Hey All,

So I have been having issues with the idle on my car and I thought I would clean my IACV our, per the instructions that can be found on this site. I cleaned it out and during the process, I kind of broke the part on the IACV that connects to the harness connector. I did not break it completely off, but I think I might have broke one of the two wire connects on the connector.

So, after getting everything put back together, I started the car and it barely idles, fluctuates like crazy and I am getting a TON of smoke coming out of the tailpipe now. I also noticed I am getting a check engine light now. I have not pulled the code, yet. I will in a few.

My question is, will a faulty IACV cause the engine to run like this? Not able to idle, stalling and a ton of smoke coming out the tailpipe? I am thinking this is the only possability because the only things I did were clean the IACV and do a compression test. My compression came out 200/195/195/192 so I know the rings are good.

Anyways, please let me know ASAP. If it is a bad IACV, any recommendations on where to source a used one to replace it? The engine is a SOHC ZC. I am assuming its the same IACV as the D16a6?

Thanks!
-Jason

 

Lets Start With Getting That code first...Be 100% sure its the IACV and depending on your ECu is whether u can use a IACV from another model most likely a civic but you can also find that junk in a junker...besides that that sensor will cause a shitty idle but should run normaly considering that in a occasion i topped the hole in the throttle with a piece of plastic bag and it idled very low but it ran ok and then I brought it back to normal..

besides that this sensor should not cause any smoke out of the exhaust..


Now about that compression test... I cant tell you if those numbers are good because you havent told me your mod like if the head is milled or the head gasket,pistons or if this compreesion test was done cold or hot ect... but they are in close range within each other so it may be good

 

Compression tests are a little more detailed then just doing one. The very first puff can tell you if the rings are good, BUT, sometimes the piston in near the top of its compression stroke when you start the test on that cylinder so you will get a small first puff so it needs to be rechecked.

Also you need to monitor all the puffs and stop the starter on the same puff, for example I like to do 6 puffs only, not crank and crank and crank to get max compression. This is for a normal dry compression test, sometimes a retest is needed if I think the battery is drawing down as the test was progressing. Shown as lower and lower readings as you go along, mostly noticed on 8 cylinders more than 4.

 

Okay, so I found a couple problems that I somehow missed. First off, the TPS sensor was unplugged... oops. Second, one of the thin, black hoses leading to the MAP sensor was disconnected. I plugged these back in and now the car fires right up, idles and there is no more smoke from the exhaust pipe. I checked the ECU and found the following codes before and after these two fixes. I am seeing:

Code:

1 - Oxygen Content
5 - Manifold Absolute Pressure
7 - Throttle Angle

The weird thing to me is the check engine light is now off, but I am throwing the same codes after the fixes as before. I did pull the 15a fuse for the ECU in the engine bay, but is there something else that I need to do to reset or make the codes go away?

The car is running rich and sometimes the idle will sit at about 800rpms and then all of a sudden it will drop down to about 200rpms and come close to stalling out. I have been assuming this is a result of how rich it is running.

Can anyone tell me what would cause the number 1 and 7 ECU codes? The MAP I can figure out, but the others I have dealt with before.

Back to the compression test...

I ran this last night just because I had the gauge and had a few minutes to test it out. The test was ran with a cold motor, with the 15a fuse unplugged and with the injectors disconnected. We installed the gauge, floored the gas and cranked it over 5 times for each reading.

The longblock is totally stock internally, there has been no increase in compression via a thinner headgasket or shaved head. From what I have read over the years, 195-200psi seems like a good reading for a lower compression engine (9.0:1 ratio) with a decent amount of mileage on it.

I do have the basic bolt on's, plus a high boost JRSC setup, so I mainly ran the compression test to ensure the rings were still on the healthy side. I have a DPR prepped head that I plan on swapping on soon, so this should give me a bit more compression and power.

Thanks again for the help so far and please let me know about the code 1 and code 7. I need to figure out how to diagnose and repair these.

-J

 

7 is the throttle position sensor and 1 may still be there from you not properly clearing the codes, that goes for any codes you still have. I will assume you shorted out the CEL connector and got your codes to flash on the dash with key on engine off, just go ahead and disconnect the battery to clear codes for a little while, if they dont clear then you have a wiring or sensor bad. Your O2 sensor may be all sooted up right now, give it a little time to clear up.

 

Pulling the 3 ecu plugs is the best way to clear codes. 10-15 secs minimum.


If you cleaned any part of your intake system, you will have to reset idle. Unplug IACV, use the idle screw to set idle to ~400rpm, turn off car & reset ecu, replug IACV.

If you do that and it's still surging, you may have a vac leak elsewhere. Vac leaks commonly show themselves as surging idle. If it maintains a steady idle then drops/raises to another steady RPM, it may be bad contacts on the IACV (the ones you broke). Physically unplugging the IACV durring opperation should replicate the idle issues if that's the problem.

 

Dont forget that a vacuum leak can also be internal, not only a gasket leak, the IACV, FITV or throttlebody could be allowing too much air into the engine.

 

as could a bad valve adjustment or the mechanical timing being slightly off.

 

Easiest way to reset your ECU, beside pulling the back-up fuse, is to disconnect the (-) cable from the battery for 30 seconds. Remember that it will also clear your radio presets as well. If you have a factory stereo make sure you have the initialization code for it prior to disconnecting the battery..

I'm not sure that pulling up the passenger side carpet and unbolting the ECU plate so that you can unplug the ECU connectors would be the easiest way.

 

Yes, a bad valve adjustment can be checked by measuring the MAP sensor voltage going back to the ECM, 1V DC, a little less is best, with a digital volt meter. Bad mechanical timing can be seen with a vacuum gauge. An oscilloscope with a couple of attachments and some experience will show bad mechanical timing in a second but not everyone has one of those.

 

The map sensor at less than 1v at idle is probably the single most important measurement for a speed density honda.

The problem is most people like to just throw parts at their problem and not actually diagnose anything. You can lead a horse to water but you can't make him drink. There was just another thread a few days ago where the poor guy replaced the map sensor three times lol, the sensor itself rarely goes bad.