I'm sure this is nothing new here in the forum, but here it goes:

I have a 93 Civic 1.5 automatic that had a bad Vehicle Speed Sensor and I replaced it with one from a Junk Yard.

That problem is taken care of now, but the car's idle-while in park and when cold-will jump up and down from 1200 to about 1700 rpm.

It wasn't doing this before I changed the VSS and I don't see how it would matter.

I did clear the codes by disconnecting the battery cables AND removing the "BACKUP" fuse from the fuse box.

Anyway, I was also getting a code "1" which pointed to a fualty Oxygen Sensor. I bought one from AutoZone (Bosh O.E. replacement) and it threw it in and after driving for about 5 minutes, the Check Engine light came on again. I got on this website and others and discovered that DENSO O2 sensors is the way to go. I returned the BOSCH sensor and ordered a DENSO.

Anyway, could the bad 02 sensor be causing this loopy idle? and if so, why wasn't it doing it before I changed out the VSS?

Can anyone help!?

THanks!

 

i am not exactly sure but dam well could b do to fuel mixture. ur o2 sensor along with the other sensors on what to make ur fuel mixture out to what it is. ecu read the info and the ecu has a mapped ratio air/fuel

 

Thanks for responding...

I don't think it's the air/fuel mixture. I really believe it's a sensor of some sort. It can't be the VSS since I changed that. Could it be the O2 sensor? I've ordered a DENSO replacement but I don't think it would cause the idle to move up and down like that. I

It's just weird how it started happening right after I changed the VSS(Vehicle Speed Sensor). I did remove the IAC valve to clean it and did find some "moisture" on it. I cleaned it off, put it back on, started the car and it ran fine for a while then it came back.

When I run the code check, all I get is the O2 sensor code which will soon be replaced.

Oh, another thing. There are not vacuum leaks that I can see.


Anyone?[&:]

 

well i know if 2 cyclenders get different mixtures it can cause some problem.... i am a motorcycle guy so i will say it like this... when a carb synch is off 1 cylender works harder then another and it is notice able... same could go for a car.

 

jlh,
please let me know if you find out what it is. I am having a similar problem with my 91. It seems to be doing this more when it is warmed up though. It feels like a sensor adjusting or something. When I am coasting the car in gear with my foot off the gas it will make the car go slower and faster. If anybody else knows what I can try, or if there is some sort of sensor that I could try changing?
Thanks

 

I think i'm getting closer. I think I may have a bad Fast Idle Thermo Valve AND a bad Intake Idle Control Valve because today, with the help of this awesome troubleshooting guide that I found on another site, I took apart and tested per the guide two of the sensors and I got it to idle okay, but I can tell it wants to go back to the "hunting" idle.

I hope they don't mind that I give a link to this guide...



Here it is:

http://www.ef-honda.com/ben/Badidle.php


Copy and paste it and check it out. From what I've read it could be one of these valves or a combination of both, in my case.

Try it and let me know.

 

Thanks for the response!! I was just working on my car last night and starting to figure the same thing though I haven't tested it yet. I think mine is just the air idle control valve. I have a few used ones from another engine but don't know if they are good and i need gaskets first before I can try either.
Does anybody know where I can get gaskets for these, and can the control valve be cleaned up to use ok? or is it best to get a new one. I've been searching the internet for this and can find the part 90.00 for a used one, or 150.00 for new, so I thought I would try to stick one of my others on and see if it makes a difference.
Thanks for the link! and hope you got it figured out

 

I just checked out the site, very good!! exactly what I need and interesting.
Thanks again

 

I just checked out the site, very good!! exactly what I need and interesting.
Thanks again

 

Where did you find the IAC valve for 90? I may have to buy a new one.


THanks!