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Author Topic: Cold idle surge, boost leak?  (Read 657 times)

Offline Ricky Ho

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Cold idle surge, boost leak?
« on: April 28, 2016, 05:15:35 pm »
I'm having cold idle surge issue, and I'm pretty sure I'm idling slightly high (no tach yet due to swap) Still looking for a 90 tach interface if anyones got one!

Once the engine warms up, it doesn't surge while sitting still. If the car starts rolling forward, the idle surges again. I guess the ECU senses the car is moving and idles up slightly.

TPS tested out ok, IACV is ok and tested working. Base timing set at 5deg. BISS screw is screwed all the way in.

My Autometer boost gauge shows its at approx. 17inhg vacuum at idle, and approx. 20inhg when coasting. I tried to do a vacuum leak test with those canned smoke, but I couldn't find anything. All my vacuum ports are plugged except for factory turbo bypass valve, FPR, brake booster and PCV.

Does this sound like a vacumm leak? or a problematic FIAV?

Anyone has a boost leak tester I can borrow or know somewhere I can go to and get one done easily? That should help me locate any vacuum or boost leaks I hope.
I'm still on the stock 14B turbo.


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Offline daniel Dee

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Re: Cold idle surge, boost leak?
« Reply #1 on: April 28, 2016, 10:34:38 pm »
"problematic FIAV?"      check for leaks..or block off

test ISC coils or replace .

http://www.throttlebodys.com/sensors.htm


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Offline Ricky Ho

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Re: Cold idle surge, boost leak?
« Reply #2 on: April 29, 2016, 04:58:23 pm »
Thx Daniel,

I tested the ISC or IACV coil resistance. They were in spec and its an updated "black" model. All tested out to around 40 ish ohms.

I also took it out and turned the key to on position and the ISC did its "homing sequence" like some of the Youtube videos I found. So I would suspect that my ISC is working properly.

Does the vacuum reading sound like I might have a vacuum leak? The intake manifold gaskets are new. And when I did a smoke test I couldn't spot any leaks.
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Offline Brett Haviland

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Re: Cold idle surge, boost leak?
« Reply #3 on: May 30, 2016, 06:15:27 pm »
possible just base idle issues.  You say your BISS is screwed all the way in?  this is not normal.  Have you verified the ECU is getting idle switch signal (on/off),  there is a timing connector, and a obd1 pin connector under the dash, that have to both be grounded when you set the base idle, along with verifying correct timing as well.

I have has this same issue on many many dsm's
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