I am once again working on my brothers 2002 Neon SE (auto). His "very detailed" description wasn't very helpful, but included almost stalling at lights and using a lot of gas. So after driving it, I noticed the idle was a bit rough and shakey. Checked the engine mounts and replaced 3 of them (not the tranny one) and adjusted the idle up a bit. Seemed fine.

So I drove it about 30 miles and gave it back to him. A few days later he called and let me know it was doing "the same thing as always".

So, I picked it up again. I noticed a few issues this time.
1. Valve cover Gasket Leak
2. After it idles about 10 min. there is a noticeable knock (sounds like sticky valves to me)
3. When it downshifts from 2nd to 1st, or I should say, as it SLAMS from 2nd to 1st, there is a nice loud clunk and the engine drops in revs for a moment.
4. Engine seems to strain while idling in drive. Runs fine in Park or neutral.

Once going, it drives fine. But I should mention a few of the repairs it has had over the last few years. It now has new plugs, wires, MSD coil pack, engine mounts, trans control solenoid, brake master cylinder, brake hoses, idler pulley, and some suspension components.

All the fluids have been changed frequently and are currently full, and there is no oil on the spark plugs.

So.... What is causing the trans issues? and is there any adjustments I should make to the valves when I fix the valve cover gasket?

Sorry for the long post, but I wanted to be descriptive.