90 GT Running rich, backfiring?? Help!

Discussion in 'Fox 5.0 Mustang Tech' started by afiveo, Nov 7, 2009.

  1. blackstangt

    blackstangt Member

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    Before you go spending tons of money on new sensors and gadgets, remember that the car is basically 20 years old. My 90 was having very similar problems.

    1. Buy some electronic parts cleaner and dielectric grease.

    2. Disconnect all of your plugs leading to your sensors, especially the black and white 10-pin connectors at the back of the engine compartment.

    3. Spray all of the contact points liberally with the electronic parts cleaner and let dry.

    4. Fill all of the female contacts with dielectric grease.

    5. Plug everything back in.

    Be careful with the plastic clips, they break pretty easily.
    This is the cheapest way to fix the problem and should be tried before anything else. At minimum, it will make the car run better when fixed and for longer. Essentially a maintenance item.

    Good luck and I hope that's all it is on your car too.:nice:
     
    #41
  2. blackstangt

    blackstangt Member

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    Be careful, the clips break easily, get someone to pull the plugs apart, while you pull the clips outward with a screwdriver or pick tool. It took me about 10 minutes to get mine apart by myself.
     
    #42
  3. afiveo

    afiveo New Member

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    Thanks, I'll do that the first chance I get. Probably Friday or Sat.
     
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  4. afiveo

    afiveo New Member

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    Yes, I used new gaskets. I marked all the lines and their locations so I could re-install everything correctly. I am going to pull the upper again and see if something was missed. Thanks
     
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  5. afiveo

    afiveo New Member

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    Thanks for the tips. This is on my "to do" list this weekend as well.
     
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  6. Strype

    Strype Cuthbert catcher
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    The only times that I have ever had backfiring problems were when my distributor went out and when I tried adjusting my fuel pressure regulator without a gauge. A vacuum loss will cause it too.
     
    #46
  7. afiveo

    afiveo New Member

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    I'm getting 11.7 volts at the O2 sensors on the white wires. My battery is low so I assume why it's not 12V.??

    Why are there jumper connections at my 10 pin connectors at the back of the intake? I'm talking about the between the wiring harness connections. It seems to only extend then 4 inches or so. Is that all they are for? I pulled all 4 of them apart and they look pretty clean. I'm going to spray them down and clean them since I have them apart.

    Upper intake is off again and everything was connected properly and the gaskets looked fine. I'm going to go get some more brake cleaner, a new throttle body gasket and some vacuum line to replace it from the front of the intake to below the airbox. It's looks chaulky and the black comes off on your hands.
     
    #47
  8. afiveo

    afiveo New Member

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    I cleaned the ground and connectors at the back of the block and re-installed. still 11.5 11.7 volts at the O2 connections under the car. What is the solenoid that is attched to the charcoal cannister and has the wire running up to th injector harness? The vacuum lines that run to it are old and brittle. Going to get some new lines now.
     
    #48
  9. afiveo

    afiveo New Member

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    I put everything back together. Also went ahead and put new valve cover gaskets on.

    I cleaned the salt and pepper 10 pins and ran a new vacuum line to the charcoal cannister. I also sprayed all elec connections with cleaner and applied new dielectric grease. I also set the TPS at .96 volts. Spent all f...ing day woking on it and still getting a 41 and 91. Running out of ideas now. WTF? :shrug:
     
    #49
  10. liljoe07

    liljoe07 Active Member

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    Do you still have the Mass Air low voltage code in the KOEO test?
     
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  11. afiveo

    afiveo New Member

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    What code is that? I don't now but I think I have earlier in this post. only 41 91 engine one now.
     
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  12. liljoe07

    liljoe07 Active Member

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    Scratch that........ As it would have shown in the KOER test also.

    Hmmmmm?
     
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  13. liljoe07

    liljoe07 Active Member

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    How are the plugs?

    Whats the fuel pressure?
     
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  14. afiveo

    afiveo New Member

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    The plugs are new, no miles, only trouble shooting. Fuel pressure is unknown. New fuel pump, new fuel filter, new 19 #injectors. How do I check pressure?
     
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  15. liljoe07

    liljoe07 Active Member

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    Posted via Mobile Device

    You can rent a fuel pressure gauge from most auto parts stores. Then they will refund you money upon return.


    What about the O2 harness connector. Have you tried cleaning the connections on it? It may help.
     
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  16. afiveo

    afiveo New Member

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    The fuel pressure reg. is newer. I cleaned the O2 connections under the car with brake cleaner and put new dielectic grease on them too. I am getting 11.5 volts on one and 11.7 on the other.

    If I check the voltage at the computer pins again, should the car be running or just key on. It should be between .2 and .9 volts and change often, correct? before I got like 0.01v and it didn't change.
     
    #56
  17. liljoe07

    liljoe07 Active Member

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    Should be running.
     
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  18. cheese_05_70

    cheese_05_70 New Member

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    Posted via Mobile Device when you check them again hit the throttle and see if you get any change from them
     
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  19. real57vetteguy

    real57vetteguy New Member

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    running rich backfiring

    Hi all, Now I am no expert by any means but for two weeks I have been trouble shooting an issue of my own under the 331 trickflow will not run good thread, the car was running terribly rich at idle, then backfiring it was undriveable, I hauled it to the ford dealer and the computer threw all kind of codes but none of them were the problem after all the trouble shooting, it actually ended up being the ignition module, cleared the running rich and backfiring right up, I Know it doesnt make alot of sense but what he describes sounds exactly what I was going through. What are your thoughts?
     
    #59
  20. real57vetteguy

    real57vetteguy New Member

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    re

    any new feedback?
     
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