2000 Silverado Rough Idle

Please help. I have a 2000 1500 with the 5.3 around 150,000 miles. I would assume that no maintenance has been made to this truck outside the normal oil change.

I was driving it one day and as I was going up a hill the truck seemed to sputter. I thought the transmission was struggling to find the right gear so I changed the fluid. After that it seemed very sluggish. I drove it this way until this recent problem occurred but while searching for this I found out that I may have accidently unplugged the shift solenoids.

One day I walked out and tried to start the truck, it had a rough idle and sputtered until it finally stalled. I can get it to run if I hold the fuel pedal down (around 1500rpm) but once I let off the truck falls to around 500 rpm until it stalls. I pulled the all knowing P0300 code. Random misfire.

Has anyone ever seen this and know to solve it?

I replaced the plugs and still no change.

you should check the fuel pressure regulator for correct pressures

I checked the fuel pressure and it's around 57 psi. I tried to replace the fuel filter but as most of the components on this truck they have a good amount of rust on them.

From my Haynes manual, 57 is in the correct range for this truck.

I kinda think it might be a clogged cat but I can't seem to get the bolts to budge. I know you can check this by observing changes in MAP readings but I can't get the darn thing to idle.

I checked the EGR valve and it seems to be working properly.

Anything else I could check?

I checked the fuel pressure and it's around 57 psi. I tried to replace the fuel filter but as most of the components on this truck they have a good amount of rust on them.

From my Haynes manual, 57 is in the correct range for this truck.

I kinda think it might be a clogged cat but I can't seem to get the bolts to budge. I know you can check this by observing changes in MAP readings but I can't get the darn thing to idle.

I checked the EGR valve and it seems to be working properly.

Anything else I could check?

THE fuel filter does get rusted badly...get some cloth and rap around the fittings, then with a rust /penitrating oil made for this purpose NOT WD-40 let is soak for a few days then try to remove with 2 with wrenches..

to check the converters ,,,,with the exhaust hot loosen the upsteam O2 sensors....then when the pipes cool down fully remove these sensors leaving the holes open....go for a test drive to see if power returns..if so this is an exhaust restriction...could be muffler or converters or the converters broke up plugging up the muffler /pipes etc....

fuel pressure should be 53-62 psi range and on engine off hold with in a few psi for a few minutes...pressures droping rapidly means pump check valve/fuel regulator/injector[s] or some othe leak...

post back with whats up....

I replaced the plugs and still no change.

When you changed the plugs did you also change the wires? I had this code on a broken wire...