Replacing spark plugs

It shouldn't be hard to find one. Pay attention to the torque range, lowest to highest, in the description of the tool. You want one where the low end of the range is something less than 15 foot pounds and the high end is something more.

For the mechanical click-type ones, it's also better to use a lower-ranged one (where 15 foot pounds is not near the bottom of its range) instead of a higher-ranged one (the tool can be less accurate when set in the extreme lower part of its range).

The simplest type, with a beam that points to numbers on a scale, is kind of foolproof, except that it's hard to use in positions where you can't be watching the needle and scale straight-on the whole time. That's really why the clicky or beepy kinds became more popular.

But first it might be worth thinking about various reasons, besides plugs, why your 197k car could be shaking while accelerating. (What is the car, by the way? Your profile says 2009, but you've posted here in the Gen 3 forum, for 2010 through 2015.)

 

IMHO; you should get a friend to help you out on the spark plug change and EGR clean-out. It's a "blind-stick" going into an aluminum head - really easy to cross-thread for someone that doesn't do this kind of work and doesn't have a "feel" for it. The best rule of thumb is, hand twist the spark plug all the way down and torque it down the last few turns. If you force it down with tools, there's a good chance you'll cross-thread it.

Just my two cents....

 

That's one among a bunch of things that can happen, though I'm not sure it's the first thing I'd think about with your symptoms. The valve can also stick open, which could give some roughness symptoms, but you'd be noticing those at idle.

A common contributor to rough running at mid-loads, like when you're accelerating but not aggressively, would be clogging of the EGR passages in the intake manifold. That would come kind of early in my list to check.

 

Make sure you avoid knock-off spark plugs from places like Amazon or eBay.

 

So did you clean it?

The spark plug torque spec is 15 ft/lb. While Toyota doesn't say, the lack of any mention of lube on the threads infers it's with clean/dry threads. The plug manufactuer (Denso) does caution to not use lube.

Anyway, for plugs I'd recommend either a 3/8" or 1/4" drive micrometer style torque wrench. Decent made-in-China ones can be had for about $30~40 USD. With the 1/4" drive torque wrenches be careful: they're typically incremented in inch/pounds. With them, if the torque was 15 ft/lbs, it's equal to 180 in/lb (15x12).

In the long run, a 1/4", 3/8" and 1/2" torque wrench are all good to have: 1/4" for really low values, 3/8" is a good compromise wrench, calibrated in ft/lbs, and 1/2" for higher torque values, wheel lug nuts for example.

You'll also need a 14mm or 9/16" spark plug socket, and at least a 6" extension. If your spark plug socket has an especially tenacious rubber insert (for gripping the plug), I'd recommend to wrap the juncture between the extension and socket with masking tape, to avoid possibly leaving the socket on the plug during install, which'll likely necessitate backing the plug out, starting again.

Do this with a cold engine.

Video #13 here is good to watch before diving in. Lot's of other very informative videos as well. Do note: he mentions to torque the plugs to 20 ft/lb, and slathers anti-seize on. Again, Toyota's Repair Manual says 15 ft/lb, presumably with clean, dry threads.

The plug is Denso SC16HR11 (the "16" was "20", but Toyota revised).