Hi, I just replaced the engine in my Grand Am
a few days ago, and am currently running into some issues. The first day I got it running, everything was fine. I didn't run into a single problem. But the second day, it started acting funny. At first, the only issue was that every so often while accelerating even slightly, the engine would sputter just a little, as if it was running out of gas, and then it would be fine for a while.
Then today, I went to drive it again, and it was absolutely fine for a while, no sputtering whatsoever. It eventually started sputtering again, and started happening more and more often. It started sputtering even when I was idling or decelerating. The sputtering wasn't very intense at all though, it was really light and was only for a second.
Then as I'm turning into the grocery store, my engine just starts making this really low and loud rumbling, and it accelerates extremely slow. It sounds like my entire exhaust just fell off at the engine. When I parked and opened my hood, I was blasted with exhaust fumes. I checked at my muffler, and there's barely anything coming out of it. Also, besides the loud rumbling, there's something else that just sounds off about the engine, but I'm not sure how to describe it. I would venture to say it sounds like what I would assume is one or more of the pistons not firing.
The car itself is a '99. The new engine in it is the same as the previous (3.4L), but the new one is an '03.
My car had been sitting in my garage on jack stands without the engine in it for the last 7 months.
Also, after the rumbling started, my car overheard fairly quickly.
After some research, my best guess is that the fuel injectors are clogged, but I want better opinions on the problem before I go tearing this engine apart.