94 1500 5.2 stumbling idle, dumping fuel

[Nealuss]

Ok, so a bit of a backstory here...

The truck was down for almost a year with a busted rear diff that I couldn't make my mind up on and couldn't really afford to fix. Finally got it rebuilt about 3 months ago and got it back on the road. To my surprise it didn't really have any hiccups at first. I had seafoam in the tank when i parked it and I cranked it every now and then to keep the juices flowing.

About 1/2 tank through after getting it back on the road it started to sputter when it got to temp. I figured maybe bad gas so I ran about 2 tanks of ethanol free 89 through it and it seemed to get better, but wouldn't go away completely. It was also stumbling on startup a bit so I checked fuel pressure and it was perfect. Never fluctuated at all and jumped right up to 40psi at the rail as soon as it primed.

Fast forward to yesterday. I was getting in it to make a short trip to the store and as soon as I fired it up it idled like it had a massive cam in it. It has pacesetter long tubes and no cats so I could see and smell the fuel smoke coming out of the exhaust very clearly. With a little throttle it would smooth out but still tons of unburnt fuel in the exhaust. Where do I start here? Any body have advice?

 

[tthompsr]

sounds like a injector, I had it happen to mine. check your plugs to see which cylinder is acting up.

 

[Nealuss]

That's the next step I think. I'm pretty sure I have a vacuum leak somewhere too but just haven't had time to mess with it. Funny thing is when I went out the day after posting this thread it ran fine. I expect there is still something wrong, though. That type of problem isn't a fluke.

 

[Nealuss]

Just in case anyone comes across this and wonders what happened...my issue ended up being the plenum plate. Not sure what happened but there was a leak with the Hughes plenum plate I installed a while back. We are going all in this time and resealing everything including valve stem seals, properly deleting the egr, and doing some modification to the stock kegger intake manifold. Moral of the story, your first instinct is usually right. I thought it sounded like an intake leak but didn't want to believe it.