96 K3500 7.4l Vortec

[Thomas Augenstein]

Not shifting into OD with popcorn backfiring.
-Knock sensor one low input (bank1)
-Camshaft position sensor A

I am in the construction industry surrounded by $40,000+ trucks and here I am in this.
I don't want to be the broke guy with an old junk truck, I want to be the eccentric guy who likes the old gems of yesterday.

Sputtering on start up, misfiring under a load. (Note)Transmission shifting correctly.
Found a melted knock sensor one wire so I repaired the damage and then replaced
-Bank 1 Knock sensor
-plugs
-Wires
-cap
-coil
-cam pos.sensor
-crank position sensor
-rotor button

It ran great for the first hour, then backfiring and shifting issue.
The two codes above were triggered.

I am going to check the timing.
Maybe 20,000 miles on rebuilt motor.
Any insights would be appreciated. I have changed many parts over the years and still know very little.

 

[Schurkey]

BIG question: Does it not go into 4th gear, or does the converter not lock up?

I bought a '97 K2500 with 7.4. Horrible misfire on #8, converter clutch wouldn't engage.

Turns out, the computer refuses to engage the converter clutch if it detects misfire. I fixed both problems by replacing the #8 spark plug that the previous owner broke while installing. Yeah, a new spark plug fixed my transmission.

You can "check" the timing, but since it's not adjustable you'll need computer reprogramming to make it right if it isn't already. Or the computer failed and has to be replaced. You may have to turn the distributor to get the cam sensor and the crank sensor to align their signals to the computer.

WHAT IS YOUR FUEL PRESSURE when the engine is running poorly?
How old is the fuel filter?
WHICH cylinder is misfiring?
Did you align the cam sensor (distributor) to the crank sensor as specified in the service manual? As long as you have the scan tool connected to verify cam sensor/crank sensor alignment, what else does the data stream show?
DID YOU CLEAR THE CODES after all the parts were replaced, and the wire harness to the knock sensor repaired, but BEFORE running it for that "first hour"?

 

[454cid]

How many miles on the distributor? The gear is known to wear.

 

[Thomas Augenstein]

How many miles on the distributor? The gear is known to wear.

Probably 200,000 I have no way of knowing if it was changed with the rebuild, but I suspect not.

 

[Crazydavez28]

Not shifting into OD with popcorn backfiring.
-Knock sensor one low input (bank1)
-Camshaft position sensor A

I am in the construction industry surrounded by $40,000+ trucks and here I am in this.
I don't want to be the broke guy with an old junk truck, I want to be the eccentric guy who likes the old gems of yesterday.

Sputtering on start up, misfiring under a load. (Note)Transmission shifting correctly.
Found a melted knock sensor one wire so I repaired the damage and then replaced
-Bank 1 Knock sensor
-plugs
-Wires
-cap
-coil
-cam pos.sensor
-crank position sensor
-rotor button

It ran great for the first hour, then backfiring and shifting issue.
The two codes above were triggered.

I am going to check the timing.
Maybe 20,000 miles on rebuilt motor.
Any insights would be appreciated. I have changed many parts over the years and still know very little.

Check your rotor again. I have had the center tab break off and cause a misfire. Cheap crap off Amazon didn't last.

 

[Thomas Augenstein]

BIG question: Does it not go into 4th gear, or does the converter not lock up?

I bought a '97 K2500 with 7.4. Horrible misfire on #8, converter clutch wouldn't engage.

Turns out, the computer refuses to engage the converter clutch if it detects misfire. I fixed both problems by replacing the #8 spark plug that the previous owner broke while installing. Yeah, a new spark plug fixed my transmission.

You can "check" the timing, but since it's not adjustable you'll need computer reprogramming to make it right if it isn't already. Or the computer failed and has to be replaced. You may have to turn the distributor to get the cam sensor and the crank sensor to align their signals to the computer.

WHAT IS YOUR FUEL PRESSURE when the engine is running poorly?
How old is the fuel filter?
WHICH cylinder is misfiring?
Did you align the cam sensor (distributor) to the crank sensor as specified in the service manual? As long as you have the scan tool connected to verify cam sensor/crank sensor alignment, what else does the data stream show?
DID YOU CLEAR THE CODES after all the parts were replaced, and the wire harness to the knock sensor repaired, but BEFORE running it for that "first hour"?

Check your rotor again. I have had the center tab break off and cause a misfire. Cheap crap off Amazon didn't last.

Thank you for all the info, I'll start checking things. Good to know about the shifting being connected to the misfiring. I repaired the knock wire first, but was wondering since I am still getting the code if it may have shorted out or is that possible?

 

[someotherguy]

If it's the original plastic body distributor at 200K it's worn and is highly suspect. If you remove the cap and turn the rotor by hand either direction until it pops up with the helical movement of the distributor gear.. try moving the rotor from side to side. If it moves side to side, replace the distributor. It's toast. Make two very distinct marks before you remove your original: rotor position, and distributor position. Install new one as close as humanly possible to same marks, so you can get it running. Then fine-tune cam retard angle using a scanner that can read that data, hold RPM's at least to 1,000 for good reading, adjust distributor until it's within +/- 2 degrees of zero.

Richard

 

[Thomas Augenstein]

BIG question: Does it not go into 4th gear, or does the converter not lock up?

Stays in third and doesn't shift out, occasionally it shifts fine, but backfiring at high rpm.

I bought a '97 K2500 with 7.4. Horrible misfire on #8, converter clutch wouldn't engage.

Turns out, the computer refuses to engage the converter clutch if it detects misfire. I fixed both problems by replacing the #8 spark plug that the previous owner broke while installing. Yeah, a new spark plug fixed my transmission.

You can "check" the timing, but since it's not adjustable you'll need computer reprogramming to make it right if it isn't already. Or the computer failed and has to be replaced. You may have to turn the distributor to get the cam sensor and the crank sensor to align their signals to the computer.

WHAT IS YOUR FUEL PRESSURE when the engine is running poorly?
How old is the fuel filter?
WHICH cylinder is misfiring?
Did you align the cam sensor (distributor) to the crank sensor as specified in the service manual? As long as you have the scan tool connected to verify cam sensor/crank sensor alignment, what else does the data stream show?
DID YOU CLEAR THE CODES after all the parts were replaced, and the wire harness to the knock sensor repaired, but BEFORE running it for that "first hour"?

 

[Thomas Augenstein]

BIG question: Does it not go into 4th gear, or does the converter not lock up?

I bought a '97 K2500 with 7.4. Horrible misfire on #8, converter clutch wouldn't engage.

Turns out, the computer refuses to engage the converter clutch if it detects misfire. I fixed both problems by replacing the #8 spark plug that the previous owner broke while installing. Yeah, a new spark plug fixed my transmission.

You can "check" the timing, but since it's not adjustable you'll need computer reprogramming to make it right if it isn't already. Or the computer failed and has to be replaced. You may have to turn the distributor to get the cam sensor and the crank sensor to align their signals to the computer.

WHAT IS YOUR FUEL PRESSURE when the engine is running poorly?
How old is the fuel filter?
WHICH cylinder is misfiring?
Did you align the cam sensor (distributor) to the crank sensor as specified in the service manual? As long as you have the scan tool connected to verify cam sensor/crank sensor alignment, what else does the data stream show?
DID YOU CLEAR THE CODES after all the parts were replaced, and the wire harness to the knock sensor repaired, but BEFORE running it for that "first hour"?

 

[Thomas Augenstein]

I didn't realize the cam and crank sensors had to be aligned, they both fastened into place without any engine rotation. I remember seeing mechanics turning the distributor to dial in timing, I was wondering if that needed done, maybe from slightly off timing on reassembly after engine rebuild