i have a 93 coupe with a d16z6, it used to have a bouncing idle when it warmed up, now it goes really low like its going to shut off and all lights go dim then the idle comes back up, and it just keeps doing it, back and fourth. Any ideas? (i will try to get a video so u can see and hear it) Any ideas will help alot.

 

i forgot to mention when it used to just bounce i cleaned the FITV and the IACV and put them back on but it didnt do anything. A couple weeks after i did that, it started this.

 

bad alternator? the bouncinfg is either your IACV or a vacuum leak. The low idle could be a bad tps or unplugged. You may check your throttle body for debri in those one of the two holes in side the TB.

 

if it was a bad alternator wouldnt the battery be dead by now? the guy i bought it off of said it had a bad tps sensor, the check engine light is on but i havent thrown the code yet

 

You iacv is bad, thats the reason why it idle really low and bounce up and down. check the code and see if it throws a code 14. At least thats what happen to my engine.

 

how much would one of them be? would one fit off of a 97 coupe ex?

 

would that be the reaon why its idling so low that its almost shutting off and all lights are going dim when it goes that low, then comes backa nd all lights are fine?

 

will one fit off of a 97 coupe ex?

 

your iacv would have nothing to do w dimming lights.. that points to the alternator

 

but the lights only dim when it goes to low idle after the idle comes back up the lights are fine

 

well i think if the rpm's go too low the alternator wont be able to produce the power and they will dim.

 

TPS ftw

 

i know but i still cant figure out why the rpms are goin that low and coming back up to begin with. if it is the IACV will one fit off of a 97 ex coupe?

 

no, the DX one is different I belive.

 

I want to say no... but I'm not sure to be honest.

Replace the FITV with a new one, I really hate those things. You can clean them all you want but once they start to bounce they are almost always trash.

Other than that take some brake clean/water and spray your vac lines to see if you have any small cracks or leaks. This will cause issues.

You can always take the alternator to autozone to see if it's bad, but I have a feeling that's not your problem.

 

I agree that intake air/vacuum leaks and a dirty IACV or faulty/dirty FITV must be considered first. In addition, air trapped in the cooling system can also discombobulate idle control by the IACV and coolant temperature sensor, so you might want to try bleeding the cooling system as detailed in the service manual. A bad coolant temperature sensor is also worth consideration.

 

Forgot about the coolant system. Check your coolant level while you're at it. Could possibly be signs of a blown headgasket, if you get air in the IACV you'll get similar idle issues.

 

I would have guessed alternator... But yeah your battery prolly would be dead as crap by now.

 

nothing is wrong with his alternator. when the idle goes down enough it does not produce enough juice and your headlight will dim. thats a fact. as far as your real issue, it could be many things. ppl get off on saying its the iacv for some reason. that may be your case, but im doubting it. it could be many things. my advice to you is stop pissing with it, take it to a shop that gives free estimates and then you will know what your problem is. then get the part and fix it yourself if you choose. simple.

 

heres my theory, at normal idle, the alternator is running fine, but when the idle goes down, the crank pulley will slow down and since it is also powering the alternator, its causing the lights to dim. The only problem that i have ever encounter of low idle is a bad iacv. if you have a vacumm leak, or any other stuff mention above, the idle would be pretty high, assume that your timing and valves haven't been touch.

From reading your first post, you have a d16z6 and most of the parts are interchangeable with the 97 civic ex that you mention. a new iacv is pretty expensive, retailing around $100 or more at autozone.

Anyways to save you time from trying to figure things out. check the CEL code (recommended) if you don't know how "search", or to dignostic it quick, start your car and let it run for a couple minutes, then located iacv and unplug it. you should notice a difference in idle-ing. if you don't then its your iacv at fault.

Let me know after you have done all that and i'll try my best to help you.

 

ok, the coolant level is fine, but i will try that. does that apply for the o2 sensor also, i was told to try that so i unplugged it and it did change anything?