strange vibrations (1 Viewer)

[64fabius]

I am the owner of a 1998 land cruiser 100 4.7 V8 with automatic transmission and while I was driving on the motorway I suddenly started to feel vibrations coming from the engine which decreased until they almost disappeared when I removed the D gear and went into N. I stopped and noticed that the vibrations were present even at idle but disappeared if I switched from D to N. With the TECHSTREAM diagnostic no error code appeared and about two years ago all 8 coils, 8 injectors and 8 spark plugs were replaced with original Denso spare parts. I went to a mechanic expert in automatic transmission but he ruled out that the vibration was caused by faults in the gearbox. In your opinion, could it be the engine mounts or gearbox mounts that are making the car vibrate? Or are the coils or spark plugs faulty again? Or are the valves starting to fail?
The problem of engine shaking and vibrations is more evident when I start the car cold. But after ten minutes, it seems to decrease even if it always remains present especially when the engine is under load at speed or uphill.
What do you think about it?
Thanks a lot for helping me.
Fabio
Italy

 

[elhombre]

Engine mounts are pretty easy to diagnose as a problem. Have a friend sit in the car and move the transmission from reverse to drive. You stand out of the way on the side of the car with the hood open, and watch the engine. IF the engine rocks back and forth excessively in the engine bay, then you can inspect the engine mounts much more closely to see if the rubber is worn out. You can also watch the radiator fan and see how close it is coming to the edges of the fan shroud as it rocks back and forth.

Bad coils should always set a code. To check for a burnt valve, you would need to do a compression test/ leak down test on each cylinder (when the engine is warm)

I would hope that the transmission mechanic was good enough to check out other possible problems too.

 

[64fabius]

Regarding the absence of DTCs on Techstream, I can tell you that although my car is currently without catalytic converters, because they were stolen a few months ago, no error has set after their absence. So in my opinion, the Techstream might not read certain error codes in a 1998 car.
I'll check the engine mounts as you've told me. Thanks