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So here is my problem. I have a 97 civic ex with a d16y8 an I just replaced the engine same size. After the swap the new engine would not idle and cant seem to figure out the problem. The engine runs great and iv tried to do everything I know how to figure this problem but now im lost everything I do isn't helping. Its jerky on take off around 1000 to 2000 rpms an when around the same rpms it idles up an down.It keeps throwing the same codes p1508 wich is the IACV witch im really trin to be shure is the problem before I replace it. Its also throwing misfire codes p1399 and p0302. CAN ANYONE out there please help me, what am I missing?

 
Rep Power: 174

Have you tried removing and cleaning the IACV? How do your spark plugs look?

 
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For the misfires Change your spark plugs, check your wires, replace wires, bad distributer? Try tapping the idle control valve while the car is at idle. If your rpm fluctuates or changes try taking it off and cleaning it, they can get clogged with carbon deposit causing it to stick open or close which in turn effects the idle. Check for vacuum leaks as well.

 
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The distributor plugs, wires are all new. Iv cleaned the IVAC with no luck, checked for vacuum leaks can't find any, adjusted valves an the misfire stoped for about 200 miles( that's two days of driving to work for me) bled the coolant system. Ran compression test 150 on all cylinders.When it idles it's eather to low or to high around 200 rpm to 2000 rpm never where it is spose to be. Bumping the IACV doesn't help nether. My gas mileage sucks to it drinks gas like a V8. Iv worked on Hondas before but not for nothing like this I'm hoping it's the IACV if not maybe something cheap.

 
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And when it misfires an throws the code I can't feel or hear a diffrence so it's not a constant misfire iv adjusted the timing as well.

 
Rep Power: 174

How are your oxygen sensors looking? Specifically, the one closest to the header?

 
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I replaced the o2 when I bought the header because I rounded the one on the stock manifold but that was before the swap and I put it on a live feed reader it would fluctuate between 0.075 to 0.900 something is that normal for an o2? An how could I find out what the normal readings are or spose to be?thats the one thing that stood out to me. An would it cause it to throw an IACV code? I know a bad o2 will cause a misfire it wouldn't surprise me if it would code an IACV. An my luck it would be that simple after the headache.

 
Rep Power: 174

Nah, the sensor's supposed to fluctuate like that.

I doubt it would throw an IACV code. I think IACV is your best bet, although it IS weird that adjusting the clearance at least temporarily fixed your problem. Is it possible that they could be out of whack again?
Also, how does your EGR look?

 
Rep Power: 0

The EGR is my next step I used the one of my old motor I'll try an get one today. As for the valves I'll check it again I was planing on it anyway, but what could knock it out of adjustment?

 
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Is it loosing coolant? Overheating no? Could be anything dirty fuel filter, cap and rotor, or throttle position sensor.. Also on these Hondas the engine has to be dead cold when you do the valves..

 
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Ok so the civic decided it wanted to give me some more issues. Wile driving down the road the car stalled and wouldn't do anything, the car was still running but it wouldn't throttle up even if I put the petal through the floor it wouldn't give nothing an would eventually die, and no new codes just the same p1508. Good news is that I believe that I found my misfire. New distributor and when you take the cap off you can see where the rotor is digging into the cap really bad at the cylinder 2 prong. As for the IACV im getting power threw the harness and I stuck a power probe to the IACV and it seems to do what it is spose to do no problem so that where im at. As for the EGR I cant seem to find it unless it is called something else but it should be on the intake manifold right? My engine is the d16y8 vtec and another thing, where can I find the normal live data reading for the car?

 
Rep Power: 0

Check your grounds.! My ground was bad under the thermostat housing and I had similar issues. Two black wires bolted to thermostat housing.. Also could be a clogged catilitic converter

 
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Ok so I checked my grounds an all are good, and took a punch threw the cat still same problem. What isn't right to me is that I can put 12v straight to the IACV an it will work so I don't think it is bad. I found another IACV and it still does the same thing. Im getting 12v from the harness but for some reason its still not working and keeps running like crap an keeps throwing the same code. Could this be a bad PCM? What am I missing?

 
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Know what it is..! Its your pcv valve 3$ part! Positive crankcase ventilation. . This being clogged could repeatedly clog the intake. the pcv gets clogged and needs to be replaced.. shake it after u remove it, if it rattles its still good. If it doesn't move, replace. You will get better gas mileage and burn less oil. When these are clogged on hondas they start a chain reaction of destruction. . Car gets worse mileage burns more oil cloggs iacv effects idle .. this part goes unnoticed at shops because there's no money in replacing 3$ parts also its located under the intake manifold , where it meets the head. you have to know its under there to even see it ..good luck getting it out but it should fix your problem!

 
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Yeah iv fought with one before the symptoms are close but in don't remember it being as bad but you never know. But I wouldn't think that a bad PCV valve would cause it to throw a IACV circuit malfunction code. Wouldn't the IACV still work tho with it getting power?

 
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I had a very similar problem a while back. You might want to check your FITV. It is directly under your throttle body. You can clean it out and carefully put it back together making sure to screw the inside plunger all the way down. The following link might help you:


http://honda-tech.com/acura-integra-...valve-1564019/


make sure to bleed the coolant afterwards, or you could end up with an air bubble.

 
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I believe its my computer it's the only thing that makes any sense. I haven't had much time to fool with it lately. Iv cleaned all components dealing with air intake and fuel delivery but the problem continues so iv ruled that out. What didn't make sense to me is that I could put 12v to the IACV an it would work and I was getting 12v from the harness. I checked the wire for resistance an all is good but it still wouldn't work, but I can probe the harness where it connects to the PCU and send 12v threw it that way and it will work so for some odd reason my PCU is not sending enough voltage an not letting the full 12v work the IACV. Im gonna try a computer if I can find one. I believe it MAY be my problem.

 
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I have basically the same thing on my 97 Lx.
Took throttle body of to clean it due to intermittent rogue high idle.
Cleaned everything real good, and know I have a idle that is similar to this. Kind of like someone stabbing the pedal real quick. It threw a code also, so will get it checked in the morning.

 
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Bad pcv wont throw a code alone, but it will throw the iacv code frequently , from dirtying up the intake