dansouthwick

Hey guys.

1994 xtra cab p/u
3.0 motor
no lift
235/75r15 tires (less than 3k miles ago, still balanced.)
no extra mods (no lockers, ect...)
4x4

Truck ran great until last weekend, was driving on the road(nothing strenuous on the truck) and out of nowhere it starts vibrating between 2100 and 3000 rpm when i push on the gas regardless of trans gear (though the vibration gets worse the higher the gear i use) or speed. As soon as i go over 3k rpms or let off the gas all vibration stops. It also feels like the truck is alot slower tha n it used to be, lacking power. It also feels like its running at idle a little rougher. It holds the idle at the same rpm but it feels as if the truck is shaking a little more.

What I have done so far:

-Pulled rear driveshaft, checked for play in u joints, there was none

-With rear drive shaft off put it in 4HI, vibration still exists.

-Put it on a lift and checked all wheels for resistance/sticky brakes and bearing play (none exists)

-Checked front driveshaft for play and made sure when it's in 2wd that the front driveshaft isnt spinning.

-Cheked timing (its at around 10*, which is what the sticker on the inside of hood says is correct.)

-Checked all plug wires (nothing appears to be wrong with them and they are only about 6 months old)

-Looked around the engine bay, didnt see anything out of place, dont know a whole lot about the 3.0.


My guess is something in the motor is not working right. I assume ive already ruled out any driveline issues. Could it possibly be the cluth (it shifts smooth and takes off from a stop fine) Any ideas?

Thanks

Mike.Jax

Did you figure out what it was or does anyone have any thoughts on this? I'm having the exact same problem and was searching threads for a solution. I've got new spark plugs, wires, distributor cap, and rotor. I'm leaning towards the EGR Valve.

1995 4Runner 3VZE

Thanks, Mike

RJR

Sounds like it's misfiring under conditions of high cylinder pressures, which is what happens at low rpms and full throttle. Most likely cause is inadequate ignition voltage - the higher the cylinder pressure, the harder it is to fire the spark plug.

Could be bad ignition wires that arc over when the spark plugs require extra voltage (but you just changed those - are they good ones?), or a weak coil, bad distributor cap, or just need to change the plugs.

Less easy to diagnose would be a mixture problem at lower rpm's. VAFM not working properly, TPS flakey, ECT sensor bad, etc.

Mike.Jax

The plug wires were Bosch or the Auto Zone brand. I had to work on it on a Sunday and the dealers were closed so I couldn't get Toyota brand. Would it make that much of a difference to use these instead of the Toyota brand? The distributor cap, rotor, and spark plugs are new as well. I replaced all of these about 6 weeks ago and the problem started about 2 weeks ago.

At lower RPM's it seems fine. Also sitting in park and revving the motor to above 2K does not reproduce the problem. You have to be driving and have a load on the motor.

Just thinking out loud it couldn't be wheel balance or drive line could it? The trouble starts around 50mph and dissappears as soon as you let off the throttle, comes right back as soon as you give it throttle, so I was thinking that would rule out those two.

I appreciate the help. It's a strange one.

Mike

Mike.Jax

I phoned Toyota and the parts guys said he has seen this problem when you don't use their spark plug wires and recommended plugs. I ordered some and they are said to be arriving tomorrow. I'll let you all know the outcome.

Thanks, Mike

Gevo

The toyota parts guy is full of it. This isn't commonly caused by spark plug wire brand.

If it's an electrical issue, I think your TPS may be something you want to test. it could have a dead spot which gives the ECU some erroneous data and the spark starts not to match the actual cylinder positions. I just diagnosed a slightly different problem to be caused by the TPS. At throttling up from idle I was getting some popping, hesitation to increase RPM and a bit of a power loss. At the higher end of RPM range it was fine.

point is. check your TPS.

Mike.Jax

Turned out to be a bad U Joint. The vibration and sound got way louder yesterday and a popping sound began when running at low speeds. I took the drive line off this morning and hand tested the U Joints and the rear one was obviously bad. Put two new ones in today for good measure and it's all fixed.

The symptoms started as a mild vibration and noise. Oddly enough what I first noticed was the rear view mirror was vibrating making it difficult to see what's behind me around 60 mph. When you let off the accelerator the vibration and noise stops. Over time it got worse and began this behavior at around 30 mph then yesterday began making loud popping noises at low speed.

The U Joints I removed didn't have a grease gun valve and had obviously been changed out before. The only ones I could find today were the same kind. I'm not sure how long these last but it seems like the kind you can add grease to would be better. They are "Lifetime Warranty" but the $15 cost is nothing compared to the labor involved in changing them out.

We'll see how long they last. Thanks for the advice and posts. I hope this helps somebody who finds themselves in a similar situation.

Mike