Loosing power after 4k rpm when warmed up. Please help?

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  1. #1
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    Loosing power after 4k rpm when warmed up. Please help?

    I just got this 84 Supra and replaced the fuel pump and cleaned out the tank. It was sitting about 10 years in the original owners garage before I picked it up.
    It runs great except for after it's warmed up (about 15 min.). After it hits 4K rpms the engine refuses to rev much past 4K and looses power but never dies and runs normal below 4K. Hopefully someone here can point me in the right direction to get this issue solved.
    It has 150K miles and runs great otherwise. I replaced the plugs and air filter but I'm afraid to just start replacing parts to chase the issue . Thanks so much in advance!

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  3. #2
    CelicaSupra.com Member supraz's Avatar
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    As you suggest, it really sounds like a fuel pressure problem, whether it be caused by a bad fuel pump or plugged fuel filter. There are 2 fuel filters, the extremely large one under the intake manifold and the sock located in the gas tank at the fuel pick up.

    This should throw a Check Engine Code 21 (IIRC).

    I would definitely start by seeing if it is throwing this code or any others and going from there.

    https://www.celicasupra.com/forums/sh...t=#post1042770
    Effect of fuel filter sock plugging.

    Your symptoms sound exactly like what I experienced. My check engine light would come on momentarily until I backed off.

    https://www.celicasupra.com/forums/sh...ck+engine+code
    How to read check engine codes

    Let us know what you find.

    Dale
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  4. #3
    CelicaSupra.com Member
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    There's also little screens on the fuel injectors themselves as a last ditch effort to protect them should any crap get through the others. Think of them this way. The sock is to prevent the pump from sucking up anything big enough to jam it up. Then the main fuel filter should catch most smaller stuff but not necessarily everything that might damage or clog a fuel injector nozzle. That's what their screens are for.
    If you've changed the other two filters and are still having this problem, which as Dale says manifests itself as a code 21, lean O2 reading (due to a lack of fuel), you might want to send your injectors out for a good cleaning. There's a company close to me called WitchHunter Performance as well as others that provide this service. Hope this helps.

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  6. #4
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    When I first did my 2JZ swap I was disappointed that it wouldn't rev past 5000 rpm. I had read on the Forums that the Camry throttle cable (forget year and engine type) was a good replacement which I picked up from the local scrap yard. It turns out that I had gotten and installed the wrong throttle cable and it was slightly too long to fully open up the throttle. Got a new MKIV cable and problem solved so perhaps you might ensure that your problem isn't something simple like a badly adjusted throttle cable.
    Original owner 82 P-Type, 2JZGTE, AEM, Borg Warner EFR turbo,NW leather seats, BBK, Coddington Wheels, Raptor Racing exhaust,Truetrac/3.9, 471 hp/452 Tq @17 p.s.i. with 91 octane pump gas

  7. #5
    Did you solve the problem? I am going through the same thing.

  8. #6
    POTATO Tanya's Avatar
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    Quote Originally Posted by Nathan82 View Post
    Did you solve the problem? I am going through the same thing.
    I don't know about the original poster, but it could be a clogged catalytic converter
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  9. #7
    Hi guys!
    I’m experiencing the same issue with my 1985 Supra!
    Replaced the O2 sensor and the problem still occurs.
    I’m waiting for new fuel pump and filters to be installed, and hopping that this will solve my problem.

  10. #8
    CelicaSupra.com Member supraz's Avatar
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    Quote Originally Posted by fernandosilotto View Post
    Hi guys!
    Im experiencing the same issue with my 1985 Supra!
    Replaced the O2 sensor and the problem still occurs.
    Im waiting for new fuel pump and filters to be installed, and hopping that this will solve my problem.
    Is your car throwing engine codes?
    Black 1983 P Type 5 Spd, Cloth Interior, BBK,HRE 17" Wheels, HKS Exhaust
    White 1984 P Type Auto, Leather Interior, Sunroof, Digital Dash

  11. #9
    CelicaSupra.com Member HansBF109's Avatar
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    Mine was doing this, The anti slosh bucket the pump sits in inside the tank collects any bit of debris in the tank and over time fills up with materiel. As the engine ran, the pickup sock collects the material untill its flow is restricted. After turning off the car the particles kind of fall off, only to be collected again after driving around next time. On mine It would lose power or completely cut out on certain throttle settings over a third throttle usually(occasionally diminishing untill it wouldnt even come off idle) If it was misbehaving like this I could rev it and it sounded like it was on a rpm limiter; Remminicent of a fuel cut defender as an example. It was after a extremely predictable amount of driving time. Even if your tank looks clean I bet the bucket the pump sits has a bunch of rust scale or powdery crud like mine did. Im so sick of it im switching to a 69 mustang 20 gallon tank right now. So far everthing is going pretty well but im not done or at a testing point, and as it is unbaffled I dont want to say its the best thing ever yet. I intend to do a light write up when i'm done in a week or two.

    Barring diferent tanks, definitely when you go to change the pump/ replace the filter in the tank make your best effort to clean out the pump bucket and it's feed tube. If your tank is rusty you can (once it is off the car/empty) put a gallon or two of vinager and a handfull or two smaller type roofing nails like the old ones with the big heads (or maybe bb pellets). leave the tank sitting in the sun and shake it hard(you are scraping with the nails or bbs) every 20 or 30 minutes, rotate it so vinager and then shaking covers on diferent areas. The nails scrape off crud the vinager frees. When you are done spray it with brake clean or shake some diesel in it to prevent flashrusting and remove the vinager from the surface. Now you can do your best to remove all the nails. All the baffles in this tank will make that hard maybe something like bb pellets or ball bearings would be better than the nails. You don't need to fill the whole tank with vinager, and do not wash it out with water as it will flash rust; I made that mistake! Good luck to you!
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