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Old 07-16-2011, 11:07 PM   #1
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Default Idle hunting after turbo install on factory ecu

So I finished installing the mechanical parts of my turbo system. It's pretty much a cobbled-together Begi/FM/diy gt2554r system. I thought it would be best to start it up on the stock ecu to check for oil/coolant leaks and any issues that may (DID) pop up. I was then planning to plug in the MS1 and LC1, but didn't get that far!

My problem: The car starts up perfectly and will idle fine. If I hit the gas, it works great. Once I let off, it will hunt 400-1100 rpm for 2-5 cycles and then return to normal. All this is in the driveway, not the street.

Notes:
1. Stock ecu, coils, maf, ecu, etc.
2. Did not touch fuel system at all.
3. Only vacuum line touched was for the charcoal canister solenoid line and that was tee'd for the BOV.
4. Tach works fine.
5. Vacuum/boost gauge reads just like it did before turbo install.

Possible causes that I found by searching!
1. Vacuum leak - I heavily sprayed carb cleaner on all vacuum lines and all connections along the intake from filter to throttle body. Being that carb cleaner is non-combustible, I was expecting a drop in idle speed. The idle never changed.
2. Water temp sensor wire on back of engine - I remember clamping that wire when reinstalling my coils a couple years ago and it caused similar issues. So I check that this time as I did remove the coils for an unrelated repair. The wire was not clamped, thus it did not help my idle issue.
3. Bad IAC valve - I unplugged the valve while idling and initially nothing happened. Then as soon as I rev'd the engine and let off, it immediately died. It did not hunt at all. So I'm reasoning that the IAC valve is working.

What am I missing? I plan to run the MS in a parallel configuration, so I assume that my current idle issue will not disappear by plugging in the MS.
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Old 07-17-2011, 12:27 AM   #2
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Also, bov is plumbed back after the MAF and before the turbo.
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Old 07-17-2011, 11:44 AM   #3
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Case Closed

As with most problems, half-assing is usually to blame. I knew I had to put a check valve inline between the intake manifold and the charcoal canister solenoid. So instead of actually tracing the lines to find that solenoid, I assumed that the first solenoid I saw was for the charcoal canister. Well that solenoid is hooked into the fpr, so my check valve was essentially blocking the manifold readings.

Check valve is removed, and everything is happy now. Now it's time to put the MS in and get it idling and then thrown in the bigger injectors and tune the whole thing.
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Old 07-17-2011, 11:45 AM   #4
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disconnect bov and plug the source to see if it maybe the cause.
edit nvm
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Old 07-17-2011, 11:49 AM   #5
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Tech, if the check valve didn't work, I was going to attack the entire bov circuit as the next likely culprit. Thanks!
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