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B18b idle fluctuations in eg hatch

 
Old 02-21-2019, 03:47 PM
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Default B18b idle fluctuations in eg hatch

1994 civic hatchback with a B18b swap. The idle is fine when its cold and it drives fine. When it warms up, it will idle ok for a few seconds and then the rpms drop and come back up. It idles fine again for a few more seconds and repeats.

I have already tried a good known working iacv and ecu. Itís running on a p75 ecu obd1, no check engine lights. New cap and rotor. New timing belt and timing is correct. Coolant has been bled.
I will attach a video I uploaded on YouTube for you to watch. Thereís some long pauses between idle drops because it doesnít do it all the time. Ive got a couple guesses but Iím open to suggestions on the cause. I did the swap in October 18í but the car has been in storage since November so I havenít really messed with it since then. The vibrations are from my exhaust needing adjusted.

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Old 02-21-2019, 05:56 PM
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Default Re: B18b idle fluctuations in eg hatch

IACV on back of intake manifold....
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Old 02-21-2019, 06:46 PM
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Default Re: B18b idle fluctuations in eg hatch

Originally Posted by NVturbo View Post
IACV on back of intake manifold....
I was hoping that too but Iíve already tried swapping that out and it still does it.

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Old 02-21-2019, 07:05 PM
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Default Re: B18b idle fluctuations in eg hatch

You need to raise your base idle up. If you have too low of a base idle (not using the iacv just idle off the throttle stop) the iacv has allot more work to do. Raise the throttle stop screw up a tiny bit till it will idle at about 800 with the iacv unplugged and it should fix it
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Old 02-22-2019, 06:12 PM
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Default Re: B18b idle fluctuations in eg hatch

Originally Posted by K7-1Ktrevor View Post
You need to raise your base idle up. If you have too low of a base idle (not using the iacv just idle off the throttle stop) the iacv has allot more work to do. Raise the throttle stop screw up a tiny bit till it will idle at about 800 with the iacv unplugged and it should fix it
ill give that a try and see if it helps.
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Old 04-04-2019, 04:10 PM
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Default Re: B18b idle fluctuations in eg hatch

Finally had a chance to get to the garage and adjust idle. Made very fine adjustments and still having same symptoms.

Tried another throttle body with different tps and map sensor. Still has same symptoms.

Im open to any other suggestions. Iíve had a lot of Hondaís and never had this happen before.
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Old 04-05-2019, 05:12 AM
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Default Re: B18b idle fluctuations in eg hatch

Try your ecu in another B18B1 swap or Integra and determine is same issue is present.

Verify fuel pressure at idle and when it dies over. Try another working FPR, replace fuel filter while you are at it, then send your injectors off for flow test/cleaning or replace injectors with known working stock 240cc.

Pressurize the coolant system to check for leaks there as well.
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