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Sputtering from Vacuum leak?

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Old 03-26-2012, 01:03 PM   #1
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Default Sputtering from Vacuum leak?

'99 Triton 5.4 After my first (attempted) fix of the infamous rotted rubber elbow leading to the intake manifold (common source of vacuum leak) the car ran great for a couple of months. It appears that this 'fix' (using 3/4" heater hose with a 5/8" elbow stuffed inside) has failed, as the original symptoms have returned. Would love to find the proper elbow to fit the 3/4" nipple on the back of the intake manifold, but it seems that only the 5/8" size is available.

1. Do any of you know of a source for the proper 3/4" 90 included on the PCV hose assembly?
2. Any suggestions regarding how to troubleshoot the vacuum lines to weed out other possible leaks? i.e. are there techniques like temporarily plugging some of the ports or something to see how it changes the symptoms?
3. A tiny yellow hard plastic vacuum hose was found to be broken, Although I thought I'd repaired it (see a trend here?), could this potentially be the cause of the sputtering?
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Old 03-26-2012, 11:46 PM   #2
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My wife has no car. If I don't get this figured out in a day or two, my wife is going to:
1. Kill Me, or
2. Buy a new Lexus on credit
Not sure which is worse. If you guys have any ideas, sure would appreciate your expertise.
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Old 03-27-2012, 12:40 AM   #3
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Spray carb cleaner near the lines to pinpoint the area
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Old 03-27-2012, 01:12 AM   #4
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Like 2000 said, sray carb cleaner around the suspect area and if you hear a change in engine idle, your in the area. Do isolated areas one at a time.
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Old 03-27-2012, 10:51 AM   #5
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Thanks 2000 and Blue - great suggestion. You guys are frickin awesome!
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Old 03-27-2012, 10:55 AM   #6
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no problem man I had to figure out a vacum leak on my dads 97 and thats how I fixed it
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Old 03-27-2012, 11:24 AM   #7
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I did a search on Google, and found one video on a "smoke" test. They close off the air intake, and connect a hose into the IAC line. There could be a leak where the PCV valve meets the valve cover, or worse, on the intake manifold. Mine doesn't sputter, but it does idle 4-500 RPM higher, and my 4.6 just threw a check engine light (I'm getting a code reader, but I'll bet it's P071 - lean mix - due to excess air). Poke around Google for vacuum leak, and there's plenty of shadetree mechanics that posted videos.
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Old 03-28-2012, 02:10 PM   #8
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Thanks Warspite. Another option if the carb cleaner fails to locate the (potential) leak.
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Old 03-29-2012, 01:59 PM   #9
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OK guys, I must be doing something wrong. Got no change in idle from carb cleaner. I actually introduced a leak to see if idle changed when carb cleaner applied.... no change. I'm probably just doing it incorrectly. Any suggestions?

The carb cleaner I'm using is Next Dimension Carb Spray. It contains Toluene, Methanol and Methylene Chloride. Looks like nasty stuff.
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Old 03-29-2012, 03:06 PM   #10
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I'm following the steps on the following link:

http://www.2carpros.com/articles/engine-idles-too-high

My next step is to remove and clean the IAC valve, with throttle body cleaner. Kevin, your stuff sounds like it'd strip paint off metal! Too strong for the IAC valve. Disconnect the electrical connector from the IAC valve, and see if there's any difference in RPM. I only noticed a 50 RPM drop when I did this.
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