I have a '94 Accord LX basket case that I'm trying to get going. I bought the car with a blown head gasket. Had the head surfaced and put a new gasket and head bolts in. Replaced the thermostat, plugs, wires, cap, and rotor. Previous owner had put an ignition coil and EGR valve, and a different throttle body on it so I'm guessing he was fighting the same issue. Also replaced the Auxiliary Air Valve on the bottom of the throttle body with no changes. Pulled the IACV off and it was clean. Removed throttle body and cleaned all ports in it and both sides of the butterfly.

Car will start and idle fine when cold. Holds steady at around 1500 RPM then slowly drops as car warms up. Originally, it would run for around 25-30 minutes before it started acting up. Fans would cycle so I knew the engine was warmed up to operating temp. Idle would start to surge (800-1200 rpm) but if you tapped the throttle it would come out of it. Then it would slowly lose RPM to the point of stalling. Tonight, I replaced the TB gasket and cleaned everything I could on it. It seemed to happen a lot quicker than before. When I started it, the idle was low instantly. Ran for about 5 minutes and tried to stall. Have to hold the pedal at about 1/2 throttle to restart once it dies. I have checked all the vacuum lines and can't find any issues there. No check engine light ever comes on at all so it's leading me to believe it's something mechanical. I can unplug the IACV and it has no distinct change in the way it runs at all, but it will set a CEL then.

Thanks for any info guys.

 

Remove and clean the IAC valve....back side if the TB and different than the FITV you speak of.

Properly bleed the cooling system to be sure there is no trapped air....when you replaced the FITV there should have been coolant in the lines?

Check for any stored codes.

Pull the fuse for the ecu/tcu. Replace after a few seconds (30~60). Start the car and do not touch the gas pedal. Let is run...poorman's idle re-learn, Jim has a write up for the true process.

 

Already removed the IAC Valve. It was visually clean.

No air coming out the bleeder screw so I'm assuming it was bled properly. Yes, there was coolant coming out of the lines when I replaced the FITV.

No codes flash when the connector under the glove box is jumped. I'll try the idle relearn again and see what it gets me. Thanks.

 

Is the base idle ~550 RPM with the IACV unplugged? There's a sticky on setting it:

Setting Base Idle speed

 

After I worked on it the other evening, it seems to idle about there no matter whether the IACV is plugged in or not. I had removed the throttle body, thoroughly cleaned it, replaced the gasket, and reinstalled everything. I didn't reset anything after installing the throttle body. Maybe that was part of my issue at the time. It immediately idled low once I started it up, to the point of barely running. It then idled up to around 1300 or so like normal and slowly started to come down. After about 5 minutes it was at the point it would not idle unless you held the accelerator. At one point I was able to unplug the IACV with no noticable change in idle speed at all. It set the CEL, and then I noticed I had a coolant leak at the hose going to the FITV so I shut it off and walked away. I knew it would do no good to keep running with the hose leaking. I need to get a new spring hose clamp, or possibly put a normal worm gear type on it before I can try anything else.

 

Might think about testing the IACV....the valve and the inputs to it. If no change when plugged in or not leads me to wonder if it is working or getting the proper input.

Get the hose replaced and be sure to bleed the air out of the cooling system using the proper procedure and we can go from there.

 

Ok. Replaced hose clamps on the coolant lines to the FITV. Bled the cooling system. Reset the ECM. Started perfectly, idled at 750 RPM for about 45 minutes with no issues and no CEL. I pulled out of the driveway and made it about 2 blocks down the street and if I let off the accelerator it will stall. Have to hold the accelerator down to get it to restart and then two foot it back home. 12 volts on one side of the plug, and 10.2 volts on the other of the IACV. I removed the valve again and cleaned it again just in case. No change whatsoever. Idle with the IAC unplugged is about 650-700 going by the tach. Doesn't seem to change when you plug the IAC in. I'm leaning towards a bad IACV but figured I'd see the opinions here. Thanks.

 

Take a closer look at your tachometer. The first mark past 0 is 500, then 750 rpm. There is no 250 rpm mark.

As for the voltages, tell us the wire colors along with the voltage. Also, what is your black lead on the volt meter touching for ground? There are three wires going to the IACV, so tell us the readings on all three wires.

 

I realize there is no 250 Mark. It's above the 500 mark and below the 750 mark. Since I don't have a digital tach to get an exact I'm estimating it to be in the 650-700 RPM range. Black lead on the volt meter is on the negative battery terminal. My IACV only has two wires. 3 wire IACV's didn't start until '98.

 

X2. The FSM has page after page of diagnostics but IACVs are cheap and plentiful at junkyards.

Being a cheapskate I'd try one more test to see if the solenoid is dead: 12v on on the YEL/BLK pin of the disconnected IACV connector, then momentarily tap the BLK/BLU pin with a ground wire. Listen for the solenoid clicking.