Didn't see your posts around Christmas as I was out of town. When you unplugged that line that stopped the surge, did you plug the port to the intake manifold?

That line looks like it goes to the MAP sensor, but has a T before the MAP sensor. If you follow that line, it should just end and have a plug to stop a vacuum leak.

The 91 accord should have a sticker under the hood showing the vacuum line routing. It could be long gone by now. The original vacuum hoses on the accord are also numbered, so it can help you figure out the vacuum hoses as a reference.

 

Yeah, that goes to the MAP. Plugging the hole on the manifold brings idle down but makes the car run rough.

Also, a new bit of info - when I hit the throttle and gradually bring it down, up until my foot is all the way off the pedal, the car hovers at 2000 RPM. I think i may just have a high idle that the ECU is trying to cope with via the IACV. I have no idea though.

 

I never finished my diagnosis of the TPS either. I can mess with that too but I was just confused on what those readings should be.

 

OK, TPS is now calibrated and working properly. Update, on inspection,the idle screw has been dickered.... let me mess with it a bit.

 

While driving, idle is also very high causing hard shifting and the car wanting to travel sort of fast while foot off the throttle. Idle screw is cleaned and put back in all the way. What could possibly cause the computer to tell the IACV to constantly draw in a bunch of air? some other sensor?

 

The idle screw is a set screw I believe for stopping the throttle plate, so it can be adjusted. Get the car to operating temperature and adjust that screw so the car idles around 700 rpm. Look closely at the tachometer, because the first mark will be 500 rpm and not 250.

Follow that vacuum hose that you plugged at the throttle body. The hose branches to the map sensor and also continues. That hose should end and have a plastic plug to prevent a vacuum leak. This could cause a faulty map reading and is easy enough to check.

 

Sorry, I forgot to mention but that branched hose goes to the "vacuum box" near the battery. when i close that hose nothing changes. I can experiment more, though. I have never seen the car idle under 1000, it seems that it wants to be at 2000 even with the screw all the way bottomed out - as far in as it will go.

 

Do you think I should take off the throttle body and thoroughly inspect/clean it? There was a little bit of carbon when I just reached in and cleaned it.

 

I looked at hondapartsnow.com to find which hose you were referencing, as I thought you were referencing the map sensor. I could have looked up the wrong part.

I thought the idle screw is opposite of how you are describing. If you loosen the screw, the depth is less, so the throttle plate can close more. I can definitely be wrong about this, because you should never need to adjust that screw. Idle problems are usually caused by some other issue.

 

Yeah, that hose in the diagram i posted tee's to the map sensor and the other end of the tee goes to the vacuum box.