All of a sudden, my Montero started a strange vibration. It occurs randomly for a few seconds, then stops when I let off the gas. The best way to describe it is it's like I drive over the wake up strips along the interstate. Then my ABS Brake light came on and has not gone off. I regularly drive 200 miles to Michigan. I'm a disabled vet and can't afford the $70 at the shop JUST to diagnose and then whatever repairs. Would appreciate anyone's input. Also, it doesn't seem to happen at high speeds, although it could and I just not notice bc all of the road construction on the interstate is horrendous. lol

 

Its possible that hydraulic brake booster accumulator had failed. That would produce the rumble strip type of a sound, especially when you press brake pedal. The ABS light being ON would point in that direction too. I believe that booster motor would cycle by itself while driving trying to maintain the pressure and that accounts for the sound without pressing the brake pedal.

 

My 2003 had a vibration and clacking/tapping at certain speeds like you describe. It was obviously motor related because I could just tell it wasn't suspension or wheels. It was the butterflies in the upper intake plenum. On mine they were installed with screws...really dumb-butt feature. They should be welded or one piece. Tiny screws started coming out and the little half-moon shaped plates began rattling at certain times. As soon as I let off gas it would stop pretty quick and then start again randomly on throttle. My motor ingested one of the small screws and I guess blew it into the catalytic converter. I never found it.

The fix is to remove the butterflies completely. Very easy. Remove plenum and turn upside down...there they are.

I've noticed no difference in any performance. One guy said at cold temps and low RPMs he kinda felt a rough idle but that was oversees in desert. I live in cold Colorado at 6,500 feet elevation and have not noticed anything.

 

Is this on a Montero Sport models? I am not familiar with the butterflies in the intake plenum (full size Montero), but I recall reading something like that before.

 

Mine is full size 2003 3.8L 6G75. Not sure if on other models or not.

 

Got it. It must be a 3.8L design feature. Mine is a 3.5 and has different intake manifold without the internal valves.