From running perfect to sputtering

[Billingstitan]

1989 K1500 5.7/350 — stock

Had my old truck running great for at least a year after engine swap, new fuel pump/filter, new TBI leads, TPS, distributor, plugs, etc.

Sitting at the dump, unloading some brush w the truck at idle, and I heard the pitch of the engine change.

Driving out of the landfill, it still runs good, but its suddenly got kind of a sputter, and almost what feels like a miss.

When I get on the gas, power def lacks, and there’s a hesitation.

Feels like it’s going to die sometimes at stoplights, but it doesn’t … idle just kinda stumbles, then catches, then stumbles.

Checked my connections, everything looks solid.

It runs like the timing is off — it is not.

I gotta think something ‘went out’, rather than a tuning issue, due to the suddenness of how the problem manifested.

Y’all got any wisdom to share? I replaced the entire ignition system when I swapped the engine in 2020.

I’m scratching my head here, guys …

 

[User_name]

Well start with your basics.
What's the fuel pressure? Should be 12-15 psi for best operation.
What's the cap, rotor, plugs, and wires look like?
Any vacuum leaks?
Are the injectors spraying in a nice, even cone pattern?
Any codes?

 

[F4U-1A]

Sputtering? Me, my Wife, my dog, Its all Good, Just fooling around.

 

[Schurkey]

Connect a scan tool, find out what the computer is trying to tell you.

Verify fuel pressure.

 

[Jeepwalker]

Any codes?
I'm with Shannon400, go over the basics. With special emphasis on:
-Vacuum leak
-Cracked spark plug
-Bad spark plug wire
-Ohm out the temp sensor (cold and hot).

On an 89 you're not going to get a lot of info on a scan tool. But looking at the O2 sensor could help out, and you can see what the temp reading is cold and hot.

 

[Schurkey]

On an 89 you're not going to get a lot of info on a scan tool.

Common mistake.

EVERY sensor can be interrogated.
Computer outputs such as AIR solenoid, EGR solenoid, IAC motor, torque converter clutch, etc. can be viewed.

Some bi-directional control is permitted.


See posts 14 and 15:

94 k2500 no low end power and horrible fuel mileage - Automotive Forums .com Car Chat

94 k2500 no low end power and horrible fuel mileage C/K

www.automotiveforums.com

 

[Billingstitan]

Well start with your basics.
What's the fuel pressure? Should be 12-15 psi for best operation.
What's the cap, rotor, plugs, and wires look like?
Any vacuum leaks?
Are the injectors spraying in a nice, even cone pattern?
Any codes?

I drive a semi, so today was the first chance I had to work on this ******* vixen.

Fuel pressure was spot on, both w engine running and just turning the key. I don’t know if I’m incompetent, but that was kind of a messy job. Love using those metal wrenches as I’m in a growing puddle of gas, lol.

Checked my vacuum lines, all look good.

Changed out the MAPS sensor; installed a new distributor w new cap, rotor and ICM.

Plugs and wires wires are fairly new (mayb 10k amd 3 years).

Injector spray pattern looks good.

I am not sure what the hell else to try? Runs better at low speeds, but lacks power in higher gear/speed, kinda shudders a bit, misses …

My gut says ignition — but last time it acted up my gut said ‘fuel pump’, and I replaced all that only to find it was the coil . So my gut is not a reliable source, lol.

Any ideas? Should I post an updated thread as an update to ask the larger community — I hate to be a pest.

 

[97Burban57]

Bad O2 sensor?

 

[1997]

post #2, any codes?

OBD1 can set codes without the check engine light coming on.
easy to check, might help you narrow done what to look at.

 

[Schurkey]

Runs better at low speeds, but lacks power in higher gear/speed, kinda shudders a bit, misses …

Plugged exhaust?



Still need that scan tool.