Need advice on frustrating idle issue.

Ok, so.

Basically, when I pull to a halt and my engine rpms drop to idle (1000RPM, tuned) the engine will start to hunt/surge. it moves up to 1500, then steadily down to 1000, then up to 1500 and so on so forth a fair few times before finally settling somewhere between 1000 and 1200.

The amount of times it will hunt before settling varies from twice to like 13 times, sometimes more. and it does not hunt on cold start unless i touch the throttle.

This problem began after I changed the following things on the engine all at once:

Gearbox
Exedy 9.5lb Flywheel
Exedy Stage 1 Clutch
Skunk2 Intake Manifold
Injen CAI
PCV Valve
Hondata IM Gasket

Things I've tried to fix the issue:

-Going over all the vacuum lines/injectors/manifold/brake booster/throttle/charcoal canister with carby cleaner and found no vacuum leaks.

-Reset the ECU.

-Cleaned out the IACV very thoroughly with carby cleaner.

-Cleaned out the FITV very thoroughly with carby cleaner and wound it all the way back in.

-Cleaned the throttle body very thoroughly with carby cleaner.

All I can think of now is air trapped in the cooling system somewhere tricky, faulty PCV valve (even though it's a new one it's not OEM), or is there any way that these parts could mess with the tuning?

The car is a '95 DC2 B18C2 OBD1 w/ Hondata S300.

Are any of these things more common then not? Has anyone else had this issue?

Any and all input is very welcome.

Could it be a ground in the electrics?


I've had cars in teh past surge and hunt because of a ground issue.

that's possible, but I'm pretty damn certain that I got every ground wire back in place when I reassembled everything. so should I just look for a loose wire in a hidden place??

check the ground contacts are clean (maybe give them a light sand?) and nice and tight, see how you go after that.

Does it only happen during the first 10 minutes of the first start up of the day?

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Originally Posted by dorikin

Does it only happen during the first 10 minutes of the first start up of the day?

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nah happens all the time

so ground wires are one thing to check, any other possibilities you guys can think of?

Clear the glue off the idle bleed bypass screw & wind in.
If this fails, log onto ECU via usb & turn idle speed motor response down.
Or come past next time your in Syd & ill sort it out for you.

Ahh thank you!

I will give these a shot and let you know how it goes. I need to learn about using my hondata software, as I've never used it :/

I'm rebuilding the engine head when I finish receiveing all the parts, mostly supertech package. once thats done I'll be making a beeline to your workshop again for another tune.

Adrian, by idle speed motor response do you mean the IAC Duty Cycle?

also I'm thinking of removing the FITV, making a block off plate and gasket and bypassing the coolant lines. or just bypass the lines when I get my 68mm throttle body, as I believe it has no FITV mounting point.

this shouldn't be a problem as the hondata S300 unit controls the cold start idle speed based on coolant temp, correct?

also, just checked the TPS voltage. 0.48 at closed throttle and 4.6 at wide open throttle. so it's a little bit higher then 4.5 at WOT but spot on at closed, so i doubt it'd affect the idle at all. I will calibrate WOT when I get my new thottle body in a week or two.

looking now, as far as I can see all the grounds look good, just to give feedback on everyones early suggestions. and I belched the rest of the air out of the cooling system, ran it till the fans came on twice and quite a few big air bubbles came up, but it still appears to hunt at idle.

FIXED! Plugged into the S300 ECU from laptop and step by step reduced the IAC duty cycle until it smoothed out. took me a bit to figure out how to use the software but I'm happy I got it sorted. :)

the IACDC was quite high with the tuning that was set for my stock intake manifold so I ended up dropiing it about 3 steps to suit the skunk2 manifold.

thanks everyone for the tips.

Glad you got it worked out :)

man , i have the exact issue!!!!!!! btw im the guy who bought your steering wheel lol. did you get this fixed?

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Originally Posted by maaaaark

man , i have the exact issue!!!!!!! btw im the guy who bought your steering wheel lol. did you get this fixed?

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Originally Posted by Super-DA9

FIXED! Plugged into the S300 ECU from laptop and step by step reduced the IAC duty cycle until it smoothed out. took me a bit to figure out how to use the software but I'm happy I got it sorted. :)

the IACDC was quite high with the tuning that was set for my stock intake manifold so I ended up dropiing it about 3 steps to suit the skunk2 manifold.

thanks everyone for the tips.

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http://static.fjcdn.com/pictures/Wat...90_4143719.jpg

Wow talk about back from the dead haha.

Sorry mocchi pic doesn't work? Did I really say I-ACDC??

http://www.licklibrary.com/Images/Re...g_nc%20(1).jpg

did you get your car fixed?

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Originally Posted by cbauto

did you get your car fixed?

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Haha, hi "cbauto" :P

Do you mean the idle issue? Yes a long time ago.

nice.

pm me if you need automotive service

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Originally Posted by cbauto

nice.

pm me if you need automotive service

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Thanks cbauto. I was told by "reliable forum members" that you are the best in town :thumbsup:

Will definitely PM you for oil change soon.