Misfiring and Hesitating

[Malo Hombre]

Thanks to all for the invaluable help of this forum! I have a 2001 3.0, 120k miles, that is hesitating and misfiring. Gas mileage has gone out the window and I'm worried that I have a major problem.

This started after taking it in for an alignment. The mechanic pulled codes and gave me a laundry list of items that needed repaired: Air boot, valve cover gasket, no coolant in radiator and cap missing, exhaust cam sensor, thermostat, and air filter.

First things first, I replaced the radiator cap and filled it with coolant. Then I replaced the airboot and filter. After this, it started to hesitate periodically at low speeds. I read a forum post that suggested cleaning the MAF with carb cleaner, so I gave it a shot. BAD idea! It must have left a residue on the MAF because it would barley run until I found some MAF cleaner at the parts store. At this time I also noticed, at idle, a loud pinging noise like something physically hitting the inside of the case near the adjuster unit.

Meanwhile, my exhaust cam sensor came in and I replaced it. Still no luck, so I took it back to the mechanic. He thought the pinging was a misfire, probably caused by oil in the spark plugs. I pulled the covers and coils. No oil, but I replaced the plugs anyway while I was there.

Next, I changed the fuel filter. Still nothing. With the engine at idle, running rough, I decided to pull of the wire going to the MAF. Low and behold, it smoothed out and ran like a champ! I took it for a test drive and everything was great except that is shifts hard with the sensor unplugged. So, I ordered a MAF from Ebay and hooked it up. Still no luck! ARGH!!!!

I took it to another mechanic. I discovered the first one had overcharged me on the original alignment and he got pissed when I called him on it. The new guy thinks there [FONT='Verdana','sans-serif']IS[/FONT] something physical rattling around in the case, maybe having to do with the timing chain. He wants to charge me $600 to tear it down and find out what is going on.

Any ideas or opinions? I'm not entirely sure I trust that the new mechanic knows what he is talking about. This leaves me with the dealer who want $140 just to look at it.