I have a '96 4Runner Ltd...... anyways I was driving around with the windows down, and pulled up to a stop light when I heard the engine making a slight knocking. I pulled into a parking lot to check it out... so when I popped the hood I could hear there was a slight knocking noise coming from the top rear portion of the engine. It sounds like the valves but it isn't the "regular ticking" noise... there is a suttle knock. I've search the forum, but didn't find much that relates to the 3.4 in this regard. My truck was due for and oil change so, I changed the oil, as well as adding lucas synthetic to see if that would remedy the problem, but to no avail. I'm thinking it may need plugs/wires, or maybe a valve adjustment, possible bad tank of gas? Has anyone else had this problem with the 3.4? This is the first time I've heard this noise, but the earliest appointment Toyota could give me is on thursday, so I want to take it easy on it. Any help would be great.. thanks.

 

How many miles?
When was the last time you had any work done to it and what was the work done?

 

190,000 kms ..... the last thing I did to it was change a faulty 02 sensor. Basically every other recomended service interval has been done... so the truck is upto date on everything. I should also mention that there is NO check engine light, NO power loss, NO abnormal symptoms, ohter than the slight knock itself.

 

Agent 7:
I had a similiar problem with my 96 3.4 last year (knocking at idle). Tightening the exhaust heat shields solved the problem. Try a search under "exhaust" and "shield", and see if any posts match your symptoms. If nothing else, its any easy and no-cost job. Good luck.

 

Thanks for the post... I'll definitely check that out....

 

I should mention though.... it sound like it's more of an internal problem, rather than something knocking on the outside....

 

I had a leeking exhaust header that sounded like a rod knock once. Check out the head around the manifolds. If you see carbon build up you have a leek.

 

Thanks, I'll check that in the morning....

 

i notice this knock too on my 00 sport. I dont know if its serious. But its a soft tone during idle. Idle around 700rpm with 112k miles on the clock currently. Either a slick knock or piston slap i dont know haha.

 

yup, that's the one I'm talking about.... it doesn't seem serious. I'm due for a tune up as well, so I'll see if that helps anything.

 

Well just to update... I changed the plugs and wires and air filter in the truck, and it eliminated the knock that was pissing me off. As it turned out, whoever did the plugs the last time didn't use the two prong plugs like they should have. In fact they used the least expensive bosch plugs which ended up getting fried. The wires on the drivers side showed signs of extreme heat, so I'm pretty sure the plugs probably weren't firing at they're peak. Anyways I'm happy it's back to the regular Toyota tick that I've become used to.

 

:pat:
This is one of those moments that I wish I had posted what I originally thought but didn't because I didn't want to sound too far off.

I had an issue like this with my Camry and a simple change of the plugs fixed is pretty easy. But since you had kept up with service I thought maybe that wasn't it.

Glad to hear you got it fixed though

 

Thanks man.

 

I changed my plugs today. Had about 10k miles on them seemed to cured it too.