Engine Vibration/Rumble After Mount Replacement

[get5007]

2002 Toyota Tacoma
2.4L
4 Cylinder
2WD

I purchased this truck roughly 2 years ago with 79,000 miles on it, single owner in Alabama (flat part of the state). It now has 137,000 miles on it.

Over the past several months there has been an increasing vibration in the engine. The roads I drive everyday are rough. The highways in Louisiana are **** and I work at a mine and have to drive roughly 4 miles of gravel/mud road everyday. I average 100 miles every day for my commute. I have recently replaced the fuel pump (shat the bed on me), rear shocks, front shocks (they were originals), and spark plugs. The vibrations continued to increase until the point were I decided to change the motor mounts and transmission mount.

The vibrations/rumble before the mount change were very noticeable in the steering wheel, front dash, hood. They were only noticeable when I am stopped (Park, Neutral, Drive). This was whether the engine was cold or warm.

After the mount change the car does not vibrate when I just start the truck up for the drive. As soon as the engine begins to warm up and I am stopped the engine will start to rumble/vibrate. I am now feeling the majority of the vibrations in the center console, seat underneath me, somewhat in the door. When I turn the A/C on the vibrations/rumble seems to smooth out. Again I can only feel the rumble/vibrations when I am stopped (Park, Neutral, Drive). My idle seems to fluctuate a little when idling. Every now and then it will jump up to 1100 and then back down to the 700-800 rpm idle. Also, I am hearing considerably more valve tapping than usual. It has been on my list to check the valve clearances but I have not had the time.

Any suggestions on where to start to chase the cause of this vibration down.

 

[WiskyT]

Rods or mains would be my first guess. If it is easy to drop the pan on that vehicle, pull a bearing cap or two and see how they look.

 

[toyotaslongtime]

I have a 1996 tacoma with the 2rzfe engine. It seemed like the engine had a little more vibration even when new. After about 120-140,000 miles the vibration got a lot worse. I checked all of the trouble shooting guides from cankshaft postion sensor, automatic transmission, drive shaft, harmonic balancer. No dice. A few days ago I found the problem. The radiator coolng fan clutch had no rear bearings, just the seal. When the seal popped out of position he viscous disc had nothing to keep it centered and it caused an imbalance. There can be many causes to engine vibration, but this was a first for me. The major question is even if the balls of the rear bearing fell out, what happened to the inner race?

update: I examined the cooling fan clutch again and after using a bright light can see both the inner and outer races. I wonder how many of these were borderline defective from the factory since mine vibrated a little more than usual even when new. I replaced the clutch fan with an electric cooling fan to see if I cam avoid this problem again.