Lharris_95

I'm new to the forum and I've looked all over the Internet for an answer but have yet to find one. I have a 95 4Runner 3.0 that I bought a couple of months ago that has had the same "unfixable" problem ever since. The check engine light is showing the knock sensor code but the weird part is the light is off when I first start it up and it drives great! But after a couple of miles the light comes back on and it starts to run terrible like its in limp mode. I've taken it to 2 mechanics who have replaced both of the knock sensors with oem sensors and that didn't work and then with factory Toyota sensors and that didn't work either. I really want this thing running good or I'm gonna have to sell it. Does anybody have any clue what it might be. We have also tries changing the PCM and that wasn't it either. I need help!!

BamaYota1

You need to run a new wire from the ecu directly to the knock sensor. The wire needs to be a shielded wire. Either a coaxial with the thin wire grounded to the ecu body or a thick silicone wire like GTO. On the 3.0, there is also a pigtail under the intake that is known to go bad that you should replace. I hope your mechanics would have changed this pigtail as a precaution. There are tons of threads on this if you search.

BamaYota1

Btw, it is normal for the knock sensor code to only come on after a mile or so of driving.

Lharris_95

They did replace all the wires so I assume the replaced the pigtail too. But it's still lagging and the rpms aren't very steady. It has a lot of trouble just getting over small hills that it shouldnt have a problem with. If its showing the knock sensor light and we have replaced them and the wires then why hasn't the light gone off and why did that not fix it?

BamaYota1

Because it has to be a shielded wire. A regular wire will not work, as it lets noise into the line and trips the ecu. Lots of guys will run coax and ground the outer wire to the ecu. I prefer using GTO wire which is the wire used in neon signs.

Your truck goes into limp mode when the knock sensor code is triggered.

Other than this, I don't know why your mechanic let you have a vehicle back when he didn't fix the problem. You should really ask him. Otherwise, perhaps you should just fix it yourself. All the info and help you need is right here on this forum.