Help...

1997 4Runner SR5, 3.4, auto, 4x4

Upon cold start the engine revs up to 1700 rpm and settles down to around 1400 and then finally down to 850. Well it has a nasty pulsing vibration around 1400 rpm. I can feel it in my seat, floorboards, and slightly in the steering wheel. If you open a front door and lay your hand on the outer edge you can feel it and even see it.

Put it in gear and it's gone. Put it in gear, hold the brake, and raise the idle to 1400 rpm and its gone. Its only noticeable when in neutral or in park and around 1400 rpm. Its driving me insane. I pried on the tranny mount and it made no difference. I've only owned it for 6 months and it has done it since day one.

Any armchair diagnosis? T-Belt off a tooth? Thermoclutch on the fan? Ignition? It does have factory wires . I drove a 99 today and it felt like it had noticeably more power. My wife drove it and she commented the same thing.

Any TSB's or patterns I should look into?

Thanks gang!

Jim

 

I'm wondering if the flywheel could be off balance slightly? Since it only happens at that particular rpm, it would seem like it's something resonating. Try revving it to a higher rpm, try 2800, and see if it does it anywhere else.

 

Above 1800 rpm and I can't detect it. Less than 1000 rpm and I can't detect it. I'm hoping it's been like that since 1997 and I'm just being 'sensitive'.