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5.0L (1979-1995) Mustang Technical discussions on 5.0 Liter Mustangs within. This does not include the 5.0 from the 2011 Mustang GT. That information is in the 2005-1011 section.

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Old 07-10-2008, 07:41 PM   #1
campbellsoup24
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Default E303 Cam/bad vacuum and bucking issues.

I have an E303 cam in a GT-40 crate motor from summit. I have a trick flow intake and the car has been tuned by Lidio from Alternative Auto. This is kind of a continuation from another post I had on hear, but now that I have done some troubleshooting I have in narrowed down to a vacuum/cam issue. (I hope) The car idles fine right around 1000rpms and has a great lumpy sound to it. The problem is with the bucking I get at low speeds whenI have the pedal just barely pressed. Give it gas and bring up the rpms and it goes away, push in the clutch or let off the gas and it goes away. Has anyone else had this issue or know how to fix it?

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Mike
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Old 07-10-2008, 07:52 PM   #2
94gtcobra
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Default RE: E303 Cam/bad vacuum and bucking issues.

I have the same problem, i guess that's how it is when you have a cam. Mine goes away after i give it some throttle. If i disconnect the egr on my car this goes away.
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Old 07-10-2008, 07:58 PM   #3
campbellsoup24
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Default RE: E303 Cam/bad vacuum and bucking issues.

I'll have to try that with mine and see if that works for me. Thanks, I'll do that tomorrow and get back on here to give my results.
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Old 07-11-2008, 03:29 AM   #4
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Default RE: E303 Cam/bad vacuum and bucking issues.

Yea i think its just cuz the cam. I also have an E cam and my car does the same thing.
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Old 07-11-2008, 08:50 AM   #5
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Default RE: E303 Cam/bad vacuum and bucking issues.

When I disconnect the EGR should I plug the line? Also will disconnecting the EGR cause any other problems? Thanks.
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Old 07-11-2008, 09:23 AM   #6
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Default RE: E303 Cam/bad vacuum and bucking issues.

Ok, soI disconnected the EGR both the connecter and the tube, I didn't plug the tube that I pulled off of the top of the EGR though. I would have to say there was almost no change, maybe just slightly less bucking at low speeds, very little difference though. I will try to find something to plug the small tube and try it again but I am thinking there might be no change.
The next thing I wanted to do was check the timing, even thoughI have been told it is set rightI still want to find out for myself, plus I want to learn how to do it. What should I be looking at timing wise for this set up?

GT-40 Crate Motor
E-303
Trickflow intake
70mm throttle body
#24 lbs injectors
Headers/H-pipe/2 chamber flowmasters.
Mass air sensor 75mm

Thanks,

Mike
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Old 07-11-2008, 01:08 PM   #7
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Default RE: E303 Cam/bad vacuum and bucking issues.

Hey Cambellsoup....yeah my car does the samething I was pullin out my hair trying to chase down a vac. leak or some faulty sensor etc....its just the way the car drives....if you back down timing to stock it will make a reeeal minimal difference in driveability, but you will be sacraficing some HP...so dont do it...especially if a tuner has set it....that means its right where it "should" be.....
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Old 07-11-2008, 01:22 PM   #8
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Default RE: E303 Cam/bad vacuum and bucking issues.

I have the same problem with the same cam
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Old 07-11-2008, 05:22 PM   #9
Joel5.0
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Default RE: E303 Cam/bad vacuum and bucking issues.

It is not the E-303. I've set E-303, Stg 1, B and X-303 setups (including my junk) that do not have that problem. Suggest to start by actually checking vacuum output from the engine at idle. At 750 rpms in a 302 setup, the engine should output 12"-13" Hg...... anything lower than that = you have a problem in the valve train setup/calibration, spark timing, etc. LUK
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Old 07-11-2008, 06:52 PM   #10
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Default RE: E303 Cam/bad vacuum and bucking issues.

Hey Joel, how would you go about checking something like that Hg's? I never got that into "diagnostics" I know you know whats up in this department?
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Old 07-11-2008, 06:52 PM
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