hondamiser

PLEASE READ MY WHOLE STORY BEFORE REPLYING!

99 honda civic lx d16y7, 150,000 miles. Just had head gasket set replaced, when I got it back from shop, it idles at 3000 RPM, and burned 10.5 gallons in 197 miles. They had also replaced the distributor, wires, and spark plugs. They said it was probably the IACV sticking. I replaced the IACV, nothing changed, same very high idle, same sucking gas, half tank on 70 miles. When I first startup the car, it starts idling at 2200, then creeps up to 3000 in about a minute. It sounds like it's rough and missing too. After replacing the IACV, and seeing that it didn't fix anything, I stuck my finger over the IACV port inside the intake before the throttle valve plate, and it brought the idle down to normal (~600RPM). So, I'm thinking it could be a bad new part. I also tried unplugging the connector to the IACV, and it caused the high idle to fall to 1500 RPM, where it bounced up from, up and down 50rpm, as if it was hitting a limiter, and running rough, missing every 2 seconds like a pulse, in a steady rythym. (I'm guessing limp mode). Yes, I did bleed the air out of the coolant system by running the engine for 10 minutes without the rad cap on, refilling the coolant.

There is no CEL, but the light bulb for it could be burned out. I'm planning on exchanging the IACV for a new one and seeing how that goes, and seeing if there is a CEL code, despite no light.

09chaplak

Bingo compadre. Take it off and clean it, make sure the seat hasn't come loose and is causing it to stay open. There should be some piece inside the IACV with some threads.


That little guy on the right. Make sure that's almost seated and put it back on. Recheck everything from there

hondamiser

Actually, I think I listed the engine number wrong, it's a y7. The IACV looks like this, except mine's brand new, there isn't anything to clean on it. I had taken it off once to double check the gasket was fitting correctly and sealed. The throttle body side of the ports is clean.

hondamiser

I need to add...the high idle stays pinned at 3000rpm, it doesn't bounce around. I've read through countless threads about idling problems, but nobody had their engine idling above 2200 RPM, and nobody reported poor gas mileage. I noticed they say their engine ran steady when they pulled the connector plug to the IACV, but mine was rough. If something is causing the engine to run too rich, can this force the idle up high? It just doesn't make sense when the engine is hot, it still sucks air through the IACV port, but drops the RPM to 1500, rough, when I unplug it.

tony_2018

vac leak somewhere.

edit: reset the ecu and adjust your idle. disregard that statement above.

hondamiser

I'm crossing my fingers that it's not the ECU. I disconnected the battery for 10 minutes each time I fiddled with the IACV, so that has reset the ECU.

None of this was happening prior to replacing the head gasket. I think the shop goofed something up, but all they said was the IACV was bad. It's just that I've now replaced it (FOR $200!!!!), and it wasn't fixed. The shop doesn't want to see the car again, because they think I have a bad rod. (I don't care about the rod, i'm driving this car into the ground.)

tony_2018

Check your tps sensor to make sure its set correctly, make sure you aren't confusing the tps sensor plug with the map sensor plug.

hondamiser

How do I check that? It's riveted to the throttle body.
I did unplug it, and it just made the engine run the same, except that when i stepped on the gas, it made a whooshing sound and acted really lean.
I plugged it back in, and unplugged the MAP...no change at all.

Tempting to drive with the IACV unplugged, except when I stop at a light, it will sound really annoying...

I found this thread and the guy got a new IACV and it fixed it...his symptoms were identical with mine, except the fuel burning part...I'm taking the new part back to autozone.

https://honda-tech.com/honda-civic-d...-help-2877354/

tony_2018

Mods have created a FAQ section, you should check there

hondamiser

hondamiser

Went to autozone and exchanged the IACV last night, installed it, re-bled the air out of the coolant, NO CHANGE, STILL IDLES NOW AT 3500RPM!!!

I started unplugging things one at a time, the MAP, the ECT, IAT, both oxygen sensors, no changes at all.

FAQ no help.

The idle was so high this morning I couldn't press the brake pedal in far enough to shift out of park. I had to restart the car and shift into drive almost simultaneously.

hondamiser

many views, few responses.

turbohatch96y7

iTrader: (15)

Is the throttle plate all the way closed?

Ill help if you follow my directions to the t

First i want you to put your hand over the theottle body and starve the motor of air. Let me know if it dies or stays on.

Also post a couple pics.

Around the throttle body area, intake manifold, and a couple other shots around the engine bay.

hondamiser

Thanks for the response....

The throttle is all the way closed, the gas cable has a slight slack to it.

It will be a couple of hours and I can get to my car to try starving it of air.
I can tell you I put my finger in the port to the IACV before, and it idled perfectly then...I'm really tempted to block it somehow, but would rather find the real cause.

turbohatch96y7

iTrader: (15)

Cover the entire throttle body with your hand.

hondamiser

I fixed it.




I starved the engine putting my hand over the tb.

So, the I started poking around trying to figure out what it could be that was just in the throttle body area. Finally, I decided to fiddle with the adjustment screw for the throttle stop. It had been painted previously to mark the 0 spot, and seemed on the mark. But, the friction nut was already loose.
All I did was turn the screw about 1\4 turn to close the butterfly valve some more, and tighten the friction screw, and it's running perfect, idling 750, no roughness, no burning too much gas, etc!!!

I'm guessing the bad position of the throttle valve was throwing off the TPS.

Hope this helps somebody with a similar situation.