I am looking at an 85 CRX Si. It starts right up, doesn't seem to leak or smoke. But after it reaches operating temp, it hunts for idle.. revs up to 2k.. then down to 500.. up to 2k.. back and forth.. The owner told me it was a common problem with these... was some sensor or something, but didn't know what ones.. I'm pretty handy with cars and such, but i spend most of my time with my turbo subarus and know very little about hodas. Any help would be appreciated.

I had the same prob after i had worked on my 86 civic si....i would start it and the rpms would go up and down...from like 2000 to 1000 back and forth....turned out that all that was wrong was a vacum hose i forgot to connect. so you might want to make sure yours are all connected...and check all the sensor connections also. hope that helps alittle

I am looking at an 85 CRX Si. It starts right up, doesn't seem to leak or smoke. But after it reaches operating temp, it hunts for idle.. revs up to 2k.. then down to 500.. up to 2k.. back and forth.. The owner told me it was a common problem with these... was some sensor or something, but didn't know what ones.. I'm pretty handy with cars and such, but i spend most of my time with my turbo subarus and know very little about hodas. Any help would be appreciated.


I have an 86 Civic Si with fuel injection. Mine does about the same thing, hunts up and down at idle. I checked the computer under the passenger seat. My computer has two LEDs lit up. The first and the fourth. That adds up to a '9'. According to the manual, a code 9 means the Crank Angle Sensor and the CYL sensors need to be checked. This sensor is inside the base of the distributor. You need to disconnect the plug at the distributor and measure the resistance, in Ohms, between the red wire and white wire (should be between .65 and .85 Ohms). Then measure the resistance in Ohms between the brown and blue wire (should be between .65 and .85 Ohms). If the measurements are not as specified, you need to replace the sensors.

Unfortunately, the only way to replace tho$e $en$or$ i$ to replace the distributor. If you buy one from a junkyard, make sure you measure those sensors before you buy the thing.

Good Luck

Thank you both very much for your help. This gives me some great places to begin my search. The Kid that owned the car last replaced all the vacuum lines with some pretty bright yellow ones.. I'm thinking one or more of them are installed incorrectly.

Also, I don't have a manual for the car yet. Does anyone have a link to a page with the ECU error codes and the proper way to read them? I am getting conflicting info from different sites.

Thanks again.

Caleb
87 Subaru TurboWagon
85 CRX Si

Wait! Beofre you do anythign check the EICV. Its a little device on the back of the intake manifold. Make sure its plugged in, and make sure theres coolant going in there. I woudl drain the cool;ant and add new coolant and rebleed the system. Also check all hoses liek mentioned... Coudl be a leak somewhere.

Check for an ECU Code too.
Here is the manual
http://www.redpepperracing.com/technical/87Civ-fsm

hello i am a new member. just acquired an 86 civic si with the exact same problem. fast idle is perfect right around 1900. as soon as the fast idle kicks off, it hunts for the idle. someone told me check the idle air controller too. CASAVARGAS- (not yellin just lettin ya know i'm askin ya a question), are you sure that's not a code 14, i heard at one of the shops i worked at that a code like that might be 1-4 meaning 14. i don't intend this to be ignorant or anything, just asking. the reason i ask is my friends 86 crx had a 2nd and 3rd light and it meant 23(according to someone). well i hope you guys can help. i learned something.

I posted this to the other page, something i learned the hard way, and you have to check up on people if you don't do it yourself. If you replace the )2 sensor and do not solder the wire correctly, you will get ecu error code and bad idle. It's simple, but hard to track down.(at least it was for me)

I posted this to the other page, something i learned the hard way, and you have to check up on people if you don't do it yourself. If you replace the )2 sensor and do not solder the wire correctly, you will get ecu error code and bad idle. It's simple, but hard to track down.(at least it was for me)


Thanks Man,
I hope this solves my problem.

So, what is the right procedure for soldering the 02 sensor?

I dont know the correct way, I'm sorry. I know it is very incorrect just to twist the wires or use those little connectors. Maybe it is just regular solder. I thought (according to a code I thought I had) it was a distributor sensor and it was not. The car was in for a fast idle valve also and they found the O2 sensor wire on wrong. I really stopped doing things on my own cars way back (other than basic tune up).

well you guys were close i guess....
the real problem here lies in the tps or throttle position sensor. it is located on the intakje right behind the throttle body. bad news first. since it is rivoted in at the factory it is a non servicable item. you must replace the entire manifold, and a new electronic temp. control sensor as well. the manifold used at a junkyard is around 200.00 and may or may not have good sensors and throttle body. new pieced together around 300.00. good news now!!!! if you look in between the tbody and the intake you will see 2 seperate sensors with
a couple of wires and lock connectors. facing the firewall kind of on the passenger side or the plug closer to the left hand side. after you locate it with the engine running disconnect the plug. the engine will idle up to around 2000 rpms. with a flathead screwdriver turn the idle screw down to around 700 to 750 rpms which ever is a more even idle base. then take a piece of elecrical tape, go inside the car and put the tape over the big red pgmi light that will now constantly stay on, until you either fix it or the bulb burns out. it won't cause any harm to the engine except you may lose a couple mpgs in wide open throttle conditions. hope this helps ...

Thats the dumbest reply I ever heard. The tps is a tottaly servicable item. You grind slots into the "rivets" you speak of and unscrew them. You calibrate the new tps with a voltmeter
You can replace just the throttle body alone, no need to replace the manifold.

"well you guys were close i guess....
the real problem here lies in the tps or throttle position sensor."

Its a suggestion but you dont know if its a fact unless you own or work on the car.

"facing the firewall kind of on the passenger side or the plug closer to the left hand side. after you locate it with the engine running disconnect the plug. the engine will idle up to around 2000 rpms. with a flathead screwdriver turn the idle screw down to around 700 to 750 rpms which ever is a more even idle base. "

If your talking about disconnecting the IACV, it will lower the idle, and youll have to raise the idle screw sometimes to get the motor to idle. The only thing this will do is prevent a higher cold idle.

I still think its the IACV or idle screw. If the TPS is working, it knows its at 0% throttle, but the motor revs up anywas, once it revs past 2k it shuts off the injectors from the TPS signal, thus the hunting idle. The TPS also tells the ECU when its at 80% or more throttle. It doesnt have much to do with the idle. A hunting idle is usually caused by too high of an idle caused by an air leak somewhere. This coudl be a vacuum leak, idle screw or the IACV. Simple as that.

^ +1 :lol:

But what do you expect from someone who's first post is a response to a 3 year old thread.

My issue is similar. My civic is carburated and I can not get it to stay idling once it is warm. Any ideas?

It starts fine and some days it runs with out dieing. I have adjusted the idle several times and it does not matter.