hey all. new to yotatech and am happy i found it. lots of info.

Ok so i have a very strange problem im not seeing any answer to. the truck is a 96 3.4l v6 5vz-fe 4x4. a few weeks ago my gf noticed a slight hum coming from my truck. its so quiet that unless its pointed out u didnt hear it. well, over time it got louder. its nothing like an alternator going out, its a very quiet high pitch hum that you only hear when its at idle or low rpm. it does not change with rpm but as far as i can tell it goes away after about 1600 rpm. after about three weeks of it i then had a no start no spark situation one day. after checking fuses and flashing computer i got it to start and get me home (which it was running fine btw)

So heres what i have done since that day. first i started testing all the ignition components. coil, plugs, wires, and cam sensor. i needed to do a timing belt so while i was doing it i just replace the cam sensor. i also replaced plugs and wires (which the wires were a little under specs). i then started it up and again heard the hum.

now in talking with friends (who arent toyota gooroos but decent mechanics) i have heard it could be a hum from having spark but not enough spark. does this sound right to anyone else? I also found an ignitor on the net for $20 bucks so i bought it and threw it in as well (since no one in the world will test these things except toyota and i hate going to the dealer). its still huming and today again i had a no start problem again.

any help is appreciated and im open to ideas.
thanks

 

With these engines you really need to pull your code.

Just to tell you where to start.

If you can get a Factory Service Manual The Diagnostics section is worth it alone

It even tells you how to check your igniter.

You get the noise weather the engine is running or not?

If only when running it could just be something vibrating that goes away as the rpm increases .

Could be a coil in a relay making the noise .

Could be some sort of feed back through your speakers.

Not enough spark is interesting I never heard of that but I learn every day

 

So i went down to the parts house today and picked up a stethoscope since a screw driver wasnt really working for me. i found that this hum is loudest when i put the scope on the valve cover over the driver side all the way front cylinder and goes away as i move from it. it does sounds like an electrical hum for sure.

does anyone know a way to test to be sure im getting the right amount of spark at the end of the plug? if so how and what do i need to do it?

thanks for the help

 

the hum could be bearings in a pulley or idler somewhere. Did you replace everything timing related? the tensioner and idler pulleys? cam and crank seals?
some times fuel pumps can hum as well.