56.3 runs rough when cold & WOT

[dmarty]

No bolts and no snap ring as far as I can see. Looks like a sealed unit to me. The MAF has 3 honey comb cells that are dark and I can't get them clean. Is that a problem? The IAT was at normal op temp, so I think it's ok. Tried it today cold and it was near ambient temp. MAP seems ok too. I'm gona run it for a while and let the Sea Foam work. I checked on the price of injectors and they're not cheap. I may pull em and soak em and see if it makes a difference before dropping the big bucks.

[dadsworktruck]

go back and check your intake gaskets , my 5.3 ran awlful in cool weather,i snugged up the mounting bolts and it fixed mine.

[dmarty]

It probably woudn't hurt to check the bolts, but I sprayed water around the intake gasket after starting it cold and didn't get any steam out the exhaust or change in RPM.

[dmarty]

The WOT cold misfire continues and is driving me nuts!!!! To update, I’ve done the following:
Replaced intake gaskets and injector O-rings.
Replaced plugs and wires.
Replaced fuel and air filters.
Replaced PVC valve.
Replaced both upstream O2 sensors.
Cleaned MAF twice with MAF cleaner.
Cleaned injectors with Sea Foam and ran several cans of Sea Foam through gas tank.
Removed TB and cleaned thoroughly with TB cleaner.
Measured fuel press and is constant at 57 psi @ WOT (same reading with two different gauges).
Fuel press leaks down to 14 psi overnight.

Been doing a lot of highway driving lately and set the following code while cruising, but I did not detect a misfire at the time and the engine was fully warmed up. Only set it once and the MIL light went out after 200 miles. Engine continues to start fine and run normally when warm.

P0300: Random Multiple Cylinder Misfire Detected
TPS: 16%
MAF: 3.71 lb/min (28.1 g/s)
Load: 12%
ECT: 193 F
RPM: 2258
#1: closed loop
#2: closed loop
MAP: 12.4 in/hg
LT Trim #1: 4.68
LT Trim #2: 2.34
ST Trim #1: 2.34
ST Trim #2: -2.34
Vehicle Speed: 78 mph
This looks normal to me, but maybe I’m missing something.
Also set code P:0336 Crankshaft Position Sensor, under cold WOT conditions one time, but I was stupid and erased data without saving it and it hasn’t happened again.
Any help, suggestions or comments would be greatly appreciated. Thanks!!!!

[dmarty]

Not that anybody cares, but I finally found the problem. It was the CKP sensor. Got to the point of throwing parts at it and tried the crank sensor as I had one code for it early on, but thought it was a result of all the poping and backfiring that was going on. Sometimes I get lucky!

[usmcchevy]

Glad ya got it fixed.