I have searched for this issue, but haven't found anything exactly the same as what I'm going through.

I recently purchased a 96 Civic EX that has been swapped to a D16y7 block/head. The y7 has a y8 intake manifold on it. I've been experiencing a high idle when the car is at normal operating temps of around 1400-1800 rpm.

I have already cleaned the IACV, adjusted the throttle cable, adjusted the idle screw, changed the position of the distributor, and bled the cooling system. I have also checked for vaccuum leaks by removing the intake and choking out the motor by covering the opening in the throttle body. I have also double checked that the MAP sensor and TPS are plugged into the correct harness since they are the same connector.

The only mods to the motor are an AEM short ram intake and full exhaust system.

I am at a loss here, and don't want to replace the IACV if it is not the cause of my problems. Does anyone have any ideas?

 

What ECU are you running? Is this an auto or manual car?

 

I'm not sure which ecu (or how to tell), but I'm going to guess it is the stock one. It is a manual trans.

Also, no CEL's. Have not tried to pull codes at this time.

 

Someone must have an idea that I haven't tried...Anyone?

 

Try spraying directly onto the joint between the iacv and the throttle body. My iacv gasket began to leak after cleaning and caused idle surge and high idle. Spraying would result in stalling for me. Check your intake gasket and tb gasket for leaks too.

 

Spraying carb/throttle body cleaner? I'll give that a try and see if that does anything. Thanks!

 

I'm starting to think it's timing or map sensor. Had another issue this morning (my first real cold start with this car). Wouldn't start at all. It would crank and catch but immediately die. Did this until the battery died. As soon as I hooked jumper cables up to my wife's Jeep it started and idled fine, but would die if you hit the gas. After it warmed up for about 5 minutes it was good to go. I need more ideas guys, this is driving me CRAZY!!!

 

Are you certain of this car's idle speed? Do you have an OBD-II reader that can give you stats on the car such as a Scangauge II? It's possible your tachometer is not working. However, I should ask, when you start up the car from a cold start and let it warm up, does the idle speed change at all? Ever? Does the engine fully warmup?



You're starting to think it's the map sensor based upon what exactly? You're jumping all over the place... Btw, if you can, get that battery charged by autozone and or buy a battery charger because you don't want to boost a battery since it's still very discharged and could not only burn out the alternator but possibly cause the car to not run correctly... (car electronics need a certain minimum voltage etc.)


When did this problem start to occur? Were there any other issues that were leading up to this issue?

 

check timing first. check spark plug order.

check idle cable tension. unplug iacv when its warm to see if its a iacv problem(idle will go normal) if it is

 

You can't unplug the IACV on a D16y7 motor because it won't idle properly if you do. That idea only works on the motors with the two wire IACV such as the Y8 and Y5 motors.

 

you learn something new everyday. i forgot i converted from 3 wire iacv to 2 wire


ohh he said he has a y8 intake manifold unless im high i just woke up

 

It has idled high since I got the car a couple weeks ago. I didn't think it would be this difficult to figure out though!

The car does fully warm up. First start in the morning it idles right around 1000 rpm and quickly goes up to between 1500-1800. I do not have a scan gauge but I can tell the car is idling high by the way the motor sounds.

I do need to replace the alternator and belt, could that be the cause of the problem?

I was guessing map sensor based on what I've read. Done a lot of research on this. Want to figure out the problem before I go throwing a bunch of money at it and hope something sticks.

I tried unplugging the iacv after it warmed up, still idled high.

Going to check timing this weekend.

 

ok. so unplugging the iacv did nothing. you sure iacv plug is correctly in. idle should drop when iacv is unplugged. try taking the intake off and plug the hole inside the throttle body with your finger and see if it goes down

 

The idle on my y7 does strange things when unplugging the IACV. I think last time I did it, the idle went up, but sometimes the idle does nothing at all. I suggest plugging the actual IACV hole in the TB. It will be obvious.

 

depends. when the car is cold the ecu send voltage to the iacv so it opens and lets in air to the intake so it can idle. once it warms up there is no need for extra air so voltages drop and eventially the iacv closes so it doesnt send any air. unplugging the iacv closes it so the idle should be perfect when the iacv is unplugged while the car IS FULLY WARM

 

i know on those y7 motors that little swing block off for air; can get plugged up a and stick open. i would take it off and give it a thorough cleaning and make sure the arm swings free and smoothly.

 

Did you play with the idle screw on the throttle body? The screw that holds the throttle plate open should have paint on it to indicate that it has not been tampered with.

 

Yes, we've messed with that screw. Put it back where it was though, didn't effect anything.

 

Sorry, what I meant was not the idle screw but the screw that adjusts the throttle cable position... That isn't suppose to be adjusted which is why I said make sure that the paint that is on that screw is intact. As for the electrical connections, have you made sure that you haven't swapped the IACV, TPS, and Map sensor wires at all? Maybe the power steering pressure switch? The knock sensor? These sensors use similar connectors and while I can't remember what connector is similar to what, I did remember one poster who had hooked into their knock sensor for their IACV at one point.

Maybe you should take a high quality picture of the engine bay or something.

 

This would be very difficult to do on a Y7. The TPS connector is an oval and doesn't fit into the nearby IACV. The MAP is on the other side completely and it would be ridiculously difficult to get it to fit in the IACV even though they are the same style plug.

 

Remember the OP said that this was an EX that had a Y7 short block swapped in, but that it retained the Y8 manifold. he's basically got a Y8 with non-funtioning VTEC.

 

yes he swapped in a y8 intake manifold i am sure it has something to do with wiring. maybe vaccum leak but that big of a vac leak would be heard very clearly

 

You might be surprised. My car had a vac leak between the IACV and the throttle body big enough to cause an idle surge between 1-2k rpm and keep the car running at 1k rpm with my hand over the throttle mouth and yet it made absolutely no noise whatsoever.

 

No vac leak, I took the intake off and covered the throttle body opening with my hand and it immediately choked out and died.