Vibration issue

I feel dumb now but: in case anyone was wondering I fixed my issue. Turns out my spark plugs were waaaay too old and the electrodes on all of them were concave. So I was actually having issues with bad ignition (without a CEL), with vibration at highway speeds and hesitation on initial acceleration at speed along with dips in power during heavier acceleration.

I put in new plugs and now the truck drives like a dream! No more power-band issues on acceleration, no more shuttering / hesitating when in overdrive, and no more vibrations at highway speeds felt through the floorboards.

If you have strange highway speed vibrations don't overlook spark plugs as silly as it sounds.

edit* To be clear the main issue I had felt like the driveshaft was locking up, or something in the suspension was loose when I first pressed the pedal while the RPMs were low and I was cruising. So I was chasing many driveline / suspension fixes as that's what it felt like to me. In the end the plugs were the actual issue so consider checking them if you haven't yet.

 

Pictures of the plugs?

Also curious what you mean by concave... The dual ground electrodes have a curved shape to them at the tips.

 

I already threw them out before taking a photo, but to explain: Looking at the new plug the electrode (center post) was a perfect cylinder. My old plugs they had small rounded sections lined up with the curved outer ground posts, so they had an out of spec gap since the electrode was worn on both sides.

This isn't my plug but it basically looked like this:



Though mine were rounded on the sides and the top of the center electrode was still fairly flat.

Someone else's photo but this is how the new plugs look:

 

+1 for the rear drums and shoes. My primary vibration was caused by old drums/shoes.

 

never would of guessed plugs

glad Taco is running smoothly!!!!

QQ
did u replace with NGK's? or that same multi-electrodes type?

(heard bad things about those multi ones)

 

Replace them with the recommended plugs- for a 3.4l that's dual electrode plugs. Not sure what bad things you're talking about, but I have regularly changed my plugs and have not had a single issue with them in 20+ years.

 

A firm^^^^^
i had no idea those were 'recommended'

had a customer with new Vette.....(this was 10yrs ago think was C4 or C5)
no CE lite but car ran like crap
after lots of diagn, found that owner put some X Fire Plugs (4 electrodes) to get extra HP(ugh)
changed plugs out for Champion's
ran perfect

 

For clarity's sake, here are the recommended spark plug part numbers for both motors (from the owners manual):

Spark plug type:

2RZ−FE and 3RZ−FE engines
DENSO K16R−U11
NGK BKR5EYA−11

5VZ−FE engine
DENSO K16TR11
NGK BKR5EKB−11

Spark plug gap, mm (in.):
1.1(0.043)

If you don't have a paper copy of the owners manual, they can be found here: Toyota Manuals and Warranties | Toyota Owners for free.

 

I’m here to both Help and Learn!

I just learned.
thanks Andy01!