pplusent

1993 4runner 3.0 auto trans. Vehicle restored from ground up. Has been running great and still is, but when the truck is not quite up to temp it makes a sound occasionally when it goes to idle. At first I thought it was a broken belt, but after inspecting it the only thing I found was the tube at the air box from the egr system had blown off. Put it back on and the noise was still there. Problem is, when it makes the noise it only does it for about 15 second, so I can't get to the engine compartment fast enough to inspect it.
I am thinking it is coming from the air box because for the hose blowing off once and the hollow sound that accompanies the slapping belt sound.
I am thinking something in the egr system throwing exhaust momentarily into the intake system when it shouldn't.
Has any one come across anything like this? It's a sound I have never heard before in a vehicle.

Kolton5543

Are you talking about the the larger hose that runs under the intake? If so then its not part of the egr system. That is the frech air feed for the PAIR sytem. Its function is to pump fresh air into the exhaust causing the catalytic converter to burn hotter and be more efficient. Air is only supposed to flow into the exhaust. From what you describe it sounds like the pair valve might have failed and allows exhaust to flow back out that hose and blow it off and make the noise you describe. Also sounds like there could be excessive exhaust pressure. Get a hold of a back pressure gauge and screw it into the O2 sensor bung. While reving the engine it should have less than 1 psi of back pressure. anyhting more indicates a clogged converter or maybe a rats nest in the pipe. If the pair valve has failed then your best bet is to just delete it if your emissions testing allows it. If not you could probably find a used one cheap from somebody that did delete it.

pplusent

Yes, That is the hose I am talking about! Have never been sure what it was, just that it is mounted to the egr assembly. There is nothing indicating a clogged cat and the cat is only a year old, so it is probably the valve. It's amazing to me how dirty these engines are. I have a spare valve, so I will change it out in a month or so. I am installing headers and a new exhaust system along with a manual transmission and locker anyway. I am also considering new more efficient heads with performance cams that cleans up the burn and may not need the valve. This will also raise the HP above that of the 3.4.
Thanks for the input. It had me going at first. It was the strangest sound I had ever heard out of an engine.

Kolton5543

Make sure its the PAIR valve. Like I said before it is unrelated to EGR. As for if its needed or not. Its not except for emissions. As for a set of heads and cam making more power than a 3.4, you better post a dyno sheet. I have never heard of that and even if it is a thing, pics or it didn't happen.

pplusent

The head are dyno tested and the company that does the heads cuts there own custom cams and generally sell the complete engine fully machined and balanced with quality parts with a 7 year warranty for 2000 dollars plus shipping of 300. As far as I know they are the only ones that have performance cams for the 3.0. Hp and torque are at 3.4 levels, but come in at higher rpm than the 3.4.

pplusent

If you would like to check out the specs, go to: http://www.raptorengines.com/
I am a retired engine builder both automotive and aircraft and I build street and racing engines. This place literally put me out of business. For me to build the same engine would cost me over 4000 due to high machine work costs. I now just install these engines for the locals here. Their prices and quality are incredible!
These Toyota engines are a hard one to develop good HP being performance parts are non existent. Their engines are a great alternative too a 3.4 swap.

Kolton5543

Still wanna see a dyno sheet