I posted here a little while ago about a CEL. I went out and replaced my spark plugs earlier today, which seemed to do the trick at first, until...
On my test run around the block, everything seemed to be going okay. As I was making the last leg of the trip down the highway, I revved up a bit... as soon as the tach hit about 5,400, the engine seemed to misfire, badly. RPMs dropped about 200 or so for a moment then picked back up, hit the same spot and dropped again. After that, it was fine. Heard a faint 'pfft pfft' noise when this happened.
Any ideas? It has done this once or twice before I installed the new plugs, I believed the old ones were simply bad. But I'm not getting a CEL when it happens, just the apparent missing. Unfortunately I'm not much of a mechanic, and I'm at a loss to explain it, now!
That's not all, either. If I have the AC on, the engine seems to run very poorly. At idle, the vehicle trembles noticeably, but when the AC is disengaged it seems to idle fine. If I have AC on while moving, there's a slight tremble in the vehicle. I'm betting that my AC compressor is going bad. Has anyone else experienced this? Any way to troubleshoot this further? Any advice?
Thanks for any help you guys can give.