Ej1203

Hello Hondatech, I need your help, I'm running out of ideas and this car is driving me crazy!!

i own a 1995 Honda Civic Ex, it is completely stock, no modifixtions with the original motor. The car sat all winter as I don't want it in the snow, however I would start it and let it run atleast once a week. The car had an oil leak, so last month as the weather warmed, I took the car apart to replace the oil pump o-ring,
reseal the oil pump to block With Honda bond, replaced crank seal, oil pan gasket and valve cover gasket and degreased the engine. I also adjusted the valves while I had it apart and replaced the air and fuel filter. I started the car with the power steering pump disconnected as I had a reseal kit because the P/S was getting noisy. The car started right up and and sounded better than ever, I backed it out of my garage and let it run awhile to confirm no leaks (didn't drive around due to P/S pump being off). The next weekend I had more time and I rebuilt the powersteering pump with all new seals. I installed pulp and started it up, I immediately got a CEL (#14 IACV code) and the idle was surging from 1200-1600 RPMs. Since then I have tried to following to resolve this strange idle issue with no luck:

-Disconnect P/S pump and start car (although pump sounds great and works fine, maybe too much pressure? Causing strange idle)

-remove throttle body and clean and adjust fast idle valve and replace throttle body gasket

-sprayed carb cleaner around all of intake manifold and PCV lines with no obvious change idle speed


-checked TPS vintage, no dropouts along entire throttle range

-confirmed good power and ground at IACV plug

-replaced IACV with brand new OEM Honda part

When the car is on, I put my finger over the bottom hole in the throttle body and there is very little suction(good because car was warm- cold idle valve should be closed) however the upper hole for IACV is sucking air had and loud, when I cover a majority of that hole is idles normal.

The only thing I can think of now is pulling intake manifold and replacing intake manifold gaskets and all the PCV hoses and PCV valve. Does ANYONE have any idea on what could be causing my issue, thank you!!

mk378

One big reason for surging idle is not having the cooling system completely full. Any time you drain-refill it you have to get the air out completely.

Unplug IACV, it should slow to less than normal idle. The IACV springs closed with no power applied, and opens on command of the ECU driing the black/blue wire to ground (the yellow/black wire is constant +12)

Ohm test the old valve. I think it's supposed to be 10 ohms or so. Code 14 will be thrown if open circuit.

If it does not slow down with IACV unplugged, find out how the air is getting in. If it does, ohm test the ECT sensor the ECU may think the engine is cold due to bad readings from the ECT. When it is cold it should fast idle.

Ej1203

thank you for your detailed response, to be clear, even after installing the new IACV the CEL remained on even after unplugging battery for 10 mins..I have already unplugged IACV and the car does return to a Normal idle speed (which makes sense after your explanation on how they are powered).

I will check the ECT sensor tonight, as well as bleeding the cooling system again.

mk378

You could have the black/blue wire shorted to ground, causing IACV to open whenever it is plugged in whether or not the software wants it to.

Also if during your work on the engine you unplugged any of the sensors, realize that the various 2-wire plugs are not "idiot proof". They can be plugged into the wrong things. You have to check by wire colors.

Ej1203

Yea I know what you mean regarding connectors, however I hadn't disconnected them and I have double checked them to confirm they are in the proper spot.

I did disconnect the ECT sensor and test the resistance with the sensor still in the motor.. reading was .545 M Ohms which I'm thinking is .5 megaohms. Comparing that to the Haynes manual leads me to believe maybe the ECT is faulty.. thoughts on the attached pictures?

mk378

Yes, that is bad.

Ej1203

crazy man, my buddy was junking his 1997 civic with blown motor and I took his ECT sensor out and tested the resistance and I got .500 M ohms.. now I'm questioning if that's what's wrong, Honda ordered me one today but I'm friends with the guy and said if I didn't need it then it's fine.. I think I'm going to take mine out and test it in hot water.. this dam car is driving me crazy

TomCat39

If your meter isn't Fluke or some other high end meter, cross your leads on the resistance and see what you read. It very likely is not zero. Whatever it is, that number should be subtracted from your results to get the actual reading of the component you are testing the resistance of.

Ej1203

hey all, just as an update- I ended up testing the harness and all the sensors with no luck. I ended up taking the ECU out and apart and I found a capacitor had let go and damaged that circuit (pic below). Ended up getting a ECU off someone local and it works perfect now.. ordering a cap replacement set for my original ECU off eBay and my buddy and is gonna resolder all the caps and I will have an extra computer. Thanks everyone for your input!

vstro8oy

I am having the same issue now and was wondering what the process what like in repairing your old ecu. I don’t really wanna fork out the money for another and have no idea where I can send my current one for repairs. Will it be worth the effort to repair mine or should I save the headache and buy another ?