Noise at 1800-2100 RPMs

[Culpeper]

wonder if anyone with a 3.0L is having it? My 90 4Runner has 135,000 miles. Engine does not make noise in neutral, but only under load from 1800-2100 rpm, VERY noticable in the cab. It's a vibrating noise that appears to be coming from the dash. I don't think it is the speedometer cable and related parts because the noise is only RPM specific. The vehicle has an automatic transmission. Any ideas on what to look for?

[91 funrunner]

thumping,ticking,can you feel it in the seat or the whole car? need more details ;()

[Culpeper]

It sounds like a vibrating dash noise during that RPM range. Like something is loose and only vibrates within that RPM range. I can't feel it in the wheel, seats, or accelerator pedal. It's basically just a noise.

[Tomsriv]

That is a very common rpm range for V engines to resonate. Check your exhaust system mounts, transmission and motor mounts. If they are bad it might transfer more vibrations to the cab.

[Culpeper]

Okay, thanks! I'll check all that out.

[Culpeper]

Originally Posted by Tomsriv

That is a very common rpm range for V engines to resonate. Check your exhaust system mounts, transmission and motor mounts. If they are bad it might transfer more vibrations to the cab.

What about a "phrump phrump" while backing up in reverse. Sounds like normal V6 exhaust noise to me but someone told me it's a rod bearing. I had it at the dealership lately and asked them to diagnose the motor noise and they said they didn't hear anything mechanical noise. BTW, they couldn't trace down the buzzing noise coming from the dash. It sounds like a exhaust heat shield is vibrating and resonating through the dash.

[Culpeper]

Resolved the noise I was describing;

Using chassis ears pinned down the noise to the left fender well. Insulated/tightened down air filter box, mount point from fender to radiator, alternator wiring harness. The noise was harmonic meaning at a certain rpm range under load it would create a vibration through the left fender well. The noise/vibration would travel this area of the chassis like a bell and reverberate behind the instrument cluster inside the cab. So much so that to the naked ear you could swear the problem was with the dash or instrument cluster area.

[Tomsriv]

Thanks for telling us about the solution culpeper. To often people will not give any feedback on wether or not our opinions are useful. Could you tell the airbox was loose by wiggling it? Maybe next time someone has that problem I can tell them to check for missing bolts or mounts on the underhood parts.

[Culpeper]

Originally Posted by Tomsriv

Thanks for telling us about the solution culpeper. To often people will not give any feedback on wether or not our opinions are useful. Could you tell the airbox was loose by wiggling it? Maybe next time someone has that problem I can tell them to check for missing bolts or mounts on the underhood parts.

Thanks. No, the airbox appeared to be on tight.