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Discussion Starter · #1 ·
I purchased a 2013 ST1 back in January of this year(2020). I’ve been chasing a few issues since I bought it. Car was purchased mostly stock minus wing risers and a CPE stage 2 RMM, and Cobb SSM delete. Also, has 2 catch cans installed by first owner.
No intake, no exhaust. No AP.

Car has a pretty rough cold idle, and does it intermittently when warm as well. Feels like misfires and sounds like misfires from the exhaust. Car also will almost stall on me sometimes when coming to a stop and then shoot the idle back up to around 1300RPM. That one is very intermittent, and I can’t replicate it unless it wants to do it.

Things I have replaced/done;

•Spark Plugs

- car came with one step colder NGK 6510s

-replaced with OEM heat range 6509s gapped @ .031. They were dry carbon fouled under 1000 miles. Ground strap was flaking and white indicating lean condition.

- Replaced with one step colder again as recommended by Strat(IIRC) for stock tune gapped @.026 to leave took for gap to widen. Slightly wet looking carbon fouling and still white ground strap.

• Replaced purge line on top of motor. Recall had been done but the solenoid was vibrating like crazy.

•Compression Test was done; all cylinders were @ 150psi on a semi-cold motor. Have yet to do a leak down.

•Full can of seafoam has been ran through intake track

•LTFT is sitting around 11% and STFT was less than 1% might have been 0%, which further confirms lean condition.

Any ideas, help, or wizardry is acceptable. Please help

(Mods I’m sorry if this is in the wrong place, I’m still trying to figure out how forums work?
 

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Test for vacuum leaks.
 

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Discussion Starter · #3 ·
Test for vacuum leaks.
Any spots prone to leakage to start with?? I didn’t think these cars had a MAF so I hadn’t checked that yet....but that wouldn’t explain the intermittent near stall or the issue getting better when the engine is a full temp. Would it?
 

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Re: the rough idle intermittently smoothing out as it warms up - if you have a small vacuum leak the rubber (or whatever material) could be expanding slightly as it heats to close the hole.

Even physical movement could be closing up the hole as the hose gets jostled around.

I’d smoke test the air intake system. If you don’t find any leaks, I’d begin testing the fuel injection system to ensure they are spraying properly.
 

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Discussion Starter · #5 ·
You know what, I’m willing to bet it’s probably from the catch can lines or something stupid simple
 
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