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Thread: New owner of '89 SC 5-speed - problems and concerns

  1. #1
    Join Date
    Mar 2004
    Posts
    34

    New owner of '89 SC 5-speed - problems and concerns

    Hi everyone.

    I just picked up an '89 SC 5-speed. Car is bone stock, has 140,000 miles. I took it for a test drive and it seemed to be OK, although I didn't get a chance to really "get on it".

    Anyway, on the way home, I noticed that the car is dog slow.. like as fast as my '88 Delta 88 with a 3.8. The boost gauge is showing 4 PSI. I thought these cars were supposed to do 10 psi or so? Also, once the car hits 4,000rpms it just completely falls on its face.. I mean, it keeps reving, but the power just DISAPPEARS. What's going on here?

    Another thing - when on the freeway doing 70+ MPH, while I'm on the throttle even a little bit, but even worse at WOT, there is a bad shuttering that the car does. It seems like it might be clutch related, but I'm not sure - as it only does it under acceleration, in any gear.

    I can give more details if you need them.. please help guys! Please tell me I didn't waste $2400 :/

  2. #2
    Join Date
    Jun 2002
    Location
    Illinois
    Posts
    1,744
    Hello, and welcome. I don't think you wasted 2400, especially if the car is cosmetically sound.

    It sounds like you have a few issues, but they all could be pretty simple as the small things can do big things. First, check for vacuum leaks. If your only producing 4psi, this is very likely why. It will slow you down, cut your gas mileage, give rough idle, run rich, and more. Next, you might want to check plugs/wires. They could be pretty old, and could cause the shuttering you notice at freeway speeds.

    How does your trans shift? Syncros ok? Just curious.

    Some other things you should check: Coolant, oil, for maintainance & contamination with each other. Headgaskets can be a problem on these when not maintained, and even after so many miles if they are original. Next, look at your motor mounts. If the mounts are stock, they are fluid filled. The stock hydralic mounts collapse and tear with time, leaving your engine lower than it should be. This cuases the oil pan to rub, the power steering lines to rub, idle problems, and more. They need to be fixed if they are bad, as the oil pan can eventually crack.

    Thats all the major stuff for now, should get you started. Also check out the FAQ & Lit on the main page for significant information about these cars.

    Hope I could help, and enjoy your new SC!

  3. #3
    Join Date
    Nov 2003
    Location
    Rhode Island
    Posts
    667
    Sounds like it could also be a vibration damper problem. If yours is original check it closely for torn rubber in between the parts as these fail all the time on these cars. Check to see if the bolt holding it on hasn't walked out too. It would be a good idea to replace it if it looks original with those miles before it strands you somewhere. You may have a slipping clutch too. Also check your supercharger belt for stretching and cracks, it could be slipping causing your boost problems.

  4. #4
    Join Date
    Mar 2004
    Posts
    122
    I think the previous suggestions were good, especailly regarding the low possible causes for the low peak boost pressure.

    Since the shuttering/shaking problem is most pronounced on acceleration or under power, the motor mounts are a good bet. I've had this problem, althouigh not on the T-Bird, and it behaved similar to what you say.

    About possible clutch problems, when you said that once the car hits 4K RPM that it goes flat but keeps revving, do you mean the car pretty much stops accelerating but the tach keeps climbing right up to 5K or so at the same rate? If so, this would indicate that you have a slipping clutch.

    Or are you saying that it will continue to climb above 4K, but only very slowly? This would probably be caused by the low boost.

    I hope this helps.

  5. #5
    Join Date
    Mar 2004
    Posts
    34
    Quote Originally Posted by jpetillo
    About possible clutch problems, when you said that once the car hits 4K RPM that it goes flat but keeps revving, do you mean the car pretty much stops accelerating but the tach keeps climbing right up to 5K or so at the same rate? If so, this would indicate that you have a slipping clutch.

    Or are you saying that it will continue to climb above 4K, but only very slowly? This would probably be caused by the low boost.
    The car hits about 4300 RPM and then just STOPS there, car doesn't accelerate at all and RPMs don't increase

  6. #6
    Join Date
    Jun 2002
    Location
    Illinois
    Posts
    1,744
    They don't increase at all? Check your oil pressure! We have hydralic lifters which are fed from the oil lubrications system. In the event of a loss of pressure or low oil, these could potentially cause symptoms similar to this.

  7. #7
    Join Date
    Mar 2004
    Posts
    122
    Quote Originally Posted by Digitalchaos
    They don't increase at all? Check your oil pressure! We have hydralic lifters which are fed from the oil lubrications system. In the event of a loss of pressure or low oil, these could potentially cause symptoms similar to this.
    Digitalchaos, would you think that this would also cause a lot of valvetrain noise? I know it would be pretty dramatic in an old chevy engine. But, I've never heard one of these engines under those conditions.

    It's an interesting problem with the low boost.

    11psi5.0, it sounds like your clutch slipping isn't the cause. Does it also not rev over 4300 in 1st gear, too, or just on one of the upper gears? I'd also consider a bad fuel pump, fuel filter, or one of your coils going bad at higher RPMs.

  8. #8
    Join Date
    Mar 2004
    Posts
    34
    Guess what guys..

    After popping the hood and looking over some things, I noticed that the nuts for the flange on the intercooler piping connection right at the top of the intercooler had completely FALLEN OFF. I went out to a hardware store and picked up the right nuts (8mm), tightened it down.. and now the car sees 13psi, and pulls right up to redline with NO problems.


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