whyS0serious

I have a 98 civic ex idle problem.

When the car is cold it revs up to 2k rpm then fluctuates up and down, but once the car is pretty warmed up it idles smooth like nothing happened.

- I cleaned the iacv and reset the ecu
- bled the coolant
- checked for vac leaks

Any other suggestions? please let me know thanks in advance

silkypillows

any cel's? d16y8?

whyS0serious

No cel and yes its a d16y8

ill prob pick up iacv at a junk yard and clean it to see if its that if not then....

Former User

Does the CEL work? An idle problem like you describe should throw a CEL code.

whyS0serious

Yes cel works when I took out the plug to the iacv the cel turned on and the idle went high but I plugged it back reset battery and its the same

Former User

When the idle is hunting, remove the air intake system and then use your finger to cover the hole leading to the IACV inside the top of the throttle body. Does this drop and steady the idle speed?

whyS0serious

yes it steady the idle speed.. OH and btw once it at steady idle you can hear this loud buzzing noise coming from the air intake

Former User

What happens to the idle speed and behavior when you unplug the IACV?

whyS0serious

When i unplugged the iacv it stays above 1k rpm and cel comes on

Former User

Does your car have an automatic transmission?

whyS0serious

manual transmission

Former User

Are you saying that unplugging the IACV had no effect at all on the idle speed or behavior (compared to when the IACV was plugged in)?

whyS0serious

no,
When its plugged in the idle speed goes above 2k rpm and starts to fluctuates... after the car is warm it goes to idle speed.

when its not plugged it stays above 1k rpm and just stays there not even moving w/o fluctuates

Former User

What is the idle speed after the engine warms up?

gotcha

whyS0serious

when its warm its at normal idle speed around 600~800

Former User

Is the coolant level low in either the radiator or reservoir?

Have you thoroughly bled the cooling system like this:

https://honda-tech.com/forums/showth...1#post39830585

whyS0serious

yup did exactly what you posted =]

Former User

I'd recommend that you bleed the system again. I think there may be air trapped in the cooling system.

If the problem persists, then test the ECT sensor and the TPS.

It would probably help to hook up an external tach or scan tool to get a precise reading of the idle speed when the engine is fully warmed up.

whyS0serious

alright thanks ron for your help i'll bleed the system again

Former User

Good luck.

whyS0serious

So i found out the problem with the idle fluctuation.. and btw i gave out some wrong information sorry =.=...
correct information
i have
swapped a 99-00 d16y8 engine into my 97 civic cx
using 96-98 civic ex engine harness
using a 96-97 Del sol Si ecu (using it because it doesn't have the Fuel Tank Pressure Sensor on the gas tank)

so the problem was the FIACV (Fuel Injection Air Control Valve) I plugged that off from the intake manifold and the idle fixed! no more idle surge from cold start.. the 99-00 civic has the FIACV and the 96-98 civic doesn't have that valve

chillerice

Ron I have had this similar idle issue only that my car is auto. Cleaned TB,IACV and check for leaks also. D16Y8.

Happens every cold start and smooth out at normal temp. Only that my tach reads like 450-550 at normal idle. No CEL on but it comes on if I unplug the IAC. I've had this for months to the point now if load goes on the engine the tach goes up but no matter what gear I'm in it drops back close to 0.

weezie41

ive had the same problems with my 1993 civic d16z6 and cleaned the same components and just so happen checked the distributor cap and Bam their it was the cap was the problem so check it out.