rujoesmith

98 civic ex
d16y8 engine
143k miles

I recently replaced the head with a re manufactured head from J&C enterprises

http://www.ebay.com/itm/271294489916...84.m1423.l2649

It runs great other than the idle problem. Once the engine warms up it fluctuates between 1 and 2k. Also when I lightly depress the gas pedal it starts fluctuating faster. once i get over about 2k it runs smoothly until i let off the gas. Whenever i let off and then re-accelerate it jerks like i just tapped the brakes.

The CEL coded is p0505 idle air control system.

Things ive tried so far:
removed the idle air control valve and cleaned with brake cleaner, as far as i can see there is no carbon at all left in there.

warmed up engine, Reset ecu and allowed it to idle by itself for about 15 minutes.

bled cooling system and made sure it was 100% full

Not my video but this is almost exactly whats happening:

ezone

Remove air tube from throttle body
plug off the open ports with your fingers

Does the idle drop to normal?
Does the idle drop waaay too low?

If no drop or not much drop, then look (listen) and test for vacuum leaks

rujoesmith

Just did that, but nothing really changed so ill look for vacuum leaks tomorrow. also while i was out there i unplugged the iac valve and the idle jumped up to about 1700, seems like i read somewhere that if disconnecting it increases the idle speed then theres most likely not something wrong with it.

ezone

When the valve is disconnected, the engine speed is supposed to

increase -- A/T and D16Y7 engine
decrease -- D16Y5, D16Y8 with M/T B16A2

(According to the info I have)

rujoesmith

Ah, maby that could be the problem then. A friend thought it might be that but i was thinking it was something i just put back together wrong considering this wasnt a problem before i replaced the head

ezone

No, it isn't the problem.

You eliminated the IAC when you plugged off the holes in the throttle body--- yet the engine kept running too fast. (Assuming you did that correctly.)

Keep looking. I'd expect vacuum leak(s).

rujoesmith

I saw a video where someone unplugged a tube and started blowing cigar smoke into it in order to find the leak. would you recommend that or will it damage something?

ezone

Depends on your choice of smoke


You found a Scotty Kilmer vid? LOL
As humorous as he can be, no, it won't damage the car.


[autostream]http://autostream.com/ibcivicforums/?page_type=firebirdplayerthumbnail&framepage=1456& transactionid=1385134278-173167166182&posted_by=_www.civicforums.com&youtub e_video_id=9CPqbaSgcok[/autostream]

http://www.popularmechanics.com/cars...-a-vacuum-leak

http://www.popularmechanics.com/cars...-vacuum-leak-2

rujoesmith

Well i looked and looked but cant find a leak. But now when i put my finger over the hole in the intake that goes to the iac valve, the idle speed drops waaaaayy down. Does this mean bad valve? the manual i have says to adjust idle via the idle adjust skrew or replace the valve if not possible

rujoesmith

is it possible the connector is bad? because 2 completely different things happen when i unplug the iac and when i plug the hole in the intake.
take out connector = much higher idle
plug hole = very low idle

ezone

It does not necessarily mean the IAC valve is bad, you have only proven that the engine is running on all the air that goes through that passage..

There are other things that can cause the valve to be held open too far, namely the computer seeing incorrect inputs.... or something.
(GIGO <----Look that up if you have to.)

That's why I want to know what the computer is doing.

Have you tried that adjustment?
(I didn't think of that until you said it, the screw adjustment doesn't cause high idle problems unless someone really tampered with it.)

So look at it. Does it have fresh marks on it like someone just had a screwdriver on it?

Yours may be in a similar location if it has one:




Note (count) how many turns you move the screw. If screwing it in doesn't solve the problem, you need to put it back to the same spot it was in (because changing it will just cause more problems if it wasn't the original problem).

Read this again:
It did something when you unplugged it. Your electric connection at that valve appears good at this time.

Copied from above: you have only proven that the engine is running on all the air that goes through that passage.

You still gotta figure out why.

EDIT: How low does it idle with that hole plugged? I thought you said the other day it made the engine stall.

rujoesmith

Wow thanks for all the info and pics!

I actually tried that today. Warmed up engine, removed the iac connector and turned the skrew all the way to the right and that still only gets it to about 1200. So i put it back where it originally was.

Before it diddnt really do much, im not sure why it did something different this time. But it never actually stalled, this time it just made the idle drop way down. I never actually looked at the rpm's, but i could.
Also, there was quite a bit of suction coming into the hole, i could hear it whistling and it left a circular mark on my finger when i pulled it off. Not sure if that's what supposed to happen or not.

ezone

Seems like this is coming back to me wanting to know what the computer is seeing.

A capable scanner is my best friend.


It could be stuck partway open, can't close completely (but can go wide open).



It's supposed to be that way. There's 20" of vacuum there.



Have you tried tapping directly on the IAC valve yet?

Have you cleaned the snot out of the IAC?

Please read this thread, there's a ton of my thoughts in it. Scooty had a similar problem even after cleaning his IAC---It took multiple cleanings before he got his working right. Somewhere around post #40 he finally got the answer
https://www.civicforums.com/forums/1...worse-now.html

rujoesmith

nice ill read through that thread and try all that tomorrow. But currently i have an obd2 cable going to a built in computer which is running dashcommand. Maybe i could download some software and get any helpful info?

heres the link in case ure interested:
http://www.mp3car.com/show-off-your-...d-install.html

But no i haven't yet tapped on the iac yet, i cleaned it once, but ill do it again and also try soaking it like the guy in the other thread.

ezone

I just realized I was thinking this was a different thread on some of my replies.


Is the engine reaching operating temperature (180*-210*F as displayed in the PCM data)?

Does it still surge even when the engine is at operating temp?

rujoesmith

According to the reader the coolant temp is at 200-210 when warm. But it only starts surging once it has reached operating temp. When its still cold it holds idle at around 1200 with no surging.

ezone

OK that sounds normal and correct (within reason) to me.

Back to the IAC valve itself and/or its controls.

rujoesmith

Well im not really sure what happened, but a couple of days ago i started it up in the morning and its been running much better but not perfect. Theres no more surging and it idles right around 750 when the car is warm. But whenever its cold it idles at almost 1800, which seems a little high.

I cant remember if this is what it used to do but whenever im driving and i shift to neutral to coast, it only goes down to 1200, then down to 750 when i come to a stop.

ezone

They are supposed to idle fast when cold, and the colder it gets the faster it may run.

The 1200 RPM while rolling might be normal, it's been a long time since I drove one of those with a manual trans and I can't remember for sure....but it sounds OK to me, some cars are programmed to be that way..
If it comes down to normal idle speed when you stop rolling and you have no other issues, I'd call it good at 750 @ hot idle.

rujoesmith

Nice! well thanks for all ure help