93runner223

ok took my 93 4runner to smog the other day

hc max 88 meas 80 at 15 mph
hc max 53 meas 53 at 25 mph

NO max 508 meas 557 at 15mph
NO max 761 meas 306 at 25mph

i cleaned the egr and put a new air filter

and also

there is a vacuum noise upon acceleration
like a little motor winding up

it gets louder with rpms
no leaks in engine bay
and sound can only be heard from inside

my power antenna is not hooked up somebody told me maybe the motor from it but idk

any help??

the_supernerd

I would guess that the smog and vacuum noise are related. There are a few ports on the throttle body that only get vacuum at certain throttle positions. Maybe one of those vacuum circuits has a leak, so you only hear it when you are driving it. If I remember correctly, most of them have to do with the EGR system, so that would explain why your NOx is so high.

I would have to look at a vacuum diagram to be sure, but I believe the egr system gets vacuum at partial throttle, then at higher throttle it gets vacuum from a different port that shuts it off. Hook a vacuum gauge to the hose that attaches to the EGR and rev the motor. The gauge should get vacuum as you rev it, but not at idle.

93runner223

ya basically the sound increases when at idle, iv already fixed most of the vaccum leaks such as pcv hose, brake booster and a couple others but its still there i just work everyday and u can really only hear it inside the cab not in the engine bay

the_supernerd

Is there a general location in the cab where it is coming from? There is a steering shaft grommet that is under the driver's side dash that wears out and lets noise into the cab, usually ticking noises, but other sounds could be possible. Also try listening under the vehicle for the sound. Sometimes noises in the exhaust are not heard under the hood, but can be heard in the cab and are noticable under the vehicle. Maybe you have an exhaust leak around the 02 sensor under the cab? That might sound like a small motor revving up that would be more noticable in the cab.