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crx
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62 Posts
Discussion Starter #1
Guys I am having a problem trying to figure out my surging idle problem. I am running a zc dohc with a jrsc lht upgrade.
Here are the things I have tried.
New Iacv, tested the wiring also
new tps
new water temp sensor
Bled cooling system numerous times..
Tried another ecu, I am using Chrome
Preformed a smoke test did not find any vacuum leaks.

The strangest thing about this problem is once the car hits 150 degrees it will start surging but after if gets a little warmer the idle gets smoother and the surging stops. Any idea on what going on, this car is driving me nuts.
 

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Premium Member
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5,819 Posts
Do you have the fast idle valve? If so that can be causing the surge.
 

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crx
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62 Posts
Discussion Starter #4
couple of things.

does your your jrsc have the bypass valve? and is it working?

will it idle fine with a stock ecu?

i would guess it to be in your tune i had that issue when i was on chrome as well. never got it fixed till i was on neptune so not sure what caused it for me.
civicdxude
Yes it has a bypass valve, it appears to be working. It still acts funny with the stock ecu but much better. I have heard that chrome can cause idle issues also . I am thinking of upgrading to Hondata or neptune. I really do not like how its idling, just does not seem as smooth as it should be, maybe its the blue dsm injectors(I had them tested and cleaned). I plan on upgrading next year with more boost.

2jzdreamin
no fast idle valve
 

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Meat Popsicle
91 CRX Si
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2,935 Posts
The bypass valve won't affect the idle, even if it is stuck closed. I had a non-working bypass valve in place for years before I realized that it was stuck closed the entire time.

How is the PCV port on the S-tube plumbed? You sure all the vacuum ports on the manifold are either connected or capped? Make sure you double check the 2x ports on the back of the S-tube/supercharger adapter.

I run cleaned and flowed DSM injectors, as did a majority of the people who ran these kits 20 years ago did, and I haven't had any issues.
 

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crx
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62 Posts
Discussion Starter #6
The bypass valve won't affect the idle, even if it is stuck closed. I had a non-working bypass valve in place for years before I realized that it was stuck closed the entire time.

How is the PCV port on the S-tube plumbed? You sure all the vacuum ports on the manifold are either connected or capped? Make sure you double check the 2x ports on the back of the S-tube/supercharger adapter.

I run cleaned and flowed DSM injectors, as did a majority of the people who ran these kits 20 years ago did, and I haven't had any issues.
Pat

PCV on the s-tube is blocked off, I am running a catch can from the black box and valve cover. I completely forgot about those 2 ports, I am sure they are blocked off, I think one runs to the bypass valve? I did run a smoke test on it and could not find any leaks and my smoke machine puts out a lot of smoke.

Thanks for the suggestions
 

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crx
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62 Posts
Discussion Starter #7 (Edited)
Guys I fixed the surging idle, turns out I had a pin hole leak in a coolant hose. Air was getting into the cooling system.

Now I have a weird issue with the car running lean at idle it fluctuates from afr 14.9 to 15.8 at idle and its running a little rough.
 

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Meat Popsicle
91 CRX Si
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2,935 Posts
Hrmm...how was air getting into the coolant?

Anyway, the AFR thing definitely sounds like a tune issue. I would datalog at idle and see what's going on. Is it holding a steady vacuum?
 

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crx
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Discussion Starter #9 (Edited)
Pat I figured the pin hole was causing an air pocket, maybe it was the wrong way to say it. All I know is it stopped since I fixed the leak, lol..

Unfortunately I did not tune it and do not have any experience tuning. I had it dyno tuned at a local shop. The vacuum I believe is steady but a little low, I am running colt tri flow cams and the base idle is set a little high 1000rmps. I will double check to see if if it holds a steady vacuum.
 
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