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V6 (1994-2004) Mustangs Technical discussions on the 3.8L and 3.9L V6 torque monsters

Unique misfire problem

Old 04-17-2013, 11:21 PM
  #1  
Levine
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Join Date: Apr 2013
Location: VA
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Default Unique misfire problem

Hello everyone,


I just found this forum because I am so desperate to figure out what is wrong with my 2001 v6 MT.(175k miles)

So here is the story.

Once the weather got better here in Southwest Virginia my mustang started to sputter/jerk/jump/misfire when pushing gas pedal more than it is needed. Sudden flooring at 25mph in the 4th gear would cause the engine to misfire, sputter and behave badly. Same situation with all other gears(except 1st): when going slowly and hitting gas the car would jerk, misfire and sputter. Interestingly, same thing happens during idling. If I hit gas hard the engine momentarily kind of vibrates and misfires. If I gradually press the gas pedal it acts very smooth. The idling itself is very smooth. When accelerating with WOT the car misfires and acts weird till about 3500RPM after that it gets better but not perfect. At about 5000rpm I can hear occasional backfire (not sure where from , sounds more like intake). Overall it seems like the car only acts weird when the gas pedal goes(fast) beyond certain level until that level it is totally fine.

First thing I did I changed fuel filter with 0 results and a lot of gasoline spilled around me.


Check engine light is NOT on (!). However once hooked up to the computer it show cylinder 1 misfire. After replacing wires and plugs it does not show any codes whatsoever.

I tried to disconnect&connect DPFE sensor while the engine was running, the result was two codes: cylinder 1 misfire and high voltage in DPFE.After reseting codes nothing came up again.

Having read a lot of stuff on the forums decided to check if new DPFE would do anything. Tried it with 0 results. Then I took off the coil pack and tested it with multimeter. All the resistance values turned out to be consistent. So coil pack is rulled out.

Then I tried to change the EGR valve itself, which kind of helped to reduce the jerk and sputter. Now under sub 3500rpm acceleration car does not jump/sputter/jerk so violently but the gear shifter still vibrates with vengeance. With windows rolled down I can clearly hear the misfire under the above mentioned conditions.

The local shop guys are waving arms saying they have no clue what is going on because the car "ain't throwing no codes". The shop guys rulled out cam sensor , DPFE sensor and fuel pump and even injectors. They said that it can't be cam sensor or injectors because car would not start and idle so well. It can't be fuel pump because at high rpm the car goes really well. It can't be DPFE sensor because it is not throwing any codes.

The big question is what part is responsible for dealing with inappropriately hard pressed gas pedal and why it can't handle too much throttle anymore ?

Some say it is injectors but could car idle well and start well with bad injectors ?


Guys, you are the only people who can help me here.
Thank you!

PS

I guess I should also post a video...
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Old 04-19-2013, 01:01 AM
  #2  
Levine
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Here is the video I shot today:

Please forgive me the shaky quality. I tried my best to capture the sound. I used expensive gear to shoot this video.
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Old 05-29-2013, 01:14 PM
  #3  
St4ng91
 
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Hey my car is doing the exact same thing wondering if you found a solution?
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Old 05-29-2013, 01:33 PM
  #4  
JC316
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Default

Your shop is making assumptions instead of doing tests. The car can and will run with a bad camshaft position sensor, it just wont run right. My best guess here is going to be the coil, but I would still check the fuel pressure just to be safe.
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Old 05-29-2013, 03:41 PM
  #5  
rbowmar
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To add to the coil comments, Just because the resistance is correct doesn't mean it is generating spark. Checking the fuel pressure is a good test of the whole fuel system. Yes, the fuel injectors can malfunction and still allow the car to start and run.

I hope this is useful.
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Old 05-29-2013, 06:10 PM
  #6  
St4ng91
 
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I was ready to rule out the coil after doing the ohm tests but after rbowmar's comment I decided to go out on a limb and replace it anyways. It seems to have solved my acceleration problem! Thanks!
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Old 05-30-2013, 01:53 AM
  #7  
Daehawk
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Seems to me you are just going into too high a gear at too slow a speed and it bogs down. Thats normal. Speed up. It's the driver.
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Old 05-31-2013, 10:08 AM
  #8  
rbowmar
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Originally Posted by St4ng91 View Post
I was ready to rule out the coil after doing the ohm tests but after rbowmar's comment I decided to go out on a limb and replace it anyways. It seems to have solved my acceleration problem! Thanks!
I am glad you found a fix. It is great when a suggestion solves a problem.
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