95 350 tbi dies under load

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Hi all. I got a 95 step side a few months back and have been slowly chasing dumb little issues it has.
It was swapped to the 350 tbi by previous owner, and has been giving me a rough time essentially since I got it.
The main issue I’m having is that when it is under load, it’ll spit sputter and die.
It was having a rough / weird idle but I seem to have gotten that under control.
I’ll include a list of everything that has been replaced so far.
Most recently I replaced the coolant temp sensor, switch, and thermostat, and since doing that, it’ll now jump straight to high temp as soon as the truck starts, with 0 pressure in the radiator hoses. Threw caution to the wind and stuck my finger in the radiator to test coolant temp and it’s Luke warm at best. The minute the thermostat opened up, truck dies.
My assumption on this is a bad water pump, but given this is my first Chevy venture I’d like some input from people who know these trucks well.
I love this truck, even if it’s sat more than I’ve driven it. I’d really like to get him back on the road.
Replaced parts:
Fuel pump, filter, and relays
EGR and EGR solenoid
MAP Sensor
TPS
Plugs, wires, Distributer cap
Coolant temp sensor and switch
Thermostat
 

GMCTruck

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It sounds to me like you may have the wrong coolant temperature sensors/senders. The coolant itself can't heat up immediately after startup. The coolant temp sender for the gauge goes in the drivers side block. IF the wire is grounded, the temp gauge will go to maximum. The coolant temp sensor for the computer is next to the thermostat housing. Is it possible you mixed the two up?
 

Rustjunky67

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It sounds to me like you may have the wrong coolant temperature sensors/senders. The coolant itself can't heat up immediately after startup. The coolant temp sender for the gauge goes in the drivers side block. IF the wire is grounded, the temp gauge will go to maximum. The coolant temp sensor for the computer is next to the thermostat housing. Is it possible you mixed the two up?
This brings to mind an issue I've had but not addressed as of yet.....
My truck runs normal operating temp but as soon as you switch the key OFF, the temp on gauge rises immediately up to higher ranges usually all the way.....
Any idea what causes this?
 

tpass

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What was in the truck before the 350? Would the ECM need re-programming?
 
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What was in the truck before the 350? Would the ECM need re-programming?
It was the 305. I had taken it to a mechanic for this issue, and he said ecm, replaced it and issue still persisted. So he swapped it back. It’s my understanding that whoever did the motor replaced the ecm.
It’s a really frustrating situation, to say the least. I’m going to tinker with it this weekend some more. And if all else fails, eventually I’ll do an LS Swap
 

Schurkey

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Hi all. I got a 95 step side
It was swapped to the 350 tbi by previous owner,
That can't be good.

Most recently I replaced the coolant temp sensor, switch, and thermostat, and since doing that, it’ll now jump straight to high temp as soon as the truck starts, with 0 pressure in the radiator hoses.
What "switch"?

Clearly the temp gauge has problems.

My assumption on this is a bad water pump,
No idea how you'd come to that conclusion. The water pump doesn't affect gauge accuracy.

Replaced parts:
Fuel pump, filter, and relays
EGR and EGR solenoid
MAP Sensor
TPS
Plugs, wires, Distributer cap
Coolant temp sensor and switch
Thermostat
Were any of these parts TESTED before being replaced?

What is the fuel pressure?

How old is the distributor rotor?

Connect a scan tool, verify ALL sensors and computer outputs.

This brings to mind an issue I've had but not addressed as of yet.....
My truck runs normal operating temp but as soon as you switch the key OFF, the temp on gauge rises immediately up to higher ranges usually all the way.....
Any idea what causes this?
WHAT VEHICLE???

Aftermarket mechanical gauge? Totally normal.

It was the 305.
Did they install 5.7L fuel injectors?

And if all else fails, eventually I’ll do an LS Swap
Going from difficult to REALLY difficult?
 

tayto

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what is the broadcast code on the PCM. When you changed the PCM did you swap the memcal (chip)?
 
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