Long story short. Tried to get smogged and the guy didn't even start the test because of a port that is open on the I.M.

I checked different diagrams (even the one under the hood) and it looks like that it might be for the IAB check valve and solenoid but the valve and solenoid are no where to be seen.

I bought the car from a chick that was from washington state so I don't know if that has anything to do with it (different smog rules for different states). If someone from Washington can chime in and show me whats connected to their port that would be fantastic!

See video below for what port I'm talking about and what happens when I plug it with my finger.

Right before the lady sold me the car I asked her to smog it first and she failed. Since then I've changed the spark plugs, plug wires, distributor, air filter, cleaned the throttle body, and changed the map sensor.

 

have you considered putting a cap on it? if you cannot pass even with the cap you need the hose from there to solenoid on the IAB cannister and the hose to the flapper diaphragm thing. might have to go new or ebay for that.

 

or just run a vacuum line from the open port to the flapper diaphragm.

 

I did cap it off but I haven't had a chance to smog it yet. With the cap in I don't notice any driveability issues, but I do notice that when I put the car in neutral the rpms dip to like 400 then go back up to 700 or so.

I'll check on ebay tonight to see if I can find the valve and solenoid.

 

With the port open your getting quite the vacuum leak my friend. You should experience drive-ability problems with it open.

 

That's the thing. I'm getting no issues at all. I mean nothing major (and those have nothing to do with the engine)..

I've never owned a prelude before this one so I have nothing to compare it to but can't detect anything or I would have never bought the car. It is a huge leak and that's why I'm surprised I never noticed it until now (owned the car since the begging of august).

 

If I had to take a guess I'd say the idle set screw on the throttle body is mostly closed and the IACV isn't having to do a lot to keep the engine idling and it's getting enough air, but not too much, through the open vac port. I would cap it with a tight cap (or use a little gasket maker with it - ie Hondabond, etc), unplug the IACV, reset the ECU, and then see if you can get the car to turn over and idle. If not, adjust your idle set screw until it will idle on its own, then plug in the IACV and reset the ECU. From what I remember that is how you properly set your idle.

 

Thanks for the advice and I will try what you suggested sometime tomorrow.

Regarding the failed HC reading from the smog of the previous owner, will that leak in port cause higher HC #'s?

 

With a smooth idle it seems unlikely; timing and fuel trim will affect it though.

 

That port should have a vacuum hose on it and should go to your vacuum tank. It's part of the iab circuit. Your car will obviously have a vacuum leak with it disconnected. It's hose 12.

http://www.preludepower.com/forums/s...=271916&page=3

 

yes as it will alter the vacuum in the manifold and that is what the MAP sensor reads to get proper fuel and timing.

 

Nice. I'm thinking I'll be fine with smog then especially since that (HC) is the only thing that failed last time and I already replaced the MAP sensor with a new unit. I'll just keep the cap on there for now and not go to the same smog guy so he won't question why the cap is there.

The only thing that I haven't checked is ignition timing but that should be fine because the guy that I originally took it to for smog checked it then.

I'll reset the ECU when I get home from work, oh, and is the rule of thumb for resetting the ECU is 50 miles or 100 miles of driving before it "learns" your driving habits and its okay to take it to a smog place?

 

Regarding "driving habits", that's only for obd2 vehicles.

 

Yeah I kinda figured because I passed this time without driving a the 50-100 miles. The day before the smog I took the TB off and was adjusting the plate (kept getting a sticky pedal).

While that was off I looked behind the manifold and I saw the IAB check valve with the hoses and everything connected. So I connected the hose to the port in the manifold (the original one in the video) and went to the smog place.

Here are the results.

 

good deal, its always stressful for me when i fail a test. makes me glad my current honda does not have to pass emissions anymore!