84 crossfire low vacuum
Thread Starter
2nd Gear
Joined: Sep 2012
Posts: 2
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84 crossfire low vacuum
I just cant figure this out. I only get about 8 pounds of vacuum and my light comes on in the interior that tells me theres an issue. I have checked EVERYTHING and nothing has a leak. I have replaced everything with new parts. Is there something im missing?? The motor is a 350 crossfire electic fuel injection. 
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
Low vacuum isn't necessarily caused by a vacuum leak. In fact, and up to a point, on a CFI, small to medium vacuum leaks (on mine anyway) only caused an increase in idle speed, stable vacuum readings. Anything that causes the engine to run inefficiently will lower manifold vacuum. SO, A/F ratio, timing, Misfiring cylinders, parasitic load...
Draw codes first; if you CEL light came on, you have codes.
Check Timing. If it's overly retarded, you'll have to open the throttles to keep the motor running...low vacuum.
Ensure that all cylinders are firing; good plugs, wires, cap/rotor assy. Compression, valve functioning...
Report back.
Draw codes first; if you CEL light came on, you have codes.
Check Timing. If it's overly retarded, you'll have to open the throttles to keep the motor running...low vacuum.
Ensure that all cylinders are firing; good plugs, wires, cap/rotor assy. Compression, valve functioning...
Report back.
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
And you hooked up a mechanical vacuum gauge to get your 8" reading? Have you checked the vacuum line that runs from the manifold to the MAP sensor for cracks? Look right by the nipples...
What about the other things that I mentioned?
How about some more information: History of the problem, state of the car, etc.?
What about the other things that I mentioned?
How about some more information: History of the problem, state of the car, etc.?
