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Thread: 1986 SVO Mustang Return to Service

  1. #101
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    I am wondering if the O2 sensor is fouled. I do not know how much bearing this sensor has on how a SVO runs, but the symptoms that my car is exhibiting are very similar to what I have been reading happens with a bad O2 sensor. It also seems odd that once the fuel goes into open loop above 3100 rpm it stops having problems. It could be something else, but I should be able to disconnect the O2, put it into open loop and see a change pretty quickly if that is the issue...I think.

    That being said, I am going to pull the codes (assuming that the computer has some) and see if the computer has any knowledge of what is going wrong with it. I dont have high hopes for this working out well since so many things are bypassed/disconnected/etc that it is likely to be a breakfast hash of code goodness, but it is worth a shot.

  2. #102
    Red Captain MikeFleming's Avatar
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    You can disconnect the O2 sensor and it will stay at whatever fuel correction it had last set and will not change from there. If you power-cycle the ECU after that it will set all fuel corrections values back to zero and not move.
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  3. #103
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    Quote Originally Posted by MikeFleming View Post
    You can disconnect the O2 sensor and it will stay at whatever fuel correction it had last set and will not change from there. If you power-cycle the ECU after that it will set all fuel corrections values back to zero and not move.
    I can get behind that. I had been reading up on it on Corral and TurboFord as well, and I see that I need to reset the ECU in order to notice any change. I do believe that reading codes is probably needing to be high on my list of priorities. I am going to hope that this car is better at telling me what is wrong with itself than the system that I work on daily (which is really bad at telling us what is going wrong despite having thousands of trouble codes and sensors).

  4. #104
    Red Captain MikeFleming's Avatar
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    More accurately:

    The ECU starts with no corrections to compensate for air leaks, varying fuel pressure, clogged injectors, etc. Then, using inputs from the O2 sensor, it calculates the amoun t of fuel needed to correct back top zero oxygen in the exhaust (O2 input) and stores that value in KAM (keep alive memory). When the O2 sensor input is missing, it still uses the stored value but no longer corrects it.

    When the ECU looses KAM power, it resets to no correcting. Which, if everything is perfect, will be the exact same place as the previously corrected value. Ther total fuel range of the O2 feedback system is about 1% so it's not much. it's only intended to compensate / correct for small variations in fuel injector calibrations, small differences in fuel pressure, small air leaks, etc.
    Helping SVO owners & racers since 1984

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  5. #105
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    Quote Originally Posted by MikeFleming View Post
    More accurately:

    The ECU starts with no corrections to compensate for air leaks, varying fuel pressure, clogged injectors, etc. Then, using inputs from the O2 sensor, it calculates the amoun t of fuel needed to correct back top zero oxygen in the exhaust (O2 input) and stores that value in KAM (keep alive memory). When the O2 sensor input is missing, it still uses the stored value but no longer corrects it.

    When the ECU looses KAM power, it resets to no correcting. Which, if everything is perfect, will be the exact same place as the previously corrected value. Ther total fuel range of the O2 feedback system is about 1% so it's not much. it's only intended to compensate / correct for small variations in fuel injector calibrations, small differences in fuel pressure, small air leaks, etc.
    I think I have a bigger issue than a 1% variation in some value. Maybe not, but it is lurching pretty good under hard acceleration until the open loop fuel program takes over. I am just going to have to keep doing things until it explodes or gets fixed...I sure hope it doesnt explode...

  6. #106
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    Well, it didnt explode yet. Something is wrong with the diagnostics plug though. I can get the fuel pump to cycle on by grounding one of the wires, but the part that is supposed to read out the codes doesnt do anything. I tried jumpering it with several different implements...2 specifically, a paperclip and a wire with spade connectors on the ends. Neither one did anything of value when the test light was touched to the other connector. I tried scratching at them a bit with the tester to see if I could get a better connection, but there was just nothing there. I dont believe that the car would run without a computer, so the computer must be doing something, but I have no way to tell what that might be.

  7. #107
    Red Captain MikeFleming's Avatar
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    Buy a real EEC-IV tester (AKA OBD-1 Ford tester). They're really cheap now.

    https://www.amazon.com/INNOVA-3145-F...y&sr=8-1-fkmr1

    And don't forget where to lookup codes:

    https://www.svocop.com/Articles/7/index.html
    Helping SVO owners & racers since 1984

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  8. #108
    Building Boost
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    Quote Originally Posted by MikeFleming View Post
    Buy a real EEC-IV tester (AKA OBD-1 Ford tester). They're really cheap now.

    https://www.amazon.com/INNOVA-3145-F...y&sr=8-1-fkmr1

    And don't forget where to lookup codes:

    https://www.svocop.com/Articles/7/index.html
    Yeah, I was going to go to AutoZone and get one on the way home, but there was an accident and I didnt have time. I figured I would be able to pull them with a test light. I will go and pick one up if you think that it will be able to pull the codes when my trusty test light wont...poor test light

  9. #109
    Half Boost rodster's Avatar
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    Just catching up on this thread and I must say I admire your determination! You will concur the beast and will be proud of your accomplishment. Fixing up a car someone has cobbed up is not for the faint of heart. Makes me really appreciate my boring stock 84!

    Carry on!

  10. #110
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    Quote Originally Posted by rodster View Post
    Just catching up on this thread and I must say I admire your determination! You will concur the beast and will be proud of your accomplishment. Fixing up a car someone has cobbed up is not for the faint of heart. Makes me really appreciate my boring stock 84!

    Carry on!
    Thanks. My determination keeps being tested. I keep giving up on this car. Then, I un-give up on it and get back to work. It is all part of my method.

  11. #111
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    And persistence has paid off once again. It is running, driving, boosting...generally doing car things again. Now I can get down to making it better and fixing the messes created by years of negligence and abuse, but at least I do not have to worry about if it will even make it around the block.

  12. #112
    Red Captain MikeFleming's Avatar
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    Quote Originally Posted by brotharon View Post
    And persistence has paid off once again. ... but at least I do not have to worry about if it will even make it around the block.
    So, uhh, what did you do that made it all happy?
    Helping SVO owners & racers since 1984

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  13. #113
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    Oh, that one pump thing that makes the fuel pump have less power. I reconnected it.

    I realized that wasnt very clear. I was in a hurry.
    The is a vacuum operated switch that is zip tied to the wiring harness. This switch causes the fuel pump to get less power unless it detects a load...more or less anyway... I disconnected it because I was informed that I dont need it. Well, maybe I dont need it, but my car sure likes it a lot. I am cure I could probably jumper the wires and bypass it, but I was just trying everything that I could think of, and one of those things was to put back the silly part that I took out and see if that does anything. I didnt expect it to completely fix everything. The car runs very well now. Surprisingly well even. My daughter said it runs pretty good, so that is all I need to know.
    Last edited by brotharon; 10-05-2019 at 04:02 PM.

  14. #114
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    Good for you for not giving up on it! Now you can just enjoy!

  15. #115
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    Now I can start working on the things that are the things that I thought that I would be working on from the onset of the purchase of this car, that is for sure. There is some work that needs done to get it to the condition that I want it to be in. The interior is very tired. There are cracked and faded plastic parts that need restoration/replacement. The driver seat outer bolster is worn through. I am not sure if that can be fixed or if I need to replace it. I did find an SVO steering wheel that is in terrible condition and I am going to restore that and put it into the car so that I can get rid of the ill-fitting Grant steering wheel that is in there now. The SVO shift knob is gone and I will probably be putting a cobra or similar shift knob in to replace it. The heater core needs replaced, and the wiring behind the dash is most likely a rats nest just like under the hood. I will tackle it when I pull the dash to replace the heater core and upper dash pad. I will tackle the rats nest under the hood when I get to the point that I am ready to paint the car since I will likely pull the motor so that I can get inside the engine bay all cleaned up as well...and I will probably smooth out the multitude of bonus holes that were put in for various things over the years.
    I think I will enjoy these things. It will certainly take me a while to get through all of it, and that is ok, but I want to try to keep it running/driving as much as possible through the whole process. Obviously there will be points where it will be down for 30 days or more because of the scope of the repair job, but I just dont want to take it all the way apart and then have it sit for 5 years+ while I think about getting back to it only to find that I dont know where all the parts are or what goes where when I do finally get around to trying to reassemble it...I have experience with this type of project, and do not want to go through it again. It broke my heart to have to sell off a car that I put a lot of work into because I just wasnt able to keep the project rolling along (this was while i was on active duty, and there were 3 deployments in that 5 year span which had a lot to do with the thing failing to be a priority).
    Thanks for all the help and motivation to date. I will keep updating...with or without pictures...as the project moves along. I think that I am making good progress, and I am pleasantly surprised at how easy this car is to work on.

  16. #116
    Building Boost
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    Now that the car runs pretty well...

    Update #1: When the car arrived to me it rode quite rough. I dug in and found that the stock springs had been replaced with Eibach Sportlines. Those are nice springs, but are too aggressive for what I am trying to do. I bought a set of Eibach Pro Kit springs off of a gentleman on SVOCA and have started putting them on. I have the back springs on at this point. There is a reason that I only have the back springs on, and that I started with the back springs.

    This last weekend I went down to my local U-Pull-It yard in search of a nice set of over the axle exhaust pipes. The car came with a single 3" pipe with a welded in resonator. Not only did this take away from the overall appearance of the car (in my opinion), the pipe was very very rusty and looked horrible. I pulled a set of muffler back pipes from a 2000ish GT with some nice polished stainless tips. I got them all fitted up, while I had the suspension out, because I figured it was easier (and maybe necessary) to do it that way. I am waiting on a piece that I need to come in the mail in the next few days so I can weld up my mid pipe to tie it all in to the 3" downpipe. When it is all done I will have 3" downpipe to 2.5 inch in/out mufflers and 2.5" pipes the rest of the way back to 3" stainless tips. Maybe it is not as optimal as 3" pipes all the way back, but for 50 bucks at the wrecking yard (including the hangars which were missing from my car) I give it a thumbs up.

    Since I am waiting on the part I need for the exhaust system, and the cooling fan wasnt working because the module under the dash gave up the ghost, I decided to do some electrical work of my own. I tied into the coolant temp switch on wire to make sure that is working, and it was, so I hooked up a 4-wire relay in place of the module that was under the dash to control the fan. I have it setup so that it comes on if the temp switch triggers it, the AC triggers it, or the little toggle switch that I put in triggers it (figured it was nice to have an override since it can get hot in Houston). I tested it once I got it all wired up, the temp got to about the 'A' in "NORMAL" on the gauge and then the fan kicked on and dropped it down to the "OR" range. I let it cycle like this a few times in the garage and then tested the AC (that didnt work until I jumped the plug under the hood because there currently isnt a compressor under there) and got it working, and finally tested my switch and it worked as expected.

    That is where the car is at right now. I hope to have the exhaust fully installed this weekend and have the interior cabin back to a reasonable volume. Once that is complete I will probably begin working on getting the interior of the car to where I want it to be. Since that is where, as the driver, I will hope to spend the majority of my time (so far it has been elbows deep in the engine compartment) I would like it to be a lot nicer than it is right now.

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