Hi all,

When in 3rd to 5th gear at 2-3000k rpm my 98 3.4L 4Runner with 120k miles studders during acceleration, not while idling or cruising speeds. I've installed a new fuel filter, air filter, and throttle position sensor (TPS) without improvement. The spark plugs were done about two years ago and the auto shop said there are no error codes on testing.

What should I do next?
Thanks for your help!

We'll need to know what year and engine your 4Runner is to be any help

It's a 1998 four-wheel drive 3.4L

98 3.4L 4wd

I had a similar problem that ended up being a faulty coil pack. It would run better when I first started up and would get worse the longer I drove. Under load the engine would misfire/stutter more. All three coil packs tested within toyota specifications, but one of them had a lower resistance value than the other 2 and once it got hot enough it wouldn't spark strong enough.

If that were the case wouldn't I have a misfire code (which I don't)?

Mine did that too, was also a bad coil pack and it took forever to throw a code. I think it did it for 6 months before a code popped up

Same scenario but mine ended up being an injector.

I had the same issue but mine turned out to be the boot on a spark plug wire allowing the spark to leak to the head. At first it was only under serious load but it eventually became an issue at almost any speed. Found out exactly what it was one day when it was humid out and could actually hear and see it arcing at idle. Also didn't throw any codes until just before I was able to diagnose it.

Same for me and the 97 Puppy Hauler. One of the coil boots had a hole burned through it from the spark under load.


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Troubleshooting ignition problems can be annoying. I think codes are not thrown until a misfire occurs a certain number of times within a specified time frame (I might be totally wrong here)

I'd pull check plugs even though they were replaced not too long ago. They could be indicating another problem you have leading to this issue. Just make sure none of them are fouled up.

Check coils and compare resistance. As others have said, one may not be providing the umph needed for good spark anymore.

Check your ignition wiring.

A nice little upgrade for these old trucks would be to just go ahead and replace all plugs, coils, and ignition cables with new. I used NGK plugs, OEM coils, and NGK wires. The engine ran noticeable better after that. Good luck!

It took 2 months before it finally set a misfire code. I ended up downloading a bootleg version of toyota techstream on a crappy laptop I had to look at live data.

Well, I went ahead and replaced all three coil packs and six spark plugs. The old plugs looked like they had regular wear. It didn’t shake for about a week but started again yesterday; apparently that wasn’t the problem. Any further guidance?

Ohm out the injectors 13ohms at 20*c 16* if hotter.

No idea what that means but I’ll try to find some video on it. Thanks!