-1992 Honda civic vx hatchback, b18b1, p75 obd1, skunk2 throttle body, no FITV due to the throttle body. It is bypassed. Full exhaust no cat.

Problem: Once warm the car idles up and down from 1,000ish to 1,900ish rpms.

-History: When I first got the car it had a low idle once warmed. It was fine at star up. I think the problem started when I cleaned the iacv trying to get the idle to raise.

-Things I've tried to fix it that didn't change anything.
Cleaned the iacv again,
searched for vacuum leaks with brake cleaner,
cleaned the throttle body,
bled the coolant system just in case it had air.
new spark plugs, and valve cover gasket,
new thermostat.
tried different wires with no change.

-Things I've tried that has had some effect
Unplugged iacv - this causes the idle to lower and steady. This makes me think it is bad. Check engine light comes on which sets the car in factory limp mode??? So I'm not sure its the issue.
Plugged the hole in the throttle body that leads to the iacv. It significantly lowers the idle speed and almost causes the car to shut off.


Overall,
Is the iacv bad or how can I tell?
How do I test the tps?
should the car shut off completely if the iacv throttle body whole is plugged? If so that means I have a vacuum leak somewhere?
Ideas of what the issue could be?

 

Look up the idle adjust procedure in the service manual for the B18B1.

 

I don't know the B series much but all OBD1's should use a two wire IACV. When the valve is unplugged, a spring inside makes it close all the way and cut off the air through it. Thus the engine should slow down to less than normal idle speed. Your experience shows that your valve is working but when you plug the wires back in, the ECU is commanding it to open more than it should. The main reason for that is that the ECU is not getting a good reading from the ECT sensor and thinks the engine is cold (thus programmed to be fast-idling) when it is not.

If you unplug the IACV while running, the ECU immediately detects lack of electrical continuity and throws a code 14, lighting the CEL. This is normal. There should of course be no CEL and no codes with everything plugged in.

Blocking all the air bypasses in the throttle body should starve the engine for air and stall it out. This is good, it means there isn't a significant air leak. The stock setup has three air bypass routes: the IACV, an adjustable screw valve, and the FITV, which mechanically opens only when very cold.

 

Ronj, I knew I forgot something. I have done the base idle setting multiple times with no luck.

Mk378, From your post I take it that this mean the ect sensor could be bad?

 

Thoughts? When I plug the hole to the iacv the engines rpms do lower but don't shut off.
Mk378, From your post I take it that this mean the ect sensor could be bad?

 

With IACV unplugged, does it idle less than the normal of 750? You should be able to set up the intake so that is the case. Two wire IACVs should be set up so the engine slows down to almost stalling with the IACV unplugged and A/C etc, turned off.

The service manual tells how to test the ECT with an ohm meter.

 

Okay I will test it with a meter.
When I unplug the iacv it actually idles pretty decent. Almost a perfect idle really. That is with the idle adjustment screw all the way screwed in also. So maybe I have a vacuum leak? Ive tried searching with carb cleaner and have yet to find one

 

Describe how you did the procedure and what you observed.

 

Adjusting your idle speed (Gen3) - Team Integra Forums - Team Integra

It was done following this procedure above. I noticed symptoms listed about the idle surge. Setting the base idle doesn't changing anything. Sometimes a hanging idle will occur now also around 2,000 rpms. I noticed if I lift up on the gas pedal. OPPOSITE OF ACCELERATING the hanging idle will drop....

 

You need to make sure the throttle plate always closes completely when not pressing the gas pedal. The cable may be adjusted too tight, or something could be sticky.

Also check the TPS with a voltmeter to be sure it is returning to 0.4 volts at idle.

 

I will be checking these things tonight. The throttle cable has been adjusted so it should be good but I will check again. I will make sure its closing all the way though and check the TPS tonight. I have cleaned the throttle body before so hopefully nothing should be sticky in there. Is there any need to lubricate the throttle mechanism? I have a feeling a stock throttle body would fix some of these issues but the skunk2 is what I'm currently stuck with.

 

The question is whether you are able to set the base idle speed properly. Are you using an accurate external tachometer during the the procedure?

As mk stated, also verify that the throttle cable is not adjusted too tightly.

 

No I was doing it with the tachometer in the car. I do not have another one available. It has been almost a week since ive done this work. I should have some spare time tonight. I will attempt to set the base idle one more time, observe if I can set it to the proper rpms or not with the iacv unplugged. Check the cable adjustment and tps/ect sensor readings and report back.

 

^Inaccurate at low rpms.

Do the base idle set procedure while monitoring the engine rpms using an accurate external tachometer. Follow the B18B1 service manual procedure.

 

So here are some of the outcomes. Last night I adjusted the throttle cable and the junk2 I mean skunk2 throttle bottle to close properly. I also sprayed some lubrication on the return spring. The idle no longer sticks like before at 2,000 rpms. I blame this all on the aftermarket throttle body. The idle adjustment screw is pretty much all the way in.
What the car does now is if I am coming to a stop and just put it in neutral and coast to a stop it idles around 1k-1.5k rpms.
If while I'm coming to a stop I give the throttle a tap and let the rpms fall it will return to a perfect idle.

Overall I'm happy with it being much better but I will mess with it some more and try to get the throttle body to be more cooperative.

 

Away from traffic, do the thing where you stop and it idles high on purpose, then set the brake get under the hood and see if it will slow down if you manually pull the throttle plate shut.

If it is still something sticking, the cable itself could be sticky. It is not an expensive part.

 

So you're saying get out of the car and push throttle where the cable attaches? I still think its the throttle handing up. Maybe I can clean it some more. How will I know if the cable itself is sticking? If the cables sticking there will be tension on the cable correct? Holding the throttle slightly open?

 

Yes exactly. If the cable is taut it is something to do with the cable or pedal. If it is loose, the throttle body itself is sticking open.