91 Gt Running Very Rich

Discussion in 'Fox 5.0 Mustang Tech' started by little_redfox_91, Jul 11, 2017.

  1. Could this be what's causing my 91 to miss and run excessively rich. These are capacitors on my ecm board.
     

    Attached Files:

  2. I gotta give it to ya,....You're the first guy that has taken his ECU apart to try and determine why his engine isn't running right.
    (Not inferring in any way that that would've been the first step in troubleshooting a problem)

    The blue one does look to be burned/corroded at it's base, but how is it that you decided to open up your EEC because your engine is running rich,..and how do you know that that IC has anything to do with that part of the engine's operation?

    I think it's safe to say that nobody here is gonna be able to troubleshoot that circuit board by looking at it.

    What about the usual stuff like...Does the car still have it's O2 sensors hooked up/Cats still in place/EGR circuit functioning as a starting point.
     
  3. The cap in the first pic is absolutely bad. :hide:
     
  4. Well considering I've tried a new MAF new o2s new bap sensor and thing has fixed it. I don't know if it has anything to with that's what I'm asking.
     
  5. I'm guessing you have looked for codes, and what mods have you done to it?
     
  6. It doesn't flash the 2 times it should to pull Codes. Long story short been running the same set up for 3 years. Went to start the car as soon as I let off the key it would die, i thought i had the ignition fixed so hook the battery back up and the column started smoking and stuff well I had the spring in the wrong spot so I corrected that issue so after that it's been running like crap
     
  7. so your computer will not go into diagnostic mode? you get no flashing cel light?
    you likely need a computer, or get that one looked at.
     
  8. That first cap does look bad to me as well. Cheap to try and replace them
     
  9. That is an electrolytic capacitor or what is commonly called, a cap. They have a definite life cycle and after 15 or more years, they start to fail. The failure mode is they dry out because the liquid electrolyte leaks out. Then they burn up or blow the top out of the can that they are packaged in. A clue to failure is the top capacitors have a voltage rating, a capacitance rating, a tolerance for the capacitance rating, an operating of the can starts to bulge. When you see one bulging it has either failed or is in the process of Many of the automotive computer repair places will replace all of them as a first step in any repair efforts. The temp rating and a life cycle rating. They also have a specification for cab size and lead placement

    The higher the voltage rating, the larger physical size of the capacitor when compared to one with the same capacitance and a lower voltage rating. Most of the ones used in automotive electronics have a 20-35 volt rating since they are used in low voltage circuits. Using one with a higher voltage rating doesn't hurt anything, but it usually doesn't have any benefits either. There may be a size limitation because of the way the circuit board is laid out. That means there are sometimes limits on replacing the 20 volt cap with a 35 volt cap because it won't physically fit in the space allocated on the circuit board.

    The higher temp rating and longer lifecycle ratings increase the cost of a capacitor. In automotive circuits, those are important factors, and the highest rating stands the best chance of lasting the longest and working the best. Most capacitors used in automotive applications are rated at 105° C The typical capacitor used in most automotive electronics is less than $1.50 each.

    Some informative help from YouTube…

    View: https://www.youtube.com/watch?v=YCSNWi3UHf4


    WWW.digikey.com or www.newark.com are good sources for capacitors, resistors and just about any other quality electronic part. Avoid Radio Shack unless it is a temporary repair or emergency situation. Almost all of their parts are less than top quality stuff and a lot of it is just plain junk.


    That's the easy part now here comes the gotcha... The circuit boards are almost all multilayer construction. That means you have to be able to apply enough heat with a pencil tip soldering tool to melt the solder on at least 4 layers and some times more. Then you need to have a solder sucker to suck up the solder once it turns molten but before it burn or damages the PCB (Printed Circuit Board). I have been fixing PCB's in computers for 38 years now and it is still a challenge to do it right and not make a mess of it.
    The capacitors have a stripe on the side of the can that indicates polarity. Make sure that you match the polarity markings on the capacitor with the polarity markings on the PCB.

    Some more help from YouTube…

    View: https://www.youtube.com/watch?v=urGB_IUXSIM
     
    karthief likes this.
  10. Had the capacitors changed and it runs perfectly again
     
    bfortuna33 and karthief like this.
  11. I am glad that it was that simple, however I still recommend that you dump the codes to find any hidden problems.

    Dump codes sticky

    Look at the top of the 5.0 Tech forum where the sticky threads are posted. One of them is how to dump the computer codes. Codes may be present even if the CEL (Check Engine Light) isn’t on. You don’t need a code reader or scanner – all you need is a paper clip, or if your lady friend has a hair pin, that will do the job.
    I highly suggest that you read it and follow the instructions to dump the codes. http://www.stangnet.com/mustang-forums/threads/how-to-pull-codes-from-eec4.889006/
     
  12. Who did you use to fix it?
    Computer repair guy?
    15 year old hacker?
     
  13. That is definitely bad. I'm getting ready to fix mine today same situation. I got the caps from Amazon for about five bucks total.
     
  14. Did you bother to read my tech note on caps? The two critical items are the temperature rating and operating life. Your Amazon caps probably don't meet either of those specs.

    The higher temp rating and longer lifecycle ratings increase the cost of a capacitor. In automotive circuits, those are important factors, and the highest rating stands the best chance of lasting the longest and working the best. Most capacitors used in automotive applications are rated at 105° C The typical capacitor used in most automotive electronics is less than $1.50 each.
     
  15. Yes I did. The ratings on the caps are identical to the ones that came out. If you know of a better kind or type please let Me know. They are definitely easy enough to change. Thank you.