dog2525

Hey guys, I have the weirdest problem I have ever seen on civic. A little brief history on the car. Got it as a theft recover with a missing head. Slapped on a pr3 head I had from my previous car with a obdI style intake manifold. It drives and shifts good, but it idles at 1500 rpm no matter want, and it fluctuates from 1k to 2k especially when coming out of gear. I have cleaned the fast idle thermo valve, and idle control valve numerous times and it still persists. I have even replaced the throttle body and idle control valve and still no go.

Here's a sample of whats happening.
http://s153.photobucket.com/albums/s...t=MVI_2441.flv

Engine Bay:

Former User

Any vacuum hose disconnected from the IM? Is the IM torqued to spec with a new gasket? Have you bled the cooling system? What are the CEL codes?

dog2525

All vacuum hoses are connected, even to the charcoal box. The intake manifold is torqued down to specs with a new gasket. (I don't there is a vacuum leak, but you never know.) The cooling system was bled, (ran without the cap in till the fan kicked in.) The car has been sitting for a while and only today I took it for a test drive and so far the CEL didn't kick in. It did through a code awhile ago, but I forgot it.

Former User

When the engine is warm, pull off the intake and cover the port leading to the FITV inside the throttle body with your finger. Does this lower the idle speed and stop the surging? Do the same test on the port leading to the IACV.

EKJOE

My initial thought was vacuum leak, But then I remembered when I was having this problem with my LS/V and I found the problem in the engine harness.

My idle surge was more erratic than your's but doing continuity check from the ECU side of the harness to the IACV plug in the engine bay would definitely not hurt to rule out wiring as the issue. You can find the pin out diagram for your vehicled harness all over this site and Google.

But I think first and fore most like Ron said, Figure out what CEL codes your throwing and then post em up. That will at least get you out of the guessing game and onto to finding the real problem.

dog2525

Just came from 20 min or so test drive and sadly the CEL didn't come on yet. As far as the test goes, with the car warmed up, covering the lower hole which I think is the FITV had no impact on the idle. Covering the upper hole on the other hand dropped the idle down where its supposed to be at around 700rpm. So what does that mean?

Former User

Does the CEL work? If there are no codes, the CEL should turn on and then off after 2 seconds when the key is turned to ON(II).

Sounds like an IACV problem. What happens to the idle speed if you unplug the IACV connector? Have you tried adjusting the idles speed to spec with the idle screw on the throttle body? Have you tested the ECT and TPS sensors?

dog2525

Yes, the CEL does work, it just the sensor didn't tip it off yet. Yes I did adjust the idle through the screw on the throttle body, but it didn't help with anything. I am going to see what unplugging the IACV does. Also how would I test the tps and ect sensors? see if there is voltage going through the wires?

Update: Disconnecting the IACV caused only caused the CEL to come on, no idle changes. Plugging it back in though, caused the idle to fluctuate between 1600 and 1700.

Former User

dog2525

Ok done checking and got .3 ohms on the ECT with the engine hot and off. I couldn't get any readings of the TPS. Tired with the ignition on, and pin 1 and 3 on the tps. couldn't get any voltage to show. ac and dc. Also found the autozone printout of the CEL. It was code P0505.

jaydeem2002

i had the same problem a while ago and it turned out to be the idol air control on the back of the intake maini.

Former User

If you mean 0.3k Ohms (=300 Ohms), then the ECT is fine.

With the TPS plugged in and the key in ON(II), measure voltage between pins 1 and 2 (Grn/Blk and Red/Blk wires) in the TPS connector.

JDM_Ek_tuRbo

IAC sensor bro. happen to my old hatch and my boys and i just bought a new sensor and worked fine.

dog2525

Ok, the TPS is as follows: .28 closed and 4.28 with full throttle.
Going back to the coolant question. I was wondering if having a t stlye hose to distribute the coolant to the FITV, IACV and throttle body could be problem. I attached a image of how the t hose looks like.

Former User

TPS seems okay.

Is the ECT resistance really 0.3 Ohms with the engine fully warmed up?

Former User

A bad IACV is also possible, as mentioned.

JDM_Ek_tuRbo

its going to be the IACV, cuz the way he explains it...i had the same problem with my hatch and i remember putting a cig butt for a week straight just to keep the idle right. ghetto but don't try it haha just replace it kid. thats why i had my share's with honda's and went to something else lol

dog2525

I am in the process of stealing the IACV from my brothers integra. going to swap it over and check it out. And Ron, I think it was .3k ohms. I'll double check that.

JDM_Ek_tuRbo

ohh alrighhtt. steal your bro's sh**!! hahaha wow no comment.

dog2525

My brother is cool. Well it turns out the bolt pattern is different on his IACV. Anyone know how much one costs?

JDM_Ek_tuRbo

yea i knew it wouldn't work cuz your bro's a teggy...a new one is mostly like $165 bucks at autozone. if you buy a used one later down the road it'll do it all over again. might aswell just spend the money and be happy

Former User

The coolant hoses to the IACV only serve to prevent it from freezing. That's not your problem.

In contrast, coolant hoses to the FITV are important for it to work correctly, though the FITV does not seem to be the problem.

Tico Loco

Hi, I am from Costa Rica.
Double check your idle control valve becuase is a very common problem in some honda engines. You may have cleaned the idle control valve, but are you sure is working? With a damage idle control valve the ecu do not show any codes in most Honda. If you have any other damage sensor or a vaccum leak the idle is not steady. If you have a steady but high idle be sure the idle control valve is okay.
I know you have a Si, but this is a very common problem in the 1997-2000 DX and Lx Civics.
The Tps do not do much in this model, it is like a reference to the ecu. Almost everything is base on the Map sensor and Crank sensor, its a Motronic base fuel inyection, not a J-tronic. In old model cars ( European and Japanese ) Tps rules almost everything.

Problems like vaccum leaks, Map, rich mix, stuck open fuel inyectior, fuel pressure regulator to not increase idle that much. How is fuel consumption?

Check the throat body for vaccum leaks at the leverage, I have seen some similar problems with a very old or modify throat body ( overbore )

Also check the gas cable free play

JDM_Ek_tuRbo

^^^ this guy!! hahaha read it bro. he's buying a new IACV sensor.

dog2525

Update:
Alright guys, I stole another IACV from a buddy who's rebuilding his engine, and after slapping that thing on, and adjusting the idle via the screw on the throttle body, what can i say, IT WORKS!! It idles smoothly at 750 or so rpms. I still need to go buy one myself, and take it on the road for a test drive. As I said in my first post, I swapped over another throttle body and IACV and the problem persisted. That's why I was thinking it was not the IACV. Anyway if you guys find yourself lost in Charlotte, hit me up, I'll reward with a drink or something. :D