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Unread 03-05-2012   #1 (permalink)
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Default 1996 Mustang V6 engine shaking and rough idling ! Injectors next?

Im new to the forum. Hopefully I can get some help and help someone along the way. Recent owner of a Mustang. I recently bought a 1996 Mustang V6 that needs a little bit of work (great deal, so it's worth it). Engine is shaking when idling so I have checked the ignition coil, spark plugs, spark plugs cables, AIC valve, MAF sensor, ECU, EGR valve and soneloid and still shakes. I pulled spark plug wire cylinder 4 and car immediately stops shaking. That was the reason why I checked the iginition coil and sp cables (I've had that problem before with other cars). So my last guess is that that I have a cyl 4 bad fuel injector. Am I on the right path?

I'm running a scan and ECU is throwing me codes P0171 (system running too lean) and P0136 (O2 circuit). No misfires mentioned. Help!
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Unread 03-05-2012   #2 (permalink)
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So what happens when the #4 fuel injector is disconnected?

Are you positive the plug wires are wired to the correct coil pack holes? I'm having trouble understand why disconnecting a spark plug wire would make the motor run better unless there was a base engine problem.

Check out post #8:
http://www.allfordmustangs.com/forum...ang-3-8-a.html

If you think there's a fuel injector problem, consider an injector cleaning/flow test service such as InjectorRX.com. Once cleaned and tested they are as good as new. Cheaper than new.

It may be helpful to know the results of a compression test.
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Unread 03-05-2012   #3 (permalink)
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Thanks for your response! Im almost sure that wires are connected to the right coil holes. Passenger side, cyl 1,2,3, upper coil pack holes 1, 2, 3. Driver's side, cylinder 4, 5, 6, lower coil pack holes from right to left, 4, 6, 5. Is this right?
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Unread 03-06-2012   #4 (permalink)
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Quote:
Originally Posted by Free Wild Horse View Post
Thanks for your response! Im almost sure that wires are connected to the right coil holes. Passenger side, cyl 1,2,3, upper coil pack holes 1, 2, 3. Driver's side, cylinder 4, 5, 6, lower coil pack holes from right to left, 4, 6, 5. Is this right?
no.. the coil pack is numbered 564
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Unread 03-06-2012   #5 (permalink)
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Default V6 coil pack diagram

Houston.....we have a problem.....

Coil, Cylinder pair
#1, 1-5
#2, 2-6
#3, 3-4

For those of you that need a picture.
Attached Thumbnails
1996 Mustang V6 engine shaking and rough idling ! Injectors next?-v6-coil-pack.gif  
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Unread 03-06-2012   #6 (permalink)
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Quote:
Originally Posted by wmburns View Post
Houston.....we have a problem.....

Coil, Cylinder pair
#1, 1-5
#2, 2-6
#3, 3-4

For those of you that need a picture.


That's how wires are set up. Well, I will disconnect fuel injector cyl 4 and see what happens. If idling improves after doing so, is the fuel injector definitely going bad?

I will check for vacuum leaks too. Any ideas where to start?

What are the main reasons that cause an engine to run lean?

I have been chasing the problem for over a week and I feel Im very close to figure that out. Thanks!
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Unread 03-06-2012   #7 (permalink)
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Quote:
Originally Posted by Free Wild Horse View Post

What are the main reasons that cause an engine to run lean?
  • Unmetered air entering after the MAF.
  • Outside air entering the exhaust before the upstream O2 sensors. The outside air makes the O2 sensors "think" the motor is running lean when it's not. The usual place that a V6 gets an exhaust leak is on the right side manifold. It leaks due to the AC water dripping on the hot manifold. Since the P0171 specifically calls out the right side (bank 1), this is a great place to start looking.
  • Dirty MAF
  • Clogged fuel injectors.
  • Low fuel pressure.
As for how to find vacuum leaks, honestly if you could invent an easy way to find a vacuum leak, you could be famous. But until then:
  • Visual inspection
  • Smoke test
  • Propane base vacuum leak detector. Search Amazon for "vacuum leak detector".
  • Carb/choke cleaner.
For a low tech smoke test:
http://www.allfordmustangs.com/forum...ml#post2942011

I have never been a fan of spraying carb/choke cleaner all over the outside of a modern car. Why? The harsh cleaner may damage the gaskets thus trading one problem for another.
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Unread 03-14-2012   #8 (permalink)
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Quote:
Originally Posted by wmburns View Post
  • Unmetered air entering after the MAF.
  • Outside air entering the exhaust before the upstream O2 sensors. The outside air makes the O2 sensors "think" the motor is running lean when it's not. The usual place that a V6 gets an exhaust leak is on the right side manifold. It leaks due to the AC water dripping on the hot manifold. Since the P0171 specifically calls out the right side (bank 1), this is a great place to start looking.
  • Dirty MAF
  • Clogged fuel injectors.
  • Low fuel pressure.
As for how to find vacuum leaks, honestly if you could invent an easy way to find a vacuum leak, you could be famous. But until then:
  • Visual inspection
  • Smoke test
  • Propane base vacuum leak detector. Search Amazon for "vacuum leak detector".
  • Carb/choke cleaner.
For a low tech smoke test:
http://www.allfordmustangs.com/forum...ml#post2942011

I have never been a fan of spraying carb/choke cleaner all over the outside of a modern car. Why? The harsh cleaner may damage the gaskets thus trading one problem for another.

UPDATE*** I unplugged the cyl 4 injector as you suggested (I had to remove the intake manifold in order to do this) and idling improved. I checked the fuel injector resistance and I got 40 ohms (?) and I compared it to the other fuel injectors (also 40 ohms). So if I'm right, injector itself is still good; it might be clogged so I will take it to a shop to have it professionally cleaned. I will do all of them now that Im at it. On the right track? Thanks!
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Unread 07-17-2013   #9 (permalink)
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Here is someone else with a possibly similar problem, and their fix was a PCM:
http://www.allfordmustangs.com/forum...ang-3-8-a.html
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injector, lean, misfire, oxygen sensor, rough idle



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