Hyde1

Okay so i had this problem for a while and since i had it i threw on the new spark plugs and it helped for a couple minutes then went back to the rough idle. I changed the fuel filter and nothing. This only happens when the engine is warm. in the morning at a cold start it idles at 1500 rpms and sounds like it starts to back fire and slowly goes down to 1000 rpms. as i drive and it gets warm then the idle goes to 500 rpms. I don't know what is wrong. I also looked at it today and unpluged one of the vacuum hoses connected to the fuel rail and that made the rough idle go away. I then connected it back and the rough idle hit even harder. If i leave the hose disconnected it idles fine but when i drive with it disconnected it makes my car surge(vacuum leak) when i come to a stop but then goes away after 25 seconds. thats only when i have the hose disconnected. when its connected i drive and come to a stop it doesnt surge but it idles rough. Can someone tell me what might cause this?
Pics.



Thats the vacuum hose i was talking about.

EFfin Sedan 91

I would start by cleaning out the IACV, FITV, and replacing the throttle body gasket. That seemed to solve the problem for me. The gasket is ~3 dollars and cleaning the sensors just takes some time and some throttle body/carb cleaner.

mitchh29

That hose is connected to the fuel pressure regulator. Mine is currently disconnected and im planning on fixing that. Im thinking thats whats causing mine to have a low idle. Leave it connected.

Hyde1

I'll try to clean it tomorrow since i have work in a bit. and try a new gasket aswell. Thanks! But for the carb cleaner what would i spray it on? the throttle body? I also replaced the IACV but what kind of valve is a FITV?

Hyde1

Is the problem the fuel pressure regulator then?

_Smartin_

Could also be air in the cooling system if you've messed w that recently. Try burping the system too.

mitchh29

It could be. Ill pm you when i replace mine and Let you know

Hyde1

Well i haven't messed with the cooling system besides refilling the coolant tank. and burping the system? how would i do that?

Hyde1

Okay thanks i appreciate it!

Emeraldbomber

Either fitv or iacv need cleaning. The coolant may need to be bled. Throttle may need cleaning. If that FPR is dieing or bad it will make a crappy idle.

Hyde1

fitv? and i changed the iacv a while ago from a junked civic but it seems like that one was way better then mine anyways. and i might clean the throttle body tomorrow but i figured it is the FPR that needs to be replaced but autozone sells them for around $80 -. - might buy this used one i found on ebay for $20 because it looks a lot cleaner than mine.

Project97EX

I'm sure you have tried this but in case you haven't. Disconnect the IACV adjust the idle screw and reconnect it. That helped my idle. At first i forgot to disconnect the IACV and it didn't really do much.

Hyde1

No i havent tried that! thanks! do you know if theres a diagram or video i could look at to see what im working with? thanks !

Project97EX

This might help. https://honda-tech.com/forums/honda-civic-del-sol-1992-2000-1/adjusting-idle-3041878/

There is another link on adjusting the FITV too https://honda-tech.com/forums/honda-crx-ef-civic-1988-1991-3/how-fix-your-idleing-woes-fitv-iacv-2153910/

hopefully that helps

Emeraldbomber

FITV= Fast Idle Thermal Valve

hmoobvwj

My car was like that and all it took mine lucky was just adjusting the idle screw.

Hyde1

Thanks! this did help a bit but it still idles a little rough :/ so im guessing its the FPR.

Thanks!

Project97EX

Is the Check Engine light on? If so, what codes are coming up?

Hyde1

It was on and it gave the Primary Oxygen Sensor code, i replaced the o2 sensor and that cleared the light. but my rough idle was even before the cel

Hyde1

Bump, still havent found a solution :/ and now my car surges when it starts and last for about a minute then goes away. i think that might be caused by the iacv sensor

Bighun318

yes but did you clean it with carb cleaner???

ERHonda15

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mitchh29

Hey Hyde so when I replaced my fuel pressure regulator it seemed to help exponentially. I had to do some tinkering with another vacuum line to get the idle just right though. Im pretty sure we don't have the same intake Mani though so it might even out for you with just a new fuel pressure regulator hooked up.

Emeraldbomber

Did you reset the ecu?

Hyde1

No i didnt clean it with car cleaner :/ i might be able to clean it today though.

Oh nice! I can buy a fuel pressure regulator online for about $25 but it's used. should i go for it?

Yes i reset the ECU by removing the fuse for 5 min.