I have my 89 4 runner 3vze that I have had for over 12 yrs. Something I need advice on is where to start attacking this issue and if anyone else has had this problem? When my truck is idling and has the dash lights on, stereo and headlights everything dims to about 50% of normal full power. The dimming is in the headlights and console lights. If I rev up the engine to 2 on the rpm or drive it once I pass 2 on the rpm the console lights go up to 100% and the headlights brighten. When I get up to speeds around 60-70+ mph the dash lights very slightly flicker, not off and on but you can see the power change, and you see intermediate flashes of the brake, battery and back door lights on the dash as if the truck was loosing power. There is no noticeable power change in performance just the flickering of the dash lights.

-So is this a bad alternator?

I checked my spark plug wires to make sure none of them had cracks and or were not grounding out on any metal or melted anywhere. Also they are relatively new cables about 3 oil changes ago.

-Could my distributor cap be bad?

I haven't changed it in probably 2 yrs because when I changed my plugs and cables last the contact on the cap looked fine.

-Any other suggestions on where to attack this issue?

This problem was getting really bad five months ago but my radiator cracked from age and my water hose that goes through my throttle body was leaking on top of my engine pooling water over the knock sensor. Once I changed the hose and the radiator and cleaned up the knock sensor connectors the problem went away but is now back.... not as bad might I add. Any input would be great.

 

sounds like an alternator.. or really crappy ground connections. or connections to battery and/or alternator. Take off the connectors, clean em up and see if it helps

 

Auto parts stores such as Autozone offer free charging system testing.

 

I've seen folks pull the battery cable while the truck is running - if it dies, the trouble is the battery.

I've also heard that can short out your computer, though.

 

My money is on the alternator brushes. Check your connections as well.

 

If the car dies when you pull the battery cable the trouble is the alternator. not the battery.

 

I have seen this before a few times and it was the battery shorting out. The easiest way would be to take a battery terminal off while its running and if it stops flickering then replace battery. If not replace alternator.

 

lol I totally spaced on the battery possibility. Well an update on the status... in 2008 when I was de-greasing my engine I started my truck up to soon and shorted out that alternator... so it was either a $79 alternator or a $139 one from Reibes. I bought the $139 lifetime warranty one... glad I kept the receipt. Dropped the new one in and tested my battery, power problem eliminated. Also thanks for the pointers, will definitely help in the future for trouble shooting.