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Need help with vacuum test *video included*

Masterd

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1993 Explorer Sport
So Ive been tinkering around lately trying to eliminate causes for a misfire / rough running condition at about 2500 rpms, and finally got around to recording a video today and need your guys' help analyzing it. Idle vacuum is about 20-21 inches but the needle flicks ever s slightly at idle, just a slight buzz not a significant movement. However when you rev the motor between 2000 and 2500 the needle starts to flick quite a bit and it runs rough, but above 2500 the needle smoothes out again and it appears to run better. While driving, this presents itself as a knock/thump sound at 2000 to 2500, and as soon as it hit 2600 rpm the power hits out of nowhere. So bascially, less power at low revs and then the power hits out of nowhere above 2600. Heres a video to look at and see if you guys can spot anything out of the ordinary:

Click the image to watch it :)
th_CIMG0217.jpg
 



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Masterd

Well-Known Member
Joined
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Messages
807
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City, State
Upland, CA
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1993 Explorer Sport






Roadrunner777

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94 4x4 Sport 88k
Can you repeat the test while driving? Not so worried about video but can you maybe have the gauge so you can see it while driving and verify it behaves the same way?

Have you done fuel pressure tests?

Actually, I would test the TPS next. It's easy to test if you have an volt/ohm meter. Instructions around here somewhere, sorry, I gotta do something or I would write more about it. I'm just thinking you might have a bad spot on the throttle sensor.
 






Masterd

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Alright these are brake torque tests. You can see that the vacuum gauge bounces a bit more around 2000-2500 under load. Around those rpm you may also be able to hear the rattle noise that the motor makes. Do the vacuum readings under load in gear look low to you??? Thanks!

Click to watch:
th_CIMG0218.jpg
 






Masterd

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1993 Explorer Sport
Bump, once more
 












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