Hello everyone,

I have a 98 4runner, 3.4, manual. I have a vibration only at 800-1100 rpm. It does it when its sitting still or rolling so that eliminates driveline issues. No CEL. I have replaced spark plugs, wires, swapped coil pack around, motor and tranny mounts, cleaned IAC and throttle body, checked for exhaust issues. Still there. I have an ultra gauge and everything looks good, fuel trims, O2 voltage, temps, etc. The one thing I noticed was that when at idle(no vibes) the timing advance is 14 degrees. When it starts shaking at 800rpm the timing changes to 10 degrees. As soon as it passes 1100 rpm the timing jumps to 20 degrees. Is this normal for the 5vzfe? Shouldnt the timing advance with the rpms? I have checked the harmonic balancer and replaced the clutch and no change. The timing advance is the only thing that relates to the vibration. This is making me insane, especially in the summer with ac on because it idles right in that sweet spot. AAAAAARG!! Any insights you all may have would be greatly appreciated. Thanks

hambob

 

Fuel injector?

 

hmm is it miss firing? it may be faulty injectors or a bad coil pack

 

if it was an injector i would think the fuel trims would have should it?!

 

I was thinking injectors too but the fuel trims are very reasonable. Short term fluctuates between -4 to 4 or so and the long term trim sits around 2-4 most of the time. MPG is 17-21. It feels like a miss but it runs great except in that 800-1100 rpm range. I unplugged the cam sensor today and it was worse, the cabin was buzzing. I don't know what means though. Thanks guys

 

bad knock sensors ? there are two and they die like any other
part...and the best thing is they are fairly cheap and easy to get to...

I would at least test them with the toyota specified test routine,
or just get 2 new ones and install them

 

Thanks for the suggestion. I checked out the knock sensor routine in the FSM but the first part requires i have thrown a code for one or the other sensor and the second requires a oscilloscope. I'm gonna try and borrow one from work in the next week or so and check the knock sensors, crank and cam sensors. Out of curiousity I unplugged the knock sensors and it made it worse but it didn't throw a code. Maybe its a 2 trip detection. I'm still puzzled. I was also thinking of pulling the timing belt covers to check its condition.

Thanks again