SOHC_civic_si

Hey guys, I really need some help here.

I cleaned the IACV on my D16Y7 and when I started it up after I put everything back together, the idle climbed all the way to 3000 RPMs dropped down to 2600 RPMs and then back up to 3000 again. It just continues to do this.

I think I know what the problem may be but I need input. When I took the throttle body off, I removed the TB gasket to wipe it because it had coolant on it. Anyways, as I was carefully wiping it, the gasket bent a little. I panicked, but it seemed to straighten back out fine. Do you think there is now a vacuum leak or something?

Thanks for the help.

djslim23

It's likely, I had a vacuum leak and my D acted the same exact way. I'd at least start with a new gasket since they're dirt cheap and it's a good idea to replace it if it's bent, even if it's not the source of the surge.

Former User

Does blocking the IACV port inside the throttle body eliminate the surging idle or have no effect on it?

Any CEL codes?

If you removed the IACV coolant hoses, did you bleed the cooling system?

SOHC_civic_si

I haven't checked for any CEL codes (light is always on because there is no catalytic convertor- have to use a code reader to check), and have not yet tried blocking the IACV plate.

I did remove the coolant hoses but did not bleed the system. Is this something I should have done?

Former User

You can pull the CEL codes using a jumper wire. Click the CEL sticky at the top of this subforum.

Whenever you potentially introduce air into the cooling system, you need to bleed it.

SOHC_civic_si

Blocking the IACV port kills the engine, but if I block the plate and then open the throttle plate a little manually, the engine runs fine. This couldn't be an issue with the cooling system or TB gasket now could it? Because the engine would still surge even if I blocked the plate and raised the idle myself?

Is it possible I ruined something when cleaning the IACV? I pulled it out, and just sprayed the crap out of it with brake clean then let it dry for 25 minutes?

Former User

Pull the CEL codes. Then reset the ECU to see which CEL codes repeat after running the engine. Post codes that repeat.

Also make sure the throttle cable has about 1/2" of slack. If the cable is too tight, it will hold the throttle plate open and thereby cause a high idle.

SOHC_civic_si

No CEL codes (other than the catalytic converter one that is always on). Throttle cable is also fine.

I was reading that you should replace the IACV gasket when cleaning..other than that, I'm stumped. When I block the IACV port, and work the throttle manually, it runs fine. It has to be the IACV? But wouldn't it set of a CEL, or could it be that gasket?

Former User

Bleeding may take 20-30 minutes:

1) Park the car on an inclined driveway with the front end higher than the rear.

2) Push the dash heater lever/**** to MAX heat.

3) Follow the directions in the diagram below

SOHC_civic_si

I'm going to bleed the system tonight. I'm just wondering if it's dangerous for my engine to run it that long when the idle is surging from 2600-3000 RPMs.

Former User

Based on your information, the high idle is caused by the IACV opening and allowing too much air to bypass to the intake manifold. This could have multiple possible causes, including trapped air in the cooling system that causes the ECT sensor to falsely read a cold temperature or more likely a stuck open IACV (mechanical problem).

Prior to bleeding the cooling system as I suggested, check whether unplugging the IACV connector causes the idle speed to drop. Post the results as this should help to pinpoint the problem.

SOHC_civic_si

Unplugging the IACV connector causes the idle to drop to 1500 and almost misfire or surge quickly between 1500-1600. CEL came on after doing this.

Edit: finished bleeding the cooling system, and the idle still surges. Only this time it surges from operating temperature (~700) to ~2600 RPMs.

Now I don't even know if it is the IACV, because the idle drops when it is at operating temperature, but still surges back up? What the heck is the problem here?

I'm getting so frustrated that I'm on the verge of taking it to a shop.

Former User

1) Does unplugging the 2-wire ECT sensor under the distributor cause the idle to settle down?

2) Do the same test on the 3-wire TPS attached to the throttle body.

SOHC_civic_si

1) Does nothing and the surging does not change.

2) Idle holds steady at 4000 RPMs

Former User

Do you have a multimeter?

Former User

Since bleeding the cooling system, what happens to the idle speed if you unplug the IACV connector or cover the the IACV port with your finger?

Do you have a stock D16Y7 engine? What year?

SOHC_civic_si

So just as a little update if anyone has a similar problem, I replaced the IACV and the problem was solved.