So, as I've posted in a few other threads, I recently rebuilt my 5.9 magnum engine in my 01 ram.

It's beEn running and driving alright, but its extraordinarily sluggish, has now thrown a code for an evap leak, has a hissing sound (sounds like from the passenger side) when it starts up, but that goes away after a minute. It does get louder upon acceleration for the time it lasts. The blend door flops back and forth before I even go into high gear, just while driving normally. And lastly im going through fuel like nobodys business.

I've replaced my check valves, all the rubber vacuum hoses I can find (the evap system hoses being the exception), the purge valve, blend door motor, vacuum connectors, etc.

I did install a throttle body spacer when I did the rebuild, so not sure if that could be the issue.

All that to say, I'm at a loss for what the issue is. I tried calling near me to get someone to set the fuel sync on the truck, but there's no one within an hours drive,so I haven't done that yet. Even still, i dont think an "off fuel sync" would cause a vacuum/evap leak (code is p0442). Any help would be appreciated. I've dealt with vacuum leaks the whole time I've owned the truck, just a nightmare to find without a smoke machine, which I don't have.

 

P0442 Evap Leak Monitor Medium (0.040) Leak Detected
You need to inspect the evap hoses, Start with the main vac line that comes off the intake(in front of the TB on the passenger side) then trace it back.

 

If you've truly been fighting vac leaks this long and can't afford a smoke machine, make one. Tons of vids on YT -- mostly a steel can and a soldering iron. Still, you'd have to have a MASSIVE vac leak to upset speed density (which is possible)

 

Update: went through all of my hoses, replaced a few that were older, though still appeared alright, for the heck of it. Took it for a drive, same thing. In fact, I took it up some hills, and at 3k rpms, it wouldn't even maintain a speed of 55mph (mind you these are less than a 6%grade). Pull a few things off my dash, etc, everything looked and sounded alright.

Is it possible that the throttle body spacer I installed could be causing this?

 

Probably not, but, the throttle body spacer doesn't do you a bit of good. It's designed for wet-flow systems. Carbs, or throttle body injection. You have multipoint, so, dry flow. TB spacer was a waste of money.

 

Well, I removed the tb spacer, still having the same issue. It will still shift to defrost when accelerating, and will not climb hills on its own in cruise. Still also getting extremely bad mileage, and very sluggish driving, like worse that it was before the rebuild. However, from what I can tell, I have no vacuum leaks. I've not done a smoke text as suggested by one other person, but i don't hear any leaks at all. I'd think with issues like this it'd be a very large vacuum leak.

Still at a loss. May take it and do a vacuum pressure test just to see and go from there, but overall i have no clue whats wrong.

 

Have a look down the throttle body, into the intake manifold. See oil pooling in there? There's your vacuum leak. Common problem on the magnum engines.

 

That should have been addressed with the rebuild.
http://www.hughesengines.com/Index/p...p?partid=27091

 

This shouldn't be an issue as I replaced the plenum gasket when I rebuilt the engine. I even torqued every bolt to spec on that, even if it wasnt "necessary" just because i know that is a common issue. On top of that, im not losing oil, or smoking out the exhaust, so im pretty sure that's not my issue.

 

I would look anyway. Your symptoms align pretty well with blown plenum.