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Thread: 89 3.8 help

  1. #1

    Default 89 3.8 help

    Not a 4 eye, but I'm hoping someone can help . I got a 89 tbird base model from a friend. 98k. It runs and idles rough. But it drives pretty well. It runs very rough, especially when you start it. My friend had changed all the ignition. Except the tfi and pip. When I pulled the plugs, all of them looked richer than they should be. Definitely darker than optimal for fuel injection. The back ds one was almost black. I swapped them out and it runs better. I also checked the line to the fuel pressure regulator. It seemed dry. I also think he changed the o2s, but I'm not sure. A quick compression check shows that all cylinders are equal, near 160 lbs.
    I'm thinking about changing the fp and the injectors. But I don't want to throw money at it, unnecessarily.
    Does anyone have any experience on 3.8s, that can give me some advice. It's a nice car. The rough running engine is really it's only problem.
    Thanks

  2. #2

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    Thanks for moving this to the proper section

  3. #3
    FEP Senior Member
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    Does it burn/consume any oil? Any codes stored in the computer? These things are pretty robust aside from the head gaskets. I don't know if I would throw new injectors at it just yet. Do you notice any difference in how it runs if you pull one plug wire off at a time? I thought that generation of the EEC-IV had the ability to do a KOER cylinder balance test. That would also be easy to do. All you need is a paper clip to do KOEO codes and the KOER tests.

    You can rent a fuel pressure tester from a parts store for free. That will tell you if your fuel pressure it good and if you have a possible leaking/stuck injector.

    Send me some pics of this thing if you have any. I don't see too many MN12 cars up here in Michigan any more.
    '89 XR-7 5 Speed
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    '97 Thunderbird
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  4. #4

    Default

    Did a little more testing.
    It doesn't run much better with the tps unplugged. In fact it tended to die without some throttle input. But if I open the throttle just a hair, with it unplugged, it seems to clean up. But any more and it starts to sputter again
    I tested the voltage at the tps.
    Orange wire-5.12v
    Green .993 with throttle closed.
    I did the sweep test. It seemed to raise and lower in voltage just fine
    So I tested the voltage of the map
    Orange 5.12v
    Blue/white( colors maybe incorrect. Working of my terrible memory)
    2.62v
    Then I swapped the map to an e4 one I had
    Got the same 2.62v
    So I'm thinking both the tps and map are probably working.
    If this is incorrect, then please let me know.
    Any other things I can check?
    This seems like a very simple system, yet something it's obviously wrong.
    Maybe egr?
    Thank you for the help

  5. #5

    Default

    And also, the only code was for a purge solenoid issue.

    The fp was fine. And with the key off, held pressure for 10 minutes at least
    It's possible it burns oil. I have never driven it more than around my neighborhood.

  6. #6
    FEP Senior Member
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    I would try running the KOER tests and see if you get anything. https://sbftech.com/index.php/topic,2471.0.html

    Have you checked for vacuum leaks (hoses, tubes, etc)? It is 30 years old now and although it is better than an 80's carbureted car there are still hoses that can dry out. Especially being down in the southwest.
    '89 XR-7 5 Speed
    '95 SC 5 Speed
    '91 Crown Vic P72 351W
    '97 Thunderbird
    '85 Ford LTD Squire

  7. #7

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    So I ran the cylinder balance test. The engine was warned up.
    The first time I got cylinder 3 and 6
    I ran the test 2 more times and got code 9, system passes.
    So why would 3 and 6 show up in the first test but not in the next 2?

  8. #8
    FEP Senior Member
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    Not sure. You could do an old fashioned cylinder balance test and focus on those cylinders and see if you notice anything.

    I'd still give the potential for a vacuum leak some consideration
    '89 XR-7 5 Speed
    '95 SC 5 Speed
    '91 Crown Vic P72 351W
    '97 Thunderbird
    '85 Ford LTD Squire

  9. #9

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    In this weird time, I decided to buy 6 injectors off rock Auto for $21, because my local place charged $18, and was half way across town.
    But I changed all 6 injectors and the regulator. Fired up and was a bit rough idling. But it drives perfectly!!.
    Later, it had a problem with dying when put in gear.
    But even with that, I have a dirt driveway and I could hang the back end out as I cornered. And even in my neighborhood, it drove great. Almost like a V8!
    Thanks for everyone's advice. It never seemed like injectors were the problem, but it was the only thing left and surprisingly it solved the problem

  10. #10
    FEP Super Member erratic50's Avatar
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    I don't know what years on the birds Ford went throttle body injection vs multi-port speed density vs MAF based EFI.

    I'm curious if it was originally a SpeedDensity that was converted to MAF or if has always been MAF. Also curious if it might happen to have the wrong ECU in it, etc. Has it ever ran properly that you know of?

    I'm thinkng you may want to check for vacuum leaks or an intake gasket failure. Also follow the idle speed reset process and verify base timing and other similar things to see where you're at.

    I smell a rat here. Like maybe the fuel pressure being way too high or a stuck injector, etc. I'm also thinking it will run pig rich at idle if the vacuum line going to the map sensor is not getting vacuum and its a SD setup. There are also problems if they are hooked into vacuum and they are not supposed to be.

    Is the regulator hooked up to the correct vacuum source?

    Did some bone-head so something foolish with the EGR. Or perhaps is the EGR stuck open?

    You did not say if the car has any form of aftermarket cam or if its on boost or anything. Those take us down more paths of troubleshooting of course.

    Good luck with it!

  11. #11
    FEP Supporter Broncojunkie's Avatar
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    Many years ago, I had a car (thunderbuzzard or mustang... can't recall) with 3.8. It was always running rich and fouling out plugs. I finally realized it was running too cool because a previous owner either put a lower-temp t-stat in it, or the spring was just showing signs of wear. Either way, a warmer t-stat fixed the problem.
    79 Pace Car - 331, t5
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  12. #12
    FEP Super Member xctasy's Avatar
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    Yah, the injectors probably just needed cleaning. Purge failure is EGR blockage. After changing injectors, you have to do a nice 80 mike drive to reload updated Keep Alive Memory codes for injector pulsewidth and idle tracking from cold to hot, plus a few hot and cold starts.

    IIRC, 1987 gave us the Port EFi EECiv, and as long as cylinder balance works out with good compressions and the injectors are clean, the KAM will update the tune.

    Every 3.8 from 87 on should have been Port EFi and im pretty sure, MAF sensored.

    The other head tempering, aluminum head corrosion inhibitor verses head studs and gaskets, balance shaft and water in oil issues happen only because the 3.8 port EFi were sold in huge numbers and did long mile yeoman duty.

    It eventually became a great engine; the EECIV fault code reader with long cable is a perfect addition. That balance check was probably showing inconsistant pulse width response at idle,
    withe injector spray pounds per second on one or two going psych at certain points in it delivery.

    Good work!

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