I am stumped. I have a 1991 Civic DX converted to MPFI w/ D15 engine.

I am getting a code 14 which is the IACV. I have cleaned the IACV and also replaced it. I can also hear the valve opening and closing via a metal rod when the engine is running. The car does not idle, it just dies. To bypass this I have set the throttle cable to hold the throttle body open very slightly to idle. What can be causing the IACV to not work properly?

The second problem is the hesitation. When the car is in open loop(cold) it runs perfect minus the idle problem. As soon as it hits closed loop(warm) I get a horrible hesitation from idle to about 3000rpm. So this, for the most part, rules out ignition/fuel problems and timing, it has to be a sensor but I am not getting any codes other than IACV(14). I also get a small sputter right around 5000rpm.


Steps I have taken so far...
Cleaned IACV
Replaced IACV
Replaced O2 sensor
Replaced PVC
Replaced rotor button
Replaced distributor cap
Replaced plug wires


What is wrong?

Thanks, Nick

 

Sensors have varying degrees of failure, and they have to fail quite badly to trigger a CEL. So this could be something that is partially failed. I'm guessing you should check out the TPS and MAP sensors, false readings from those can sometimes mimic other problems.

 

Thanks Chris, i was waiting on you and a few others from here to give me some input. I will test those two out once I get back to the garage.

 

If you have access to a factory manual, or can download one in pdf form, the factory manuals usually have pretty good troubleshooting flowcharts and stuff like that in them. I've had good luck with that, especially narrowing down the likely suspects before you even start testing stuff.

 

have you recently switched plugs on the back of the manifold around?


b/c i know some of the MAP, TPS, IACV etc... have almost the same fucking plug design. try switching the plugs around, or look on a wiring diagram, to figure out the color code to make sure the right plug is pluged in the right sensor.


i've done this many times, and had the same problems.!!

good luck

 

Update.

I have resolved the idle issue, it was my own stupidity. Plug was incorrect, dorko was right on the money.

I decided to check the voltages of my TPS. It was way off, I replaced this and set it to .45/4.5. Unfortunetly, the hesitation is still there.

I then discovered I had a leaky injector, I replace that with a working injector. Hesitation still. And yes, I reset the ecu after each "fix" to see the effect.

I am going to start tracing wires tomorrow and see if I can find something.... not sure where to go if there are no problems there.

 

i swapped mpfi in my civic a while ago and also got hesitations. never figured it out, but once i swapped b, it was gone

 

Well, the hesitation wasn't there when I did the conversion. This is way after.

 

at least you found one of your problems.!!

 

Final update.

So, after about 12 hours of work and ~$150 in parts, I found the problem.





































































It was a fucking spark plug. Part of the porcelain around the center electrode had chipped off (blows my mind how that happened). I replaced it with another plug, and now it runs beautifully. Thanks for the help.