I have a 98 4runner 3.4 auto 4wd. Just last week i noticed a hesitation under harder acceleration higher rpm's. the CEL is not on. Vehicle idles fine.. Also i noticed when this occurs at times i get a drive belt squeal noise?? Not sure if this is even related??? can a slipped drive belt cause this?? I know the basic things to look into but.just wanted some imput.. Thought about plugs/wires but wouldn't a mis-fire cause my CEL to come on?? Its driving me nuts. Thanks for any input.

 

a misfire SHOULD cause a cel, but a weak spark likely wouldnt. Start with the easy stuff, plugs/wires/fuel filter, and move on from there.

 

See heres the deal. My plugs and wires are only 20,000 miles old. I still know anything can happen. I just ordered my fuel filter and will have that in 2 days.. Is it possible though that a slipping drive belt would cause hesitation? I dont think it would but not 100% sure

 

Ok... doubt the plugs & wire then, unless you bought bosch or some cheap junk plugs/wires, which, I would then expect issues from day 1. Also... You did get duel electrode plugs... right?

Fuel filter absolutely could cause hesitation.
Drive belt? Unlikely, but anything is possible I suppose. Either way, I would fix the slipping belt a.s.a.p.

 

Yep dual electrode plugs from Toyota. lol i went just went to readjust the belts and the damn AC belt adjustment bolt broke! My damn luck

 

Take a close look at your sparkplug boots. They could have cracks in the bottom and cause a burn mark on the ceramic part of the plug

 

Clean your MAF sensor, it's quick and easy and if it's dirty might be screwing up your air to fuel ratio. Next try your front oxygen sensor. It had my 2000 running like a dog under a load. Hesitation, low on power and a little knock. The sensor didn't completely fail, although I did get a P0171 code (lean mixutre) on rare occasion.

The sensor is about $50 on rock auto and amazon.

 

I just changed my plugs after having several misfire codes, 0300, 0305, 0306 ect. they were > 0.01 from the new gap of about 0.031. that definitely cleared the misfire and rough idle. now I have a subtle stutter/hesitation when I start acceleration esp from a stop. I noticed a couple the old plugs had a "rusty" color right where the porcelain meets the collar. I thought be weird and maybe a crackd plug.
How would the cracked boot effect performance or create a misfire? wouldn't it have to be cracked pretty far up the boot? don't want to replacing boots.
I'll doing the other maint next, wires, maf clean etc