Best Place to Hook Up Vacuum Guage
06-29-11, 11:21 PM
#1
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Best Place to Hook Up Vacuum Guage
What's the best place to hook up a vacuum gauge with a T? I've been hooking it up to the pressure regulator. Is that okay? Also what should it read?
At the moment I am having rough idle unless I turn the variable resistor more towards lean. At WOT the RPMs stops at 4k almost sounds like it's hit the limiter. Took off all but the Lower Intake and checked that everything was okay...and I saw no problems except a ground issue which I fixed (made no difference).
Thanks,
Richard
At the moment I am having rough idle unless I turn the variable resistor more towards lean. At WOT the RPMs stops at 4k almost sounds like it's hit the limiter. Took off all but the Lower Intake and checked that everything was okay...and I saw no problems except a ground issue which I fixed (made no difference).
Thanks,
Richard
06-30-11, 10:55 AM
#3
Need more info about the car you're talking about. Year/engine/mods/etc...
From your mention of the variable resistor, I'm guessing S4. A pressure regulator will be connected to a vacuum source, so that is an acceptable location to tap into with a vacuum gauge.
The variable resistor will typically need to be somewhere in the middle of its range for a smooth idle. If you're going all the way lean, it could be a sign of an injector dumping fuel into the engine or high fuel pressure, etc... But if it doesn't take much adjustment, it's probably fine.
In any of the threads that I've seen pop up with similar issues, the problem always turned out to be an injector or 2. A bad/dirty injector, a loose injector clip, a loose wire, or just a really bad connection can all cause a major lean hesitation higher in the RPM range. If at part throttle, the other injectors can usually pick up the slack enough to keep the engine running reasonably smooth. The mixture will still be more lean than it should be, but you have to get up into the 16-17 AFR range before you'll get large hesitations.
From your mention of the variable resistor, I'm guessing S4. A pressure regulator will be connected to a vacuum source, so that is an acceptable location to tap into with a vacuum gauge.
The variable resistor will typically need to be somewhere in the middle of its range for a smooth idle. If you're going all the way lean, it could be a sign of an injector dumping fuel into the engine or high fuel pressure, etc... But if it doesn't take much adjustment, it's probably fine.
In any of the threads that I've seen pop up with similar issues, the problem always turned out to be an injector or 2. A bad/dirty injector, a loose injector clip, a loose wire, or just a really bad connection can all cause a major lean hesitation higher in the RPM range. If at part throttle, the other injectors can usually pick up the slack enough to keep the engine running reasonably smooth. The mixture will still be more lean than it should be, but you have to get up into the 16-17 AFR range before you'll get large hesitations.
06-30-11, 11:12 AM
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Yeah its an 86 S4 N/A sorry! Checking the vacuum tonight. Thanks for the advice 
I'll search tonight for some threads on weather (and how) I should clean my injectors, or if I should just replace them. Any links or advice would be appreciated, but if not, I'm sure I can use the search button 
thanks guys!
I'll search tonight for some threads on weather (and how) I should clean my injectors, or if I should just replace them. Any links or advice would be appreciated, but if not, I'm sure I can use the search button thanks guys!
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