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Discussion Starter #1
looked in searches and I haven't found quite the same issue. I have a 99 3.8. when the car runs for 20 min or so it sputters/bucks/pops when you try to accelerate. it has new fuel filter, coil pack, wire, plugs. I have run injector cleaner through it. any thoughts? thanks, dan
 

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Check all your vacuum lines and your air intake tube for leaks. Vacuum lines can cause this. Also, my wife's old car ran choppy and turned out to be a huge hole on the bottom side of the air intake tube that was impossible to see without taking it off.
 

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How to check for leaks

I just recently ran through this process.
1) With the engine on run CARB cleaner on all the components under the hood. Keep in mind that this could cause a fire so have a fire extinguisher in hand. You are checking for any idle fluctuation.
2) The first process can also be done with a propane torch.
3) Take it to a shop to get it smoked (Not the technical name) any leak can be found by this method.
 

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Discussion Starter #4
i have a new cai so im good there. ill try the vaccume lines in the am when i get home. the 4 options im thinking now are injectors, fuel pump, maf sensor, or cats. i have no engine light coming on as of now. i even held the gas and let the car buck and sputter for about 30 sec to try to throw a code. im hoping to get this figured out quick and start driving this thing to enjoy it. i just bought the car and it had this issue and a REALLY bad tick/knock. i replaced the motor and still have this issue. mostly all the vaccume lines in there are from the replacement motor. i did have to reuse the old injectors as the replacement motor wouldnt start. i had pulled a plug out and tuned the motor over and had no fuel coming out. my budget is running out so hopefully i can get this figured out without too many more new parts and the wife making me sleep in the mustang.
 

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Then I suggest you get comfortable seats because our buckets are not comfy. No seriously good luck. I think you should find an accredited ( not pepboys et al.) Shop they usually can figure it out and charge you little to nothing for the diagnosis.

Sent from my HTC One using Mustang Evolution mobile app
 

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Do you get a code 12 when running diagnostics? Run this while car is showing its butt, if not replace pcm have repaired a few acting like this with a junkyard pcm.just make sure it match's yours as pcm controls lots of things beside motor
 

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Discussion Starter #7
i havent gotten any dash lights to come on and my code reader isnt showing anything. i even tried keeping my foot in it for about a 1/4 mile making it pop and sputter and still got nothing.
 

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Code 12 should show this is pcm self test if your not getting it either wiring or pcm is your problem.you don't have to have check eng light to have codes.have someone"dealer maybe" check before you lunch another engine.most likely what happened to other one.if have friend with same year car and transmission borrow his pcm. Autozone oreily and advance auto scanners are junk
 

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Discussion Starter #9
so over the last couple days I have tried a couple things, I disconnected the exhaust with no change to eliminate a clogged cat. today I got a fuel pres gauge and found im getting 30 psi. and when I hei the throttle it drops to 26 or so quick and back to 30 where it stays. what should I be getting for fuel pressure? thanks for the answers
 

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Discussion Starter #10
ALL FIXED!!!!!!!! rebuild the fuel pump. the screen was clogged with all kinda of junk. its def a fun car to drive now. cant wait to start adding the fun stuff.
 

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Was just gonna tell you fuel pump you weren't getting enough fuel pressure glad you figured it out enjoy the car

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