Manifold vacuum

Booboo

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1997 GT 4.6l. 120k miles.

Idles and runs pretty well. It is sluggish accelerating. I hooked up Forscan Lite to see if I could find anything that doesn't look right. I found the manifold vac while idling is jumping all over the place. Bouncing up and down constantly. Is this a problem? If so, is it a bad sensor or ???
 

07GtS197

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I don’t think that pid means much of anything. I’ve noticed that before too when logging. I think the ecu infers the manifold vacuum from other pids.

What all did you log? One common issue is a dirty maf. Might not be your problem but if it hasn’t been cleaned in a while it’s due for one.
 
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Booboo

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What all did you log? One common issue is a dirty maf. Might not be your problem but if it hasn’t been cleaned in a while it’s due for one.
Never thought about cleaning a maf sensor. I just thought you replaced them. What do you use to clean them? Do I have to go get some of the special maf sensor cleaner or can you just use something like brake cleaner?
 
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Yes CRC makes an actual Mass Air Flow Sensor Cleaner and the can says just that on it. Personally, I have used brake clean and electronics cleaner before with no problems. To be honest with you I stopped using MAF cleaner years ago. Now I just use brake clean they both do the same job and dry extremely fast.
 

RAU03MACH

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i dont use any brake cleaners on electronics or sensors
it will eat plastic
i will carb cleaners throttle body cleaner electrical contact cleaner mass air flow cleaner
 

cobrajeff96

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Problem with brake clean is that it leaves a residue behind. Acetone would be better, but then you'd have to apply it with a foam Qtip and extremely gently at that. Best bet is to just use the MAF cleaner in the aerosol can.
 
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The best thing to do is find a reputable shop and get them to smoke check it. I worked at a shop and used the smoke machine a ton. I forget how much it cost but it wasn't much and well worth it.
 

96blak54

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Im sorry. Let me explain

Take a good stanky cigar....may as well have some friends around sharing....take one of the vacuum lines and blow smoke into the engine while you all look for smoke excaping somewhere it shouldnt be. This is a redneck smoke machine.
 

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