antonio1122

I know its 53728626 thread but I'm lost completely and I need car for work. I have bounce of 100rpm +/- and when pressing clutch it goes even lower then goes back up(not always though, only sometimes). I just recently replaced TPS/IACV with used ones but they worked for past 2 months. TPS has correct voltage. Diagnostics I did are.

Its making this issues ONLY when it warms up, when its cold and not yet reached working temp it idles fine. No vacuum leaks either all hoses are new.

Unplugged TPS - car instantly died
Unplugged MAP - car instantly died
Unplugged IACV - nothing happens, bouncing "may" be a little lower but it still bounces.

Bouncing isnt "quick" bouncing, it slowly goes up and down then its fine for few seconds, then it does it again. Last night it was doing that for 3-4 mins then car just died.

The diagnostic part is what throws me off, why is nothing happening when disconnecting IACV? Although when I plug IACV back I hear high buzzing sound and rev slightly just up then goes back to bouncing. Whole TB and IM were cleaned recently, this started to happen all of the sudden though.

No CEL
DOHC ZC

What should I do? Thank you.

civicservice

What do your fuel trims look like under idle and 3000 rpm?

antonio1122

Its an OBD0 ECU, cant really access that. My biggest question is that buzzing noise from IACV as well as no difference when disconnecting it. Also car runs perfectly fine when cold, when its warm is when issue starts happening, it was all good until 2 days ago.

crazyhorse2011

Go clean your grounds. Battery negative, valve cover ground wire, transmission ground wire, thermostat housing ground wire. Use sandpaper on everything.

antonio1122

I did direct ground from battery to both transmission and body which are fairly new (4 months old) and cleaned every other possible ground. I genuinely doubt ground has anything to do when engine gets warm, however I could be wrong.

Any other ideas why IACV doesnt react the way its supposed to when disconnecting?

crazyhorse2011

Ground has everything to do with the performance of your engine. If your ECU isn't getting solid readings everything gets all fucked up. Go undo the ground wire off the thermostat housing, move your air intake out of the way and reach down there with a 10mm socket and undo the two bolts. Clean the loop connectors and clean the mating surface. Reconnect.

Then go drive around and when your car acts up again pull codes from the ECU

crazyhorse2011

This sounds electrical in nature. Your engine seems to work fine but the ECU is having trouble keeping things steady. When you plug your IACV back in I believe it is supposed to make a buzzing noise because there is a stepper motor inside it that responds to ECU voltage. The idle should raise up a tad when you do this. By unplugging the IACV you put the motor at its base idle setting. If you could please also tell us what the engine is idling at when the IACV is unplugged when warm that would be great. Also tell us what year make model and engine this is....

antonio1122

It makes buzzing noise BUT idle goes tad higher then goes back to where it was all the time and bouncing around 800rpm, which is how much there is before I disconnected it. When I disconnect it while running nothing changes whatosever as if it wasnt even plugged, while both MAP and TPS kill the engine instantly when unplugged.

Its Del Sol 1992, DOHC ZC engine swapped like 2-3 years ago. Thank you for your time!

fragmare

If it's only happening during warmup, check your FITV - Fast Idle Thermo Valve. Sits kind of under and behind your throttle body. Take it out (it's only a couple bolts iirc), take off the little cap end with the tubing neck, clean everything out really well with brake cleaner. Then get a flathead or a cat's paw or something and screw that little white cylinder inside there back down to the bottom of the bore. Blow it all dry, screw it back together, bolt it back onto the throttle body and stick the tubing back on. Start the car COLD and see if the bouncing idle went away. If it did, the FITV cylinder was backed out too far and/or fouled up.

#14 on the diagram here:

antonio1122

I dont have FITV. And this is happening when car reaches operating temperature, I have water gauge and right about when it hits 85c it starts doing all sort of ****. I just cant understand this.

antonio1122

I've just tried with an old IACV I have (it had extremely high cold idle but worked fine when warm), I tried disconnecting cables to reset ECU for 10 mins (not sure if thats even enough tbh) and fired it up, when it got warm is started stalling and doing all sort of this then died. What now? I'll leave cables disconnected overnight just in case I didnt reset ECU properly but I genuinely doubt it will make any difference. I'm completely lost right now. Although fun fact, when I plugged this new IACV and started the car, I immediatelly tried disconnecting it while running and car died, while with the previous one car would just stay running and when re-connecting this one I didnt hear that loud buzz noise. Is it only a matter of resetting ECU right now or I have 2 fucked up IACVs or something else? Thanks everyone for reading this.

crazyhorse2011

Is there air in the cooling system?
Also, have you followed the manufacturer instructions for setting the idle on the car?

crazyhorse2011

You should post up a video dawg

antonio1122

Nope no air, I recently like a month ago changed all coolants and it was running like a champ until yesterday when it started acting up.

Also my cilinder position sensor on exhaust cam had inside oil leak that got into connector however I had that leak for a year lol and it was working, that copper gasket whatever it is that is held by washer, I took it apart and sealed it with victor reinz high temp, I re-used old gasket(just added reinz on it to keep it steady) and its not leaking oil but could that make issues? I doubt it since oil leak in connector didnt and I fixed it just cause I had time. Its just a shaft thats secured with that pivot or whatever you call it(not from english speaking country), pretty straightforward process. I doubt thats an issue otherwise it would cause problems right away ... I dont really know what would video tell you other than my rpms going up/down 100 +/- when car reaches operating temperature (85c). Excuse me if you find my posts rude or offending, I'm just ******* lost and this makes no absolute sense. While it fluctates the charging from alternator doesnt change so its not caused by drop of voltage, drop of voltage wouldnt make sense either cause it goes up then down, not the other way around.

crazyhorse2011

I guarantee you it's something simple. Even if you replaced your vacuum hoses you need to check for air leaks... Take the car in the open and make sure to spray away from your air filter box, and near your intake manifold vacuum hoses and brake booster get a spray bottle of water and mist like a mother****er, I'm talking like you're jerking that bottle off spraying a heavy mist around the engine. Be careful to avoid the air intake box or filter so you don't create a false positive. If you hear the engine stumble up, spray heavier in the area you were just spraying in to confirm there is vacuum leak. It would help if you could actually get the engine to idle at 1 speed and 1 speed only to make this easier to detect.

That sensor probably isn't important, as long as there's no oil on the connectors to mess with the electrical connection it shouldn't be causing this. Also, did you check for engine codes like I stated earlier? I told you to reset your ecu by unplugging the battery for a minute or two and then drive around until the CEL lights up or the car starts acting up again.

antonio1122

Which is exactly what I did, when it started fluctating I checked ECU for codes, none ... It throws me off and leaves me with nothing to work with. I have sprayed whole can of carb cleaner and I have nee intake gasket, tps, TB gasket. It just started all of the sudden.

Its impossible to get it to stay at one speed though however I can tell when theres vacuum leak, it has such steady nice sounding idle while its warming up that you would never believe me when I say it starts heavily fluctate and almost stall when it reaches operating temp. I even tried hitting TPS slightly with a screwdriver, nothing, that rules out TPS I guess? All issues start when it gets to operating temp, just ******* insane.

crazyhorse2011

when you checked for codes did the check engine light stay on solid and not turn off, or did it just turn off and stay off?

crazyhorse2011

Also you said you cleaned all your grounds.

Please confirm with me right now, did you clean the ground on the THERMOSTAT HOUSING by removing the two 10 mm bolts and sanding everything and reconnecting everything together the way it was?

civic402lx

Check for leak using smokes, not from a can of carb cleaner or brame cleaner.
i had a very, very small leak coming from behind the tb clamshell. Smokes reveal that quickly and confirmed the idle issue.

use a smoke machine if you have access to one. Or youtube how to find vac leak using smokes. If its leaking, the smokes will tell u where.

crazyhorse2011

You can also smoke a hookah in your garage, get good and hotboxed in there, then run your car and see where the smoke gets sucked in

antonio1122

Did smoke test, no vacuum leaks as I suspected since everything in brand new, every hose.. I can try and sand off ground at thermo but other than that this **** is crazy, spent last 12h in a garage and I have no idea where to look next.

crazyhorse2011

Okay now im gonna tell you what to do. When you checked for codes did the cel stay lit indefinitely or just turn off?

antonio1122

Its an OBD0, led blinker at ecu is off. If I disconnect IACV it will blink 14 times, already checked that ...

antonio1122

I just got code 9 from ECU, whats that?

It tells its CYP sensor (cylinder n1 sensor) but I've searched and some people say its inside distributor while others say its that thing on exhaust cam. So what is it lol?

My car is OBD0

crazyhorse2011

found this in 15 seconds. Remember, google is your friend
https://honda-tech.com/forums/honda-crx-ef-civic-1988-1991-3/obd0-code-9-cylinder-sensor-need-help-2123528/
looks like it may be that sensor on the exhaust cam by the distributor. Read the link