I'm out of ideas, guys. (Truck runs like crap no matter what I do).

[jdyates]

Hey guys, if i start unplugging sensors while the engine is on, shouldn't that noticeably change the way it's running?

I tried:
-Unplugging the o2 sensor (on the driver side header): No change
-Unplugging the IAC (which i also just soaked in cleaner): No change
-Taking the vacuum line off the front of the TB: Idle went higher due to more air.
-Unplugging the EGR solenoid (solenoid is known good, off my brother's burban which ran great): No change

Some of you might know the other thread I had started about the truck dying at WOT and some light throttle conditions. That has changed to:

-Sounding cammed at idle, drops low then comes back up, then drops back down and stays fluctuating.
-bogging down BAD off red lights. It doesn't die, but if you barely touch the gas when a light turns green, it starts surging and you have to give it almost half throttle to get it stabilized.
-and it STILL cuts off when i punch it while in OD (under 1,300rpm, cruising speed when TCC locks up after 35mph), and when it does it, it sounds almost like only ONE cylinder is firing, like a "thump, thump, thump, thump", then suddenly opens up and hauls ass.

I'm honestly stumped and am completely out of ideas.

 

[Vortec Lover]

have you timed it recently?

 

[ChrisAU]

Timing, SPARK PLUGS, fuel pump, in that order.

 

[Vortec Lover]

Timing, SPARK PLUGS, fuel pump, in that order.

yup- I'm going to bet you 10:1 that it is your timing.

 

[95chev]

Hey guys, if i start unplugging sensors while the engine is on, shouldn't that noticeably change the way it's running?

I tried:
-Unplugging the o2 sensor (on the driver side header): No change
-Unplugging the IAC (which i also just soaked in cleaner): No change
-Taking the vacuum line off the front of the TB: Idle went higher due to more air.
-Unplugging the EGR solenoid (solenoid is known good, off my brother's burban which ran great): No change

Some of you might know the other thread I had started about the truck dying at WOT and some light throttle conditions. That has changed to:

-Sounding cammed at idle, drops low then comes back up, then drops back down and stays fluctuating.
-bogging down BAD off red lights. It doesn't die, but if you barely touch the gas when a light turns green, it starts surging and you have to give it almost half throttle to get it stabilized.
-and it STILL cuts off when i punch it while in OD (under 1,300rpm, cruising speed when TCC locks up after 35mph), and when it does it, it sounds almost like only ONE cylinder is firing, like a "thump, thump, thump, thump", then suddenly opens up and hauls ass.

I'm honestly stumped and am completely out of ideas.

Just like the other guys have said, sounds exactly like a timing issue

 

[jdyates]

have you timed it recently?

Timing, SPARK PLUGS, fuel pump, in that order.

Timing hasn't been messed with since I've owned it. Used to run great, then suddenly one day went to complete ****.

In the past few months I've done a COMPLETE tune-up, plugs, wires, cap, rotor, ignition coil, pickup coil, oil pressure switch, and even the oil in it has less than 1000mi.

Still haven't had a chance to check the fuel pump pressure, but it should only be 9-13psi (or close) and I've been told by multiple people that it's unlikely to be causing this stuff. Also, i should mention i NEVER let it get under 1/2 tank, so i know the pump hasn't burned out. I'm not sure if it even sounds plausible to be the pump, since i can floor it and once it gets past sputtering and missing, it hauls major ass with no noises or complaints. If the fuel pump were going out, wouldn't it not be possible to get up to higher speeds? Also, no idiot lights on.

EDIT: Looks like I'll be checking my timing tonight. Thanks for the advice, guys. I would have checked it today in the shop but i had to swap trucks with a friend so i could straighten his steering wheel, and the shop is across town from the school where my truck was.

 

[Vortec Lover]

Hey, the good news is that fixing the timing is dirt cheap!

 

[95chev]

Timing hasn't been messed with since I've owned it. Used to run great, then suddenly one day went to complete ****.

In the past few months I've done a COMPLETE tune-up, plugs, wires, cap, rotor, ignition coil, pickup coil, oil pressure switch, and even the oil in it has less than 1000mi.

Still haven't had a chance to check the fuel pump pressure, but it should only be 9-13psi (or close) and I've been told by multiple people that it's unlikely to be causing this stuff. Also, i should mention i NEVER let it get under 1/2 tank, so i know the pump hasn't burned out. I'm not sure if it even sounds plausible to be the pump, since i can floor it and once it gets past sputtering and missing, it hauls major ass with no noises or complaints. If the fuel pump were going out, wouldn't it not be possible to get up to higher speeds? Also, no idiot lights on.

EDIT: Looks like I'll be checking my timing tonight. Thanks for the advice, guys. I would have checked it today in the shop but i had to swap trucks with a friend so i could straighten his steering wheel, and the shop is across town from the school where my truck was.

It always seems to happen when you replace the cap and rotor lol

 

[jdyates]

Hey, the good news is that fixing the timing is dirt cheap!

To be honest, I have no clue how. I saw the recent write up, but it didn't really make sense to me.

 

[96k1500]

I agree with Chris, timing dont have to be messed with the timing belt stretches, also even tho you dont run it under 1/2 tank dont mean the fuel pump wont go out, like any other sensor or motor on your truck it will go bad with time