1993 Civic Si - Revving Issues at IDLE
 

Hello Guys\Gals,

Rob here from NC. Happy owner of a 1993 Civic Si HB! I've had this car since high school and it's treated me very well. But it was put on the back burner and sentenced to a life of punishment in the driveway. I now want to get it back on the road and back to fighting form. After checking all fluids and replacing battery she started right up. However, it revvs up and down at idle from regular idle of 1000 rpm's to roughly 2000 just up and down - up and down. I have read some similar posts that say to check coolant level and bleed to ensure no air bubbles i did that with no luck. Next thing to look for will be if the MAF, IAC or FIT sensors are bad. Also after a few light test runs up and down the street i notice my check engine idiot light comes on (possibly when engine gets up to temp?) but then goes off after turned off and restarted. Does anyone know if there is a way to clean or test these parts to see if in fact they are the problem before I just buy new ones? I am trying to save some dough in this resto. ;)

Thanks for all the help,

Rob

Re: 1993 Civic Si - Revving Issues at IDLE
 

Pull the CEL code before you do anything.

Re: 1993 Civic Si - Revving Issues at IDLE
 

Thanks GRUMBLE - I am going to do that this weekend. By the way, I went by a couple of junkyards yesterday. Do you know if those sensors are the same for 92-95 accords and civic that ran the 1.6L? Also, the IAC (Idle Air Control Valve) seems to have some weird bolt in it - almost like its riveted to the throttle body/intake plenum - how might you get that off?

Thanks,

Re: 1993 Civic Si - Revving Issues at IDLE
 

dont replace anything without testing/cleaning them first. The FITV isnt even a sensor, it just a mechanical valve. You can easily find out to clean both the FITV and IAC in the FAQ. Also, as mentioned above, pull the cel FIRST before you fo anything else.

Here's a link to fixing the FITV
https://honda-tech.com/forums/acura-integra-6/%2A%2A%2A-how-%2A%2A%2A-clean-your-fitv-aka-fast-idle-thermo-valve-1564019/

and IACV
https://honda-tech.com/forums/acura-integra-6/%2A%2A%2Ahow-clean%2A%2A%2A-your-iacv-k-idle-air-control-valve-1575913/

remember to always check the FAQ before posting

Re: 1993 Civic Si - Revving Issues at IDLE
 

Sounds like its just a vac leak. As stated dont replace anything yet, check all your vac. lines (being the easiest fix) then move on the the harder fix's.

Re: 1993 Civic Si - Revving Issues at IDLE
 

Thanks dpetro1 and phranky! As I said before my Civic had been sitting a long time before I decided to get her back on the road. Although it was doing the same idling issue before i parked it. When i first heard it I was thinking vacuum leak myself. But then multiple people stated it may be one of those sensors. So far I have bled radiator and cleaned K&N filter which was absolutely filthy but neither has resolved issue but both needed to be done anyways so no harm there. This weekend i am taking car to a buddy at a service station to flush radiator and fill, oil change, top all fluids and grease. He is also going to inspect it for me since that has expired as well as my tags. Last but not least we will hook it up to computer and see what it shows us. The most recent time I drove it the check engine light did not come on at all so maybe it will show past codes. I went to junkyard and bought a new MAP sensor for just a couple of bucks eventhough it was off an older accord im going to give it a shot. I couldnt see how to get the others with out taking the whole throttle body and intake plenum.

dpetro1 - i am going to see how to clean/test those specific components now and thanks again!

phranky - You speak of finding a vacuum leak very confidently - I on the other hand see it as a needle in a hay stack. I have seen various tricks using smoke online. Do you use those methods when finding a leak?

THANKS,

Re: 1993 Civic Si - Revving Issues at IDLE
 

Also after i cleaned out my engine compartment I noticed what seemed to be a small leak in the plastic filler hole of my aluminum? radiator - i may have done this to myself by cleaning the brittle old plastic...I will keep an eye on it to see if it is really a leak or not.

Re: 1993 Civic Si - Revving Issues at IDLE
 

you really should head over to the FAQ section. obd1 hondas dont need to be hooked to a computer. you can check CELs with a paperclip. also, i would not change the map sensor unless you test it and confirrm there is a problem. troubleshoot the problem before replacing parts

Re: 1993 Civic Si - Revving Issues at IDLE
 

How long has it been sitting? I would replace the coolant, motor oil, along with the spark plugs. Make sure all is well before driving it. Letting a car sit in the driveway for a long period of time can take a toll on any car.

Re: 1993 Civic Si - Revving Issues at IDLE
 

Stop replacing parts at random and start taking some of the wise advice given to you in this thread.

And by the way, you won't be hooking your old OBD1 ECU to any computer. That's possible for OBD2 but not OBD1 ECUs.

Re: 1993 Civic Si - Revving Issues at IDLE
 

Thank you everyone! I wasnt able to tackle this over the weekend will try this coming weekend. NVTurbo my car had been sitting for at least a year and a half i checked oil etc i jumped it off and it cranked right up! Over the last weekend i took it to a friend who not only inspected it for me he also changed oil and trans fluid topped off all other fluids. We were going to do a radiator flush but i realized i had a leak from the plastic input hole on my otherwise metal radiator. So it may not be a BIG problem yet i am planning on replacing it. This coming weekend i will get into it again. Dpetro1 I am heading over to the faq's section this evening i am curious to see how you can check CEL code with paperclip. RONJ@HT I havent actually replaced any parts yet but i did go to junk yard to see what the pickins looked like i picked up a MAP sensor just in case plus it was only a couple bucks. I will be posting a video on the progress as i want to show what actually remedied the problem. I plan to do things one at a time to see what actually fixed it then i may clean/refresh all sensors etc cuz ill bet it needs it.

Thanks Again,

Re: 1993 Civic Si - Revving Issues at IDLE
 

I'll assume you picked up the MAP sensor because you plan to replace it, despite the lack of any apparent reason to do so. That's called replacing parts at random. This is a technical forum where you have the opportunity to learn how to troubleshoot rather than use random fix strategies.

Re: 1993 Civic Si - Revving Issues at IDLE
 

I had this issue in my 94 EG Coupe. I cleaned the IACV and that nuked the rev bobbing, but my cold start idle was still too high. Screwing down the plastic bushing in the FITV took care of that. Now car starts just like new revving at 1400-1500 dead cold and simmering down to 800-900 warm idle.
Now I just picked up a 93 EG HB. Love the EGs. I'm fairly new to the tuner hobby and just joined this forum. So far I'm enjoying how easy Honda is to work with. I'm going to keep my coupe pretty stock under the hood, just dress it up a bit. The HB is definitely getting built for Go!

Re: 1993 Civic Si - Revving Issues at IDLE
 

I'm having the same issue with a 1993 Civic. Unfortunately, I won't be able to obtain the CEL codes as this 1993 Civic is a race car (therefore all the important bits are missing). I will certainly let them know that they should check the vacuum lines first (makes sense). What would you suggest as a step 2?

Thanks in advance

Re: 1993 Civic Si - Revving Issues at IDLE
 

Hello All - I am finely back around to working on my Civic. I got my tax returns back so i decided to go ahead and buy the IACV. I replaced it today to find out that it DID NOT remedy the issue. :thud: Someone said earlier in the post not to just buy random parts and replace them. I have learned my lesson. I wanted it to be that part sooo sooo bad cause its a fairly simple fitment. But to my misfortune it seems to NOT be the problem. I am really quite mad this didnt work I am going to try to remove and clean the FITV and see if maybe that helps? If anyone has anymore suggestions please let me know.

Hopeless,

Rob

Re: 1993 Civic Si - Revving Issues at IDLE
 

After you replaced the IACV, did you bleed your coolant system?

Re: 1993 Civic Si - Revving Issues at IDLE
 

-check TPS.

Re: 1993 Civic Si - Revving Issues at IDLE
 

Notaracist ----> No I did not. Is that a must do?

Re: 1993 Civic Si - Revving Issues at IDLE
 

Throttle Position Sensor? I'll check it.

Re: 1993 Civic Si - Revving Issues at IDLE
 

-yes, check the voltage and sweep. pretty sure this will cure the idle bouncing around.

-didn't realize that this was a 2 year issue. :P

Re: 1993 Civic Si - Revving Issues at IDLE
 

I don't drive the car but I want to get it back on the road. My 2009 Nissan Frontier is killing me on GAS! Also I dont have a volt meter or oscilla-whatever and I'd have to look up how to do so (I have been reading thread on here about it actually since you mentioned TPS). Would you also suggest removing and clean FITV?? Thanks

10 days later and all you've done is ignore everyone's input. Do as mentioned before you start pulling and cleaning and replacing more parts. It's not a hard process. Any car that sits for that long or longer is going to need some attention. Especially depending on where you live. Pull the cel codes and post them so the people you asked for help from can help you

Re: 1993 Civic Si - Revving Issues at IDLE
 

-harbor freight gives them away, you'll need one in order to test voltage.

-as for the FITV, waste of time.

Re: 1993 Civic Si - Revving Issues at IDLE
 

Actually, along with checking for vacuum and intake air leaks, cleaning and adjusting the FITV should be at the top of the OP's list.

OP - What CEL codes are currently thrown and repeat after resetting the ECU?

Re: 1993 Civic Si - Revving Issues at IDLE
 

Thanks guys - I really do appreciate the input. I work through the rest of this week so I will be working on car again this weekend. I am no mechanic and never claimed to be - I am a regular guy on a fixed income trying to save some money by doing it myself. So while it may seem like basic stuff to yall, for me it may be a completely different story. Anyways as mentioned before I really do appreciate your input and will give you an update this weekend.