wierd engine noise - need some help

i have an 01 3.4 liter. i noticed a weird noise comming from my engine yesterday. it usually only happens when the engine is working (ie high gear in low rpm's or climbing a hill)

a friend of mine said it sounds like the tac/speedometer is rattling, but both gauges look fine with no weird movement.

i don't seem to notice a change in engine performance, but it is rather loud and i'd like the peace of mind... y'know?

 

Your friend could be right about the speedo cable rattling, although I'm unsure on how to check for that, but I'm sure someone will chime in about this. Also, does it sound like a loose or broken exhaust manifold? It also produces a rattling sound under power.

 

Are you sure it's not preignition (pinging)? That would happen under load or when lugging at low rpm, particularly if the 02 sensor or MAF wasn't functioning properly. Is your Check Engine light on? Try using premium gas and see if it still happens.

 

i think pinging is a good word to describe the noise.
my check engine light is on, the code said something about the engine running lean, and cat something.

i thought it was a vacuum leak, as one of my caps on the intake manifold fell off. but, now it's closed off and the light is coming back.

i've read about cleaning the MAF, so i'm going to do that... what should i do about a faulty 02 sensor?

 

I just experienced the same problem. Cleaning the MAF fixed it and made a world of difference in the way the pickup runs. If that doesn't fix the problem and turn out the CE light, you may need to replace the sensor located in front of the catalytic converter. From what I read it will run you anywhere from $50 to 150, depending on your model year. A couple of us have found that Toyota is very competetive on the price and beats the price of some of the "discount" parts places.

 

You mentioned caps on your intake manifold. Is it the stock intake system or have you gone to a high performance system or a high-flow air filter? If so, I can almost guarantee that cleaning off your MAF will fix the problem. Be very careful how you clean it off. Don't touch the sensor or you could damage it. Spray it off with electronic parts cleaner (see the thread about O2 sensors). Also make certain you don't have any air leaks in the intake system after between the MAF and engine. That might cause a faulty reading and a lean condition as well.

 

I have the stock TRD K&N intake. i'm going to try cleaning off the MAF today, and if that doesn't work, i'll move on to the sensor. i'll let y'all know how it goes.

 

That there is your problem. I should have guessed that you would have something like that from your first post. I bet you a shiny penny that the oil on the K&N gunked up your MAF sensor and is giving you all your problems. The link below is how to properly clean the MAF sensor on a 3.4L V6.

http://www.4x4wire.com/toyota/maintenance/tacoma_4runner_30k/maintenancep5.html#maf

or

http://4runners.org/writeups/throttle/index.html

One thing I have to add, never ever use a q-tip or anything like that to clean the MAF sensor, just buy some CRC brand electrical contact cleaner like the can below:

 

crc carb cleaner works good too...MAKE SURE YOU LET IT DRY lol with either one...clean it on a day where you dont plan on going anywhere and just let it sit off the truck for the day you dont want to start the truck if there is any chance of it still being wet..both products obviously dry pretty fast but I'd rather spend little extra time watching tv to be sure it was dry then start it early and hurt something........you guys notice i use more words than nessisary to explain something? no idea why...it annoys me lol

 

I actually did mine while the truck was running, the way I used to clean the carb on my old Ford pickup. I just made sure I ran the engine until it was all dry and left no puddles of carb cleaner in the intake tube. It fixed the problem and the CE light is out and the pickup runs like a top now. However, carb cleaner will eventually soften plastics, so I go along with "Humanoid"'s recommendation for the electronic parts cleaner. I'll use that stuff next time.