Idle Fluctuation after Intake Removal

[Answeraccording]

1999 2.3L 5-speed sedan, custom blue pearl
1999 2.3L 5-speed sedan, purple raisin (parts car)
2000 2.3L Auto, sedan, black (borrowed from friend until i sort this out)

One day I was on the highway in 5th gear, when I pushed the accelerator to the floor there was nothing but hesitation and stumble. I was only able to maintain speed or accelerate by feathering on the gas pedal. I barely got the car home and it sat for 30 minutes before I tried to move it again. At this time there was no issue and I was able to rev it smoothly all the way up. Ordinarily, I would wait for an intermittent issue to repeat itself before jumping in to it, but it was the Friday before the Eclipse and I was supposed to be driving 9 hours to Kentucky. I knew from this point that there was nothing I could scientifically do to prove that I had fixed the car to take it on a road trip. But, I figured I should check some stuff out. I saw that the EGR passage could be a problem, so I removed the intake plenum. The passageway was completely plugged which led me to believe that it didn’t happen the day before, but has been a problem for a while. No code has ever shown up for the EGR. I separated the throttle body from the intake and cleaned them. I also removed the IAC from the throttle body and cleaned it. I installed everything with new gaskets.

Since I got it put back together it has been running poorly in a different way and this is what I am hoping you can help me with:
When I start it, it revs high. Around 2000 rpm. If left to its own devices, it will gain to about 2200 rpm after about a minute and then step up again to 2500. If you touch the gas, it immediately drops and starts fluctuating between 1500 and 2000 but it will start on ts own after about 3 mins No codes are thrown.

I have tried disconnecting the IAC and pulling the #13 fuse on the right side dash panel to reset the ECU in hopes of lowering the idle.

I have been going through the Eric The Car Guy "speech" on Honda hunting idle issues: I have bled the cooling system, and used propane to check for vacuum leaks - this was inconclusive but it was very hard to tell if the propane was affecting it with the idle raising itself and then starting to fluctuate. I cannot rule this out so I will try again today and update.

Other information about the car that could be pertinent:
My catalytic converter was broken internally from an accident last fall and has been displaying code P0420 since then, but always running smoothly. i replaced it a few days ago and there is no change in the condition described above. code P0420 was succesfully erased and has not reappeared.
I have also replaced spark plugs to eliminate them from fault, and the air filter because it was nasty.

any thoughts or suggestions would be appreciated.I don't think I'm even back to where i was before i took the intake apart and I really need to give my friend's car back. I'm running low on ideas. Thanks in advance.

 

[dawg316]

sounds like an intake leak for shure. smoke test the intake.

did you clean your gasket surfaces super clean before you used a new gasket?

edit*

also withe the car running. and the intake snorkel off. you will see 2 holes inside the throtal body. plug 1 and see if the idle changes. if not plug the other hole ( just put your finger over it) and see if the idle changes

 

[Answeraccording]

dawg316 thank you for your reply. i did clean the gasket surfaces very well, and reinstalled to proper torque. i don't have smoke machine available ATM. do you think this is something i could pick up with propane if aimed correctly? or is the smoke more precise? i took off snorkel and i can only see one oval shaped
hole on my side of throttle plate positioned at about 10 O'Clock, when i put my finger over it the car dies immediately...major air moving through here. is this an IAC port?

 

[dawg316]

havnt done it on an accord but one should be the IAC port. and the other for the FITCV port. il check my spare engine and see what the ports go to.

ive never used propane. always used an airesol can ( brake cleaner carb cleaneer ect) to spray at some spots to see where the air leak is coming from. spray all the vac hoses to see if some have developed a crack. but what i have seen is spray the flanges of where the upper intake bolts to the lower, and were the IACV bolts to the intake. you may find a leak there.

spray your aeresol at the suspected leak and listen for a idle change.

whats kinda odd with your situation is when you covered the IAC port the car died. its almost as the IACV is keeping your car idle alive. so i would be leaning more to an air leak than a mechanic/sensor fault.

 

[Answeraccording]

Thanks again for the quick response. I'm curious what result would you expect from a healthy engine when covering that IAC port? I'm going to head down to the garage and will update after aerosol test.

 

[Answeraccording]

Wow.. That was strange. Flammable liquids in aerosol cans seem to have no effect on this running engine. I grabbed some carb & choke cleaner and started spraying around a bit, I've never seen a clear example of this test working so I wanted to see what it would sound like when it did hit the engine. I pulled off the snorkel again and gave a little squirt... nothing... just surging and dropping like always. I ran back upstairs and checked the computer in case you didn't say Carb Cleaner, and saw brake cleaner too, I tried that in case my Carb cleaner wasn't flammable enough then closed up the snorkel and started pulling off other vacuum hoses and spraying around. Nothing. I even took a shot with starting fluid thinking I might blow up. Nothing to report. I couldn't find a place to spray anything that made any discernible change. I was always lead to believe that spraying stuff into a running engine made it rev higher, and it sure seems logical. What gives? is it so rich that it cant be richer?

 

[dawg316]

i use carb cleaner myself and it works. kinda confused on how your cars acting. is it constantly surging. no matter what condition?

 

[Answeraccording]

Yes. When the idle drops a few minutes after a cold start it goes between 1000 and 1500 RPM and there is nothing I could do with flammable sprays to alter that condition in the engine. I found it completely baffling, it seems to defy all logic. I think I will make a video so people can see.

 

[dawg316]

what happens when you unplug the IACV , do you notice an idle drop ?

you cleaned the screen on the IACV when you removed it. did you add a little RTV to the o-rings on where the IACV meets the manifold?

also you cleaned the EGR passages. you for shure used a new upper intake manifold gasket. and also a new Throtal body gasket?

the problems started occuring when you removed the upper intake to clean the EGR. retrace your steps from when you removed the intake. and double check every vac house and connector.

Kinda stupid question but the MAP and TPS sensor ( located right next to each other ) on the throtal body can be interchanged by accident. make shure you dont have them in the reverse order

 

[Rusty Accord]

what happens when you unplug the IACV , do you notice an idle drop ?

you cleaned the screen on the IACV when you removed it. did you add a little RTV to the o-rings on where the IACV meets the manifold?

also you cleaned the EGR passages. you for shure used a new upper intake manifold gasket. and also a new Throtal body gasket?

the problems started occuring when you removed the upper intake to clean the EGR. retrace your steps from when you removed the intake. and double check every vac house and connector.

Kinda stupid question but the MAP and TPS sensor ( located right next to each other ) on the throtal body can be interchanged by accident. make shure you dont have them in the reverse order

X2. Go over everything. What you might find is a pinched "O" ring. I only say that, as when I did the same job on my wife's car (upper intake manifold removal to clean the EGR port), the IAD multi stage "o" ring got pinched after I replaced the valve (idle kept bouncing between 1500 and 2,000 rpms). Since the "O" ring was now shot, I filled the groove in the IAD with high temp RTV, and topped up the coolant level. I then let it learn where it was supposed to be per the FSM. No issues with the idle speed in the last 18 months.