bouncing rpms
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Joined: Jan 2003
Posts: 139
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From: Pittsburgh, PA
Car: 1990 RS
Engine: 3.1 MPFI
Transmission: 700R4
bouncing rpms
Originally posted by Nixon1
Does sound like vacuum..try listening for it. If you hear a steady HISS noise, it's vacuum. I removed the vacuum line from my manifold going to my cruise control box, and put some elecrical tape over the end on the manifold. When the tape came off, I heard a HISSSSSS when I was driving...but the leak was minor enough that the engine compensated for it by raising rpms...my idle got way quick.
Does sound like vacuum..try listening for it. If you hear a steady HISS noise, it's vacuum. I removed the vacuum line from my manifold going to my cruise control box, and put some elecrical tape over the end on the manifold. When the tape came off, I heard a HISSSSSS when I was driving...but the leak was minor enough that the engine compensated for it by raising rpms...my idle got way quick.
i have been wondering for the longest time what the hell could possibly be the reason for the rpms on my 90 3.1 maro to bounce when idling....it never occured to me that the loud hissing that i hear on the left side of my engine bay (right side if looking in) may the cause for this
thanks for the tip now i have to go check vaccum lines
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