IAC hell

[lowinmo]

I have searched the forum and didn't find anything new.

The ride:
95 ex d16z6 manual
p28a02
hot air intake
6al w/ external coil
adjustable fpr
All else stock (for now)

Have been dealing with for awhile on my bro's car. He tried posting on here from his phone but it went retarded.

We keep getting a fluctuating idle. Bouncing from 1k to 1.6k, even after it warms up and this is the second motor in the car it's doing it with.

We have changed the IAC more then once and cleaned it. Changed TPS, Changed the intake. Using a manual both times. Flushed the whole system. Replaced the ecu with a known good. Changed the wiring harness.

This is driving us nuts. We want to resolve the issue before we put the piggy back on and turbo it. Kinda wanna have a solid starting point for all that.

HELP!!

[gcef89]

my car just now started this but i'm pretty sure its my tps if your throttle cable isn't adjusted right it can cause this to

[fry]

sounds like the wax in the throttle body issue. there are tons of write ups on how to fix this on honda-tech. involves taking the TB off and tightening a bolt on the bottom side of the TB

[stolle]

take off the fast idle air control valve, its under the throttle body, its got coolant lines gong to it. get some thin cardboard like poster board or something (your gonna make a gasket with it). cut it so it fits on top of the fitv cut holes for bolts, but make sure all the other holes are covered. Apply a thin layer of hondabond (grey rtv) over both sides of the cardboard gasket you just made and reinstall it. dont reinstall the coolant lines on the fitv or the iacv just get a new piece of hose and run it between where the fitv and iacv used to be.

enjoy

[JustRob]

take off the fast idle air control valve, its under the throttle body, its got coolant lines gong to it. get some thin cardboard like poster board or something (your gonna make a gasket with it). cut it so it fits on top of the fitv cut holes for bolts, but make sure all the other holes are covered. Apply a thin layer of hondabond (grey rtv) over both sides of the cardboard gasket you just made and reinstall it. dont reinstall the coolant lines on the fitv or the iacv just get a new piece of hose and run it between where the fitv and iacv used to be.

enjoy

Please do not do this. The FITV and IACV are there and require coolant to properly adjust and maintain proper idle speed at both cold and operating temperatures.

As long as you have no check engine light on, try resetting the idle speed first. Start the engine. Hold the engine at 3,000 RPM with no load in neutral until the radiator fan comes on, then let it idle. Disconnect the 2P connector from the Idle Air Control (IAC) valve. Start the engine with the accelerator pedal slightly depressed. Stabilize the rpm at 1,000, then slowly release the pedal until the engine idles. Check idling in no-load conditions: headlights, blower fan, rear defogger, radiator fan, and air conditioning are not operating. Idle speed should be 420 RPM +/- 50 RPM. Adjust the idle speed, if necessary, by turning the idle adjusting screw. Turn the ignition switch OFF. Reconnect the 2P connector on the IAC valve, then remove BACK UP (7.5 A) fuse in the under-hood fuse/relay box for 10 seconds to reset the ECM. Restart and idle the engine with no-load conditions for one minute, then check the idle speed. Idle speed should be 670 RPM +/- 50 RPM. Idle the engine for one minute with headlights (Low) ON and check the idle speed. Idle speed should be 750 RPM +/- 50 RPM. Turn the headlights off. Idle the engine for one minute with heater fan switch at HI and air conditioner on, then check the idle speed. Idle speed should be 810 RPM +/- 50 RPM.

If at this point you're still having idle issues it looks like, as others said, that the FITV may be the suspect as it's one of the main things that wasn't checked. To check this, warm up the engine (the radiator fan comes on). Check that the valve is completely closed. If not, air suction can be felt at the lower port in the throttle body. If any suction is felt, the valve is leaking. Check engine coolant level and for air in the engine coolant system. If OK, replace the fast idle thermo valve and recheck.

If the FITV is the issue, Honda does not recommend disassembling it. However, I have done this several times using the DIY link posted below without any issue. I would suggest doing this before buying a new FITV.

http://honda-tech.com/showthread.php?t=1564019

If you continue to have issues, post back with your results from what I posted above.

[stolle]

take off the fast idle air control valve, its under the throttle body, its got coolant lines gong to it. get some thin cardboard like poster board or something (your gonna make a gasket with it). cut it so it fits on top of the fitv cut holes for bolts, but make sure all the other holes are covered. Apply a thin layer of hondabond (grey rtv) over both sides of the cardboard gasket you just made and reinstall it. dont reinstall the coolant lines on the fitv or the iacv just get a new piece of hose and run it between where the fitv and iacv used to be.

enjoy

obviously this is not correct by any means, however i have done it many times and never had an issue with the iacv maintaining proper idle, cold or hot. not only that its cheap and easy.

Please do not do this. The FITV and IACV are there and require coolant to properly adjust and maintain proper idle speed at both cold and operating temperatures.

As long as you have no check engine light on, try resetting the idle speed first. Start the engine. Hold the engine at 3,000 RPM with no load in neutral until the radiator fan comes on, then let it idle. Disconnect the 2P connector from the Idle Air Control (IAC) valve. Start the engine with the accelerator pedal slightly depressed. Stabilize the rpm at 1,000, then slowly release the pedal until the engine idles. Check idling in no-load conditions: headlights, blower fan, rear defogger, radiator fan, and air conditioning are not operating. Idle speed should be 420 RPM +/- 50 RPM. Adjust the idle speed, if necessary, by turning the idle adjusting screw. Turn the ignition switch OFF. Reconnect the 2P connector on the IAC valve, then remove BACK UP (7.5 A) fuse in the under-hood fuse/relay box for 10 seconds to reset the ECM. Restart and idle the engine with no-load conditions for one minute, then check the idle speed. Idle speed should be 670 RPM +/- 50 RPM. Idle the engine for one minute with headlights (Low) ON and check the idle speed. Idle speed should be 750 RPM +/- 50 RPM. Turn the headlights off. Idle the engine for one minute with heater fan switch at HI and air conditioner on, then check the idle speed. Idle speed should be 810 RPM +/- 50 RPM.

If at this point you're still having idle issues it looks like, as others said, that the FITV may be the suspect as it's one of the main things that wasn't checked. To check this, warm up the engine (the radiator fan comes on). Check that the valve is completely closed. If not, air suction can be felt at the lower port in the throttle body. If any suction is felt, the valve is leaking. Check engine coolant level and for air in the engine coolant system. If OK, replace the fast idle thermo valve and recheck.

If the FITV is the issue, Honda does not recommend disassembling it. However, I have done this several times using the DIY link posted below without any issue. I would suggest doing this before buying a new FITV.

http://honda-tech.com/showthread.php?t=1564019

If you continue to have issues, post back with your results from what I posted above.

or you could do all that, just to come to the realization that fitv is bad then have to pull it all off again. Some engines have throttle bodies that have no provisions for an fitv, like a manual b18a1, d16y8s also had throttle bodies with no fitv. so if you wanted to you could hope to get lucky at the junkyard find one of the aforementioned TB's and swap out your TB with one that doesnt have an fitv effectively eliminating the fitv without using my ghetto cardboard gasket trick. then i suppose when you were finished you could still run a coolant line to the iacv so you could heat up the electrically actuated solenoid that your ecu uses to control the idle.

good luck!

[lowinmo]

Im going to take all this into consideration. On the plus side, I have a y8 tb sitting around.

[stolle]

Im going to take all this into consideration. On the plus side, I have a y8 tb sitting around.

use it, it will bolt right on, you dont necessarily need an fitv anyway.