96 tacoma, 3.4 litre, 4x4, 5 speed with 173,000 miles. Here is my dilemma. My front o2 sensor started to fail (error code was thrown) and after ignoring it for some time it started to affect my performance (real bad hesitation during acceleration) and I replaced it. At the same time I did some basic maintenance plugs, wires, fuel filter, clean and oiled my KN air filter, cleaned the MAF, ran fuel system cleaner and injector cleaner through the system. After doing all of this my performance was improved but I had the same hesitation that I had before replacing the front o2 sensor, just not as bad. So I had the cat pressure tested and it was clogged and as stated in a previous post I was going to run straight pipe because a new cat was $748.00, as it turned out it was cheaper to get an after market high flow cat ($108.00 installed) than to get a custom pipe made and installed and if for some reason I ever wanted to pass emmissions I could and no need to buy and install an o2 simulator. The hesitation I refer to only happens during full throttle (at 3/4 throttle the engine runs like a dream) and it seems to only occur in 2nd and 3rd gears. Anyone have any suggestions as to what I can do next? I did pull the plugs and examine them, they looked just fine and I ohmed out the coils and they were within specs. My thoughts were fuel rail, injectors or fuel pump, these problems are a little bit above my abilities. A shop will probably charge quite a bit to diagnose and fix this problem. If anyone had a suggestion as to what I could do it would save me much money. Thanx to all!

Clean your thottle body out. It get a mess of gunk in it.

Also run you some SeaFoam though the PCV line to the thottle body side.

Reclean the MAF. K&N filters cause more problems than they're worth.

ttus,
I appreciate your feedback, how do you clean the throttle body and with what?

What do you mean they cause more problems?

Here ya go It's for a 3.0 engine, but the idea is the same; don't overuse your product tho', use just enough to get the job done; t'body needs cleaning, not a deluge. <img src="/forums/images/graemlins/kewl.gif" alt="" />

K&N's may be okay for more air, but they also let in more dirt. Also, if they're not serviced properly, they'll gum things up for you. This is quite a common problem actually.

This is the other item you need to clean up; took me a bit to find it; it's in the 30K maintenance article

MAF cleaning