TannerNCruz

So my car has been sitting for awhile, about a year, I've ran it quite often and made not to let the tires sit but a problem has come up in the past few months and I've been able to get together enough money to start getting it fixed. When I run my car, in neutral, and I get it up to operating temperature it begins to surge in rpms pretty steadily. Jumping up to about 2000+ then seeming to die but shortly reving back up to similar rpms. All in a matter of about a second or two. I've taken the throttle body out and made sure it wasn't gunked up with some MAF cleaner (CRC Brand) and it looks pretty clean. I didn't touch any other sensors or anything in the air intake system or the IAC. The problem persists. The only reason I hadn't touched the MAF inside the air system or the IAC is because I heard they were delicate and expensive. I plan on cleaning them the same way tomorrow and I can provide pictures to see if anything else seems to dirty, but everything seemed to be fine. If you have any suggestions as to anything else this problem could be and if it could be easily handled, such as cleaning the throttle body I can take care of it tomorrow, I'd love to hear it.

ezone

Vacuum leaks or IAC stuck open (sounds like).

IAC on the bottom of the throttle body? Get it surging, then tap on the IAC with something like a screwdriver handle and see if it changes anything.

There is no MAF, but there is a MAP sensor.

TannerNCruz

Is the IAC not on the bottom of the throttle body? That's where I was told it was. I can't acess it while the car is on, you mean tap the outside of it? What would I need to replace for a vacuum leak? TB and IAC Gaskets? Tried putting some new gas in and that might've made it worse. Can I clean the MAP sensor? Thanks for the help ezone.

ezone

I dunno, I can't see your engine. I was guessing.

Sure you can. Take off the big rubber air tube and run it.

Use your fingers to plug off the ports in the throttle body, the RPM should drop a lot. Does the engine nearly stall?
Report back what happens.
Which port did you plug to bring the RPM down?

Yes, tap on the IAC valve.

Don't worry about it yet.

That's not the problem.

TannerNCruz

Alrighty, I'll probably get to tapping on the IAC sometime the day after tomorrow. Thanks again for the help ezone.

TannerNCruz

Tapped on the IAC while it was surging. Didn't tap too hard but nothing seemed to change. Sorry it took me so long to reply, just started a new job.

ezone

....

TannerNCruz

Yeaaaah, I didn't get to that yet, just wanted to give an update so you didn't think the thread was dead. I'll be doing that tomorrow.

TannerNCruz

Just plugged both ports inside the throttle body the upper port didn't change the idle rpms but the bottom port for the iac when plugged brings the rpms back down to refular idle. Does this mean the iac is stuck open?

ezone

Could be......What does that passage lead to?

(I don't know all about your particular car (engine#, trans, etc) so I'm only guessing.)

Does the IAC get hot with good antifreeze flow?


Google and youtube for stuff about cleaning the valve, try to find about your exact engine and valve style if possible

TannerNCruz

I'm going to take off the throttle body and iac valve tomorrow and post some pictures. Do you mean does it get hot while the cars running? When I took out the throttle body there was coolant in the iac but I didn't remove it nor have I changed the coolant in awhile. After taking it out and cleaning it I'll probably do an idle reset and see where that takes me.

ezone

The water passages into and out of the valve need to have good free flowing antifreeze circulation, the FICV (still assuming yours may have this type of IAC) relies on this flow to adjust the fast idle down as the engine warms up. If liquid flow is poor, slow, or nonexistent, the FICV would stay wide open because it cannot sense the engine is getting warm at the proper time.


Not only the water passages of the valve itself, but the rest of the system needs to have good liquid flow. I've seen the nipples elsewhere on the block and manifold (and various other places on different cars) get blocked with crud, rust, even stopleak. Any restriction at any place in the system can cause problems.

TannerNCruz

So I took out the TB and grabbed my engine number (d16y8). I took off the IAC and sprayed it with MAF cleaner. When it was off the valve was slightly closed so don't know if that means it was stuck or not but I pushed it open all the way. My coolant that was flowing through it is still green though it may be low now since I lost some in the removal process. (Sorry for the links, imbedding wouldn't work and couldn't upload due to file size.)
http://imgur.com/br4zIpl
The red circle indicates the port plugged which caused the RPMs to regulate. The Blue is just another port which bypasses the plate.
http://imgur.com/aIh8nRF
This is the IAC itself. The yellow arrow indicates which way the air flows through the valve after passing through the port. The blue arrow points to the plate that opens and closes within the valve and the red arrow is where the coolant flows through.
http://imgur.com/WBByLr1
This is the back of the throttle body. The yellow circle is the map censor port. The blue circle is one of the screws keeping the MAP censor on, it seems to have calcified but I don't believe air flows through it so I don't think it's a problem. The red circled area is just where the upper port leads too. Thought it lead to a censor but turned out it didn't.
http://imgur.com/eADvxfC
This is the side of the IAC. I haven't touched the circled area because I was told it was delicate. This was the closest (looking) thing I could find to the FICV. Don't know if there's a little plunger inside it or not but I couldn't find a FICV on the intake manifold and there isn't anything else attached to the throttle body.

So I think tomorrow I might try topping off the coolant since it didn't look too dirty and reattaching everything. Might try spraying cleaner to check for leaks in the gaskets but other than that I don't know what else to do to check the IAC or find the FICV. Hope some of this info is helpful. Thanks again for all the help.

TannerNCruz

Ohh did a little research. My model doesn't have a FITV. Don't know if that's the same as FICV but I figured it was.

ezone

Use something like a toothpick to push on the rotating valve (blue arrow - chambers area, it's like a round tube inside with slots cut out and it rocks back and forth as it operates to change the size of the passage), see if the valve is stuck in the open position.

Note that it is spring loaded to a certain position, but it should be free to rock back and forth when the motor operates.

TannerNCruz

Sorry for such a length between replies. New job, school started. Blah blah blah, life sucks. So I cleaned the IAC valve, it was free to rock back and forth, put a new gasket on it to ensure zero air leakage, and did an idle re-learn every single way I could find how to on the internet. No avail. Still have the same idle problem. Had a friend come look at it, (he's a diesel mechanic) and he said he didn't think it was a vacuum leak because he definitely didn't hear any, he said it could still be possible but with the RPM drop from plugging the IAC port it's doubtful. He also turned the idle screw a bit, causing the surging to change into shorter intervals. We quickly put it back to where it was because the surging seemed scarier in such short intervals lol. Any other suggestions before I shell out the 130 bucks for a new valve? Thanks so much for the help, hope I can get it running correctly soon.

ezone

Turn that screw inward (clockwise), see what happens.

Does the car have auto trans? IAC has 3 wires?

Engine hot and running, disconnect the wiring from the IAC. What does the idle RPM do?



Have you opened up the ECM yet? Look for leaking capacitors

TannerNCruz

Turned the idle screw while the car was running, nothing happened. Yes it's automatic, yes three wires on the iac and when disconnected it causes the shorter interval surging. Very rapid. I don't quite know where my ecm is, but I can look around if those two things don't tell you anything.

ezone

Ok some of the next steps involve testing the wiring between the IAC and the PCM for continuity and shorts to ground,

and ohm test the IAC valve, center terminal to eqch outer terminal should measure 16-28 ohms



PCM is behind the passengers kick panel.