Toyota Repair: 99 3RZFE Pre-runner - very rough idle, air intake hose, vacuum leaks

Question
Hi Tim,
I'll try to be brief - upon starting my truck this afternoon to go home, I noticed it lurching as I was backing out of my parking spot, which told me it was running rougher than usual. This old gal has 235K miles, but something was wrong. I drove a little way hoping it would smooth out, but then I pulled over and popped the hood. As I got out I could smell gas. Under the hood, no hissing from vacuum leaks, no disconnected vacuum hoses, nothing obvious. Got back in and started to limp home but wasn't sure I'd make it, so I went around the block. Pressing the accelarator made it stutter worse until higher rpm's were reached, but very little power (torque). It's an auto trans and the engine stumbles badly at a stop while in gear. Putting it in neutral keeps it from stalling. The check engine light has been on for most of the 2 yrs I've owned the truck. The longest I managed to clear it was after removing and cleaning up the EGR. Today, the check engine light was flashing. I stopped by a local mech. who pulled the codes: 440 (the one I've always had) and I think 446 and 171 (something about lean fuel mix). He thought it is a bad plug or coil pack... I'd love a second opinion. Hope I provided enough symptoms and context.

Thanks for your time,

Thomas

Answer
Thomas,

I need more specifics to analyze this problem.

A vehicle with that many miles could have a number
of issues. If I was at the truck and drove it then
it would be fairly simple, but we don't have that luxury.

The first thing to do is a tune-up !I don't know when that was last
done ! My description of a tune-up is different than
installing plugs and an air filter and driving away.

The plugs must be removed and each inspected to look for variable
differences. Each plug wire must be inspected closely for cracks
or signs of spark jumping to ground. All other ingnition components
must be inspected closely. The rubber air intake hose from the air filter housing should be removed and inspected for cracks. ALL vacuum lines should be closely inspected for cracks or looseness.

The air filter should be inspected.
All connections to the sensors should be inspected.


This problem could be caused by a dirty aluminum intake. The hose from the air filter to it must be removed and a full can of carb/intake cleaner sprayed in there while the throttle is held open.
(engine not running)

Tim