2005 4x4 4cyl issues

Hello all,
Have a couple of issues with my taco and would like to get some input. It's an 05 4x4 4cyl 5spd with 95k on it.

First issue: At start up I get an odd noise under the hood and can't locate it. It sounds like a whirring/spinning noise. Thought it may be an idler pulley, to serp belt off and spun all of the pullys and they spun fine with no noise. Put a steth scope on it while running and it definitely sounds like its coming from the front of the motor, but can't pin point exactly where its coming from.

Second Issue: Constant engine stumble. Does it pretty bad at start up, but gets better as the truck warms up. Never seems to fully go away though. Drives fine, but when I stop at a light it's minimal, but still there. Changed spark plugs and put fuel system cleaner through and it still does it...

Any help would be greatly appreciated!

 

Anyone??

 

Check rubber hoses for brittleness or vacuum leaks. Make sure all the MAF pipes are tight.

IDK but I'd pull the plugs or at least make sure they're tight (make sure you used a dab of Loctite Anti-seize on the plug threads or you'll be sorry)

Clean the MAF wire with Radio Shack COLOR TV Tuner cleaner (just a few shots) to clean the wire.

I'm thinking it might be an idea to look for a spare Alternator.


I'm wondering if a spare coolant temp sensor might not be handy to have around, too.

At your mileage maybe the 02 sensor(s) should be changed.

 

Thank you for the ideas Steve, I will look into them over the weekend and see what I may come up with.

 

By any chance do these engines have timing chain problems b/c the ac, steering pump, alt are not making the noise. Sounds is coming from the middle front area of the engine when I have the scope on it.

 

no check engine lights?

 

Sorry but I'm fairly new to this engine and frankly haven't had to really look at it.

I'm leaning towards the 02 sensor(s) on your exhaust and whatever the noise at the front of the engine I'm sorry I can't help.

 

Does the noise occur at cold start up and last for about 10 seconds, then stop when the RPM's start to come down? If so, you're hearing an electric air pump that's forcing air into the exhaust manifold to help with catalytic converter warm-up. It's normal.

As far as running rough . . . my truck feels like it's running rough at idle too (~650 rpms). When I bought my '06 last year (17,800 miles) I had the same concerns so I changed spark plugs, PCV valve, cleaned MAF/temp sensor, cleaned throttle body, checked every single hose and connection, changed coolant, ran a tankful of Techron cleaner, and replaced the intake air filter. I only use Mobile 1 synthetic oil and only use Toyota filters.

Everything I did had absolutely no effect on the idle vibrations, so I've just lived with it for the last year. It doesn't sound like the engine is missing or anything, which you can check by bending down near the exhaust tip and listening. I've just chalked it up to the 4 cyl. being naturally unbalanced, despite Toyota's attempt to offset with balance shafts.