97HCivicEx

Alright so to star off the car is almost bone stock aside from a skunk2 alpha series 70mm throttle body. So when I first start the car cold it idles at 1,500rpms and I can rev it and it'll drop right back down to that, I have the idle screw closed all the way. I have check for vacuum leaks and haven't found a single one. After warming up it will fluctuate between 1,000rpms and 2,000rpms or it will sit at 2,500rpms at idle. I've replaced the MAP sensor and TPS sensor and it hasn't changed really at all. Ive been told it could be the IACV but can't pinpoint that to be exact I've tried tapping on it with the butt of a screw driver but it doesn't stop it from idling up and down. And I don't know where else to look. Any help would be appreciated so thanks in advance.

Former User

Post the year of your Civic EX and any CEL codes that are thrown.

97HCivicEx

No codes are coming up for it unless I pull a sensor connector for my map or TPS and I've replaced both of those. I have changed the air charge temp sensor but I don't know how to tell if that one is bad or not. It's a 97 civic Ex with a D16Y8

Former User

What was the logic of replacing those sensors if codes are thrown only when you unplug them?

Stop randomly replacing parts and start doing diagnostic tests.

Start by cleaning the IACV, and then adjust the idle speed properly. You don't want the idle adjust screw closed down all the way.

97HCivicEx

Because my TPS was my first though due to it sitting at 3,000rpms when driving down the road in neutral with my foot off the gas, and once I stopped it would idle down to 2,500. And I replaced the MAP sensor because when I had the engine off and key turned to the on position it would show a 2.5v which is what it should read for the throttle being halfway to wide open. I closed the idle screw to bring it down and I've tried adjusting it while it's running and it's not making any difference even with the screw almost all the way out.

Former User

This is not a diagnostic test for TPS function.

What wire did you test and what is the voltage reading now with a new MAP? A faulty MAP sensor does not cause idle problems.

Did you follow the service manual procedure for idle adjustment. If not, do so...and clean the IACV.

97HCivicEx

For the car at idle all of the sensors should read a .5v and with the car off the TPS ohm should be .666. I hooked it up to a scanner that could show the voltage and it was reading 2.5 so I knew the MAP was bad. I'll have to look up how to clean the IACV. And I'll get back to you.

Former User

I'm not trying to offend you, but this^ all sounds like your approach is to throw parts at the problem, as I stated earlier.

97HCivicEx

No I'm not offended I agree I prefer to fix stuff rather than throw parts at it. The only reason I did was because we hooked my car up to the scanner and the sensor was reading 2.5v with the key on and engine off so I figured it was a bad sensor since the TPS was adjusted to the idle position. And when we pulled the connector to the map sensor the car stayed running just fine and didn't throw a code when it should bog down and throw a code. So that's why I did those. I cleaned the IACV today and it idles a little bit better now it just roams between 1,000rpms and 1,500rpms so I think that could be the screw being closed all the way, just didn't have time to adjust before I had work. But I'm thinking about jumping up to a b series block at sometime so I'm just trying to get this thing to last me until I get one and finish the rebuild on that and prep it for a turbo haha 👍. But thanks for the advice it did help a little bit so I appreciate it lol

09chaplak

So what voltage is your TPS sensor reading with the plate closed again? Don't need the car turned over, just turn the key to the ON(II) position and take the reading.

97HCivicEx

With the throttle plate closed my TPS was reading 2.5v with the engine off. That's why I replaced it

09chaplak

Did you recalibrate the new one?

P.S. The TPS can be calibrated, so a new one might not have been needed. It pivots between those two screws so there is play.

97HCivicEx

Yeah I calibrated it to the stock .666 ohm when I put it on the throttle body

09chaplak

Calibrate it in volts, two different spots. .5 at with the plate closed and 4.5v at WOT.
https://honda-tech.com/tech-misc-15/...ensor-2169249/
Thread explaining it.

Do you still have your cruise control installed?

97HCivicEx

Yes the cruise control is still installed, I'll have to try that tomorrow and get back to you.

09chaplak

See if the hose connecting the cruise control module to the intake manifold popped off. Some overlook that area when checking for leaks.

97HCivicEx

I've already done hella vacuum leak test lol. Like 2 cans of starter fluid have made their way to my engine bay lol

Travlash

Check the iacv, take it out and clean it, also check the vacuum line running from the intake manifold to the cruise control.

97HCivicEx

I've already cleaned the IACV but I don't know where the cruise control hose is

Travlash

It's on the driver side above the wheel well it's circular and is black and silver . There is a hose line that runs to the back of the intake manifold

97HCivicEx

The hose is in good condition and connected right. And sealed. It only does it after its warm because when I first start it and don't touch the gas it sits at 1,300rpms

doson208

Haha wait. Your idle adjust is all the way in closing your plate and you don't think you have a vacuum leak? If you wanna keep throwing money at it just take it to a shop.

97HCivicEx

I've checked for vacuum leaks like crazy and yes my plate is closed all the way and I refuse to take any car I own to a shop lol

doson208

So if your throttle body plate is closed I wonder how the engine is running? How do you think air is getting to the engine? Through the flux capacitor? Gotta be a pretty substantial vacuum leak too. Most likely intake manifold gasket on the top side towards the middle of the manifold is where I see it most.

97HCivicEx

I haven't calibrated the flux capacitor so that could be it. Haha. No I think it's the IACV. Because I cleaned it and it was running good and idling at 1,000rpms. Then it started acting up again so I'm gonna have to get a new one. Or just ride it out for awhile until I get a new block