Surging and low rpm stumbles

[mockspeed88]

94 k2500 5.7. So it is still stumbling and surging. Not as bad but it's still there. Runs like crap before 2500rpm, then it runs like a Nascar. Stalls occasionally going from drive to reverse. Stumbles off idle. Surges 50-100rpm at idle.

What's new:
Duralast gold distributor
Napa premium wires
Temp sensor
Iac
Map
Ngk v power spark plugs
Shorty headers
Cat and cutback
Ac delco o2 sensor
Vacuum lines
Throttle body rebuild
In tank drop in pump
I replaced all the fuel lines with a nylon type line kit
It idles around 300-400 rpm in park, drops down to about 150 in gear
Also just did the timing chain
Egr
Pcv

 

[Schurkey]

94 k2500 5.7. So it is still stumbling and surging.

Connect a scan tool, find out what the computer is trying to tell you. Verify ALL sensors and their wire harnesses, verify ALL computer outputs and their wire harnesses.

Verify fuel pressure.

Is the base ignition timing set properly? Does it advance when you plug the timing connector back together?

Cat and cutback

What is a "cutback"???

Also just did the timing chain

Did you degree the cam? What is the cranking compression?

 

[mockspeed88]

So I replaced the icm, map, egr solenoid, with acdelco parts. Also went to the treasure yard and found a much lower mile tbi 350 and I pulled off the tbi unit. Truck runs much better now. It just has a slights stumble at very low throttle before say 1500 rpm. I put shorty headers on the truck so I am going to put the O2 from the y pipe to the headers

 

[mockspeed88]

Well truck has a rough idle still in drive. Stumbles a little below 1500, idle bounces in gear between 200-400ish

 

[thinger2]

94 k2500 5.7. So it is still stumbling and surging. Not as bad but it's still there. Runs like crap before 2500rpm, then it runs like a Nascar. Stalls occasionally going from drive to reverse. Stumbles off idle. Surges 50-100rpm at idle.

What's new:
Duralast gold distributor
Napa premium wires
Temp sensor
Iac
Map
Ngk v power spark plugs
Shorty headers
Cat and cutback
Ac delco o2 sensor
Vacuum lines
Throttle body rebuild
In tank drop in pump
I replaced all the fuel lines with a nylon type line kit
It idles around 300-400 rpm in park, drops down to about 150 in gear
Also just did the timing chain
Egr
Pcv

 

[thinger2]

Keep in mind the factory tach doesnt read 0 to 1000 rpm.
It reads 500 to 1000 rpm.
This is my 94.
Look at the difference between 0 to 1000 and 1000 to 2000
So you arent idling at 250.
I dont think a small block chevy will ever idle at 250 and still run.
Doesnt make a whole lot of difference in the big picture.
A miss is still a miss.
But the idle might actually be pretty close.