'91 Civic EX sedan, D16A6 engine.

I cleaned my IACV yesterday. While I had it off I measured the resistance and got 1460 ohms! I read its supposed to be 8-15 ohms.

Do I have to replace it?

 

is it causing a problem? if not then i would leave it alone.

 

Not sure, I think its causing the idle to drop for a short period whenever I put the auto tranny in gear or start anything electrical like power windows, locks, ac, etc. Idle also drops when I push the brake (which seems to trigger a click noise in the shifter area)

 

It sounds to me like your battery is getting old and can't sustain the draw, or your alternator is getting ready to go out.

It could also be that your brake booster has a major vacuum leak. you can test it if you have a vacuum gauge.

Luckily, you can test all of these things without spending any money. You can test the specific gravity of your battery with the "turkey baster" specific gravity tester, and the brake booster can be tested by capping one side of the vacuum line to it and using a vacuum test pump on the other end to determine if it is leaking. If one of those tests fail, then you have your problem. If both seem to go through, then i would start to suspect the alternator.

The only tricky part is that testing the alternator is less than easy, unless you have a multimeter with really long leads. the autozone guys love to rev up their machine to all of 1200 rpm and tell you your alternator is good, but the alternator spends a good deal of time way above that rpm in real life in a honda, so take their test with a grain of salt.

good luck..

 

I don't have a vacuum gauge, so Im not sure about a brake booster leak. As for the battery and alternator, I get 12.3 volts across battery terminals with car not running after sitting over night. With car at idle, I get 14.3 volts across battery terminals, so this would indicate my alternator is ok.

Also I realized the original problem could be due to a low idle since the steering wheel shakes at idle but I measured the idle speed with a tach and got 760 rpm which is correct.

So now I still have the idle dip when I engage anything electrical or put it in gear....and a shaky steering wheel at idle.

 

your battery should be reading 12.65 volts or higher when not is use.

 

sure your alternator might be keeping your battery charged at a idle condition without any load but what is your max load output on it? How many amps is it producing when it needs max output? What is the CCA of your battery while cranking? Just because you see "ok" specs on voltage doesnt mean that your parts are good. Since i'm 100% positive that you dont have the tools to load test either of these components take a day you have mostly free pull your alternator off and go and get it tested at a parts store. Most will/ can do it for free.

 

you can test it without taking it out of the car ... take your car to a local kragen parts or shop to test it but i personally would take it to shop ... there's a tester we use at work called the VAT 45 ... it can test the battery and alternator for you.

 

yes the VAT 45 is EXACTLY what he needs, however most shops arent going to use a few thousand dollar machine on his car for free.

 

Yeah I know its only a crude test I performed, but just trying to get an idea if Im even going down the right path for my original posted problem about the IACV before I pull the alternator for testing.

 

i'd have to look at the specs and a DMM with the part to tell you for sure. Are you sure that you used the right terminals and in the correct direction?

 

Chivid- youre in south san francisco? Im in oakland. The VAT 45 sounds like it could help me...but Im still wondering about my described problem, because the battery/alternator troubleshooting was just one opinion.

 

Yes Im sure. The spec I have in the manual says 8-15 ohms. The reason I even cleaned the IACV and then measured its resistance was because of the idle drop issue I described. Well it was really dirty so no loss there.

 

I mean if you're sure and it's outta specs then it's outta specs....

 

True. But do you think the outta spec IACV could cause the idle to drop for a short period whenever I put the auto tranny in gear or start anything electrical like power windows, locks, ac, etc. Idle also drops the same way when I push the brake in any gear at idle.

The whole battery/alternator testing was in response to a poster who said my problem sounded more like a power issue. He also said to check the booster for leaks which I have not done.

 

well the iacv will cause the idle to bounce around 1500 to 1000 rpm when idling. and when you said you got 1460 ohms if you have multimeter you might had in the wrong range giving you the readings in the thousands when it should be the tenths or hundreds making it 14.60 ohms. get the alternator and battery tested.

 

The out-of-spec low resistance of the IACV indicates that it should be replaced. Consistent with this idea, while the base idle is fine, the IACV is not responding properly to cues from the ECU to increase the idle speed under increased engine load.

Run through all steps in the diagram to verify that the IACV is not working properly.

 

Thanks I will run through the idle speed steps, but the specs I have are a little different.

 

The diagram I posted is for the Si D16A6, so your diagram may be the correct one for the EX D16A6.

 

Alright, I started to run through the idle speed steps. At operating temp, the idle was 760 rpm, then with the IACV disconnected it was 450 rpm, where it should be 650 rpm.

Also I re-measured the resistance across the two pins on the IACV and got 13.5 ohms. Which is now in correct range. Im certain I did not measure the first time incorrectly contrary to a previous post stating I may have had the multimeter on the wrong range setting. You can't go from 14.60 to 1460 by having the multimeter in the wrong range, it doesn't work that way. So my guess is that because I measured the resistance after I cleaned the heck out of it with brake cleaner, it was so cold it showed really high resistance.

So now do I just adjust the idle screw up from 450 to 650 rpm with IACV disconnected? The screw looks like its never been adjusted, it was painted over until I started scraping.

 

FIXED!

 

Correct

 

Alright, will do. But would a seafoam treatment on the intake also raise the idle? The IACV was so dirty Im thinking the intake may be really bad too. I'm just trying to figure out what caused the idle to be low with IACV detached.

 

It's worth a try. Also check whether the PCV valve is clogged.

 

Ok, I adjusted the idle screw with the IACV unplugged to bring the idle up from 450 to 650 rpms. Re-plugged IACV, pulled hazard fuse to reset, then idled car in all conditions listed and the idle checked out just fine from 760 rpm with no load to 775 with High beams and defroster to 810 with AC on high.

I passed everything on this booster leak test:
http://i267.photobucket.com/albums/i...cture_2353.jpg

Pulled the pcv valve it was just fine, not clogged and only allowed air to pass in one direction.

Back to square one, I still have the idle dip issue.