent a bunch of money on the thing.
Put it all on, ran AWESOME. has been running great since! *knock on wood*
I dont know what i could have done or even touched, i havent posted for a few days figuring it would come back.. but so far so good..
Guess the trooper was just upset i havent been spending much money on it :roll: ill keep yall posted if it comes back..
 
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