85 supra revs at 2000rpm can't figure out why help please!

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  1. #1
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    85 supra revs at 2000rpm can't figure out why help please!

    Hey guys just did my injectors on my 85 supra runs on all 6 cylinders now smoothly except it ides at 2000rpm want one double check my timing but can barely line up the marks think the revs have something to do with it.. Cleaned my idle control valve and still no luck any other suggestions please would be a great help!
    Thanks guys.

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  3. #2
    CelicaSupra.com Member ddd228's Avatar
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    Yes. It needs to be at idle speed to check the timing on the crankshaft.
    I suspect that the IAC went funky and won't idle down OR you have a brand new vacuum leak that you did not anticipate.

    You are supposed to short the yellow connector,but on my '84,it doesn't care.
    Besides,your timing shouldn't change,unless you did sompin' else to upset it. No,really!

    Forget the timing (for now) and find that pesky vacuum leak.
    You had the engine apart!

    Chase that leak and you will be golden. See?

    Find vacuum leak:

    Multiple ways. If the radiator fan is not blowing a hurricane(it will),try carburetor cleaner,but be careful!

    Do NOT shoot a spray at the distributor or the alternator or near the coil/igniter.
    The other way is to use a propane torch HOSE.
    If the idle speeds up,near the vacuum leak,you have found the problem!
    Shoot the intake tract,injector area and the hoses that lead to the throttle body.

    Be sure that a CO 2 fire extinguisher is handy.
    OK,a garden hose.

    I hope this suggestion is helpful.
    Dave in Seattle. I keep LATE hours.Hidden Content
    '84 type "L" ,Auto ,daily driver. Dk blue.

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    So the TPS shouldn't have anything to do with it? Just want to account all factors

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  6. #4
    Founding Member pdupler's Avatar
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    Quote Originally Posted by DougJoseph View Post
    So the TPS shouldn't have anything to do with it? Just want to account all factors
    Yes, TPS tells computer that the throttle is closed, wide open or part way. If the TPS is out of spec, it could be fueling like it thinks you're running down the highway. But often what I've seen with the TPS is that the idle speed will be high, but also it will not be steady, rather going up and down or surging. Did you or someone else take it off the throttle body and put it back on for some reason? At the factory, they dab paint on the screws I assume so that the technicians later can tell at a glance if its been tampered with or come loose. If you didn't mess with it, then look for a vacuum leak first. Always diagnose in the order of simple/least expensive first, progressing towards most complex/expensive last.
    Phil D.
    85 Silver 6m-gte, completed 2000

    "I always observe the speed limit. I see those DAMNED signs everywhere."

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    Quote Originally Posted by pdupler View Post
    Yes, TPS tells computer that the throttle is closed, wide open or part way. If the TPS is out of spec, it could be fueling like it thinks you're running down the highway. But often what I've seen with the TPS is that the idle speed will be high, but also it will not be steady, rather going up and down or surging. Did you or someone else take it off the throttle body and put it back on for some reason? At the factory, they dab paint on the screws I assume so that the technicians later can tell at a glance if its been tampered with or come loose. If you didn't mess with it, then look for a vacuum leak first. Always diagnose in the order of simple/least expensive first, progressing towards most complex/expensive last.
    Well to make the story short I bought the car as is guy said it needs injectors because it was running rough and missing on a few cylinders he's a mechanic so put some trust into him and believed him which so far he was right minus the fact that yes when I first looked at the TPS it was loose with white marker on it as if he might have played with it prior to finding out if it was injectors causing the issue. So yes now I'm stuck as too whether he messed the tps up to much or not as for vacuum leaks what would be the easiest way to check for them on the 5mge? I let it run the other night and sprayed brake clean all over the vacc lines no surge or anything. Also cleaned the idle control valve didn't look that dirty aND don't really know how it works but even after it was cleaned you definitely can't push the spring/plunger down using ać finger at all. Thanks for the help and anything else that can point me in the right direction would be greatly appreciated!

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    Maybe there isn't any vacuum leaks in the usual places, but what about around the injectors? Did you lube the seals when you installed the injectors? It also helps to soak them in gasoline before installation as well. If a top seal is the problem, you'll generally have a fuel leak. But a bottom seal problem could also be a vacuum leak. And it's the area where repairs were just done.
    Another possibility is that the ECU thinks the engine is stone cold and isn't dropping the speed via the ISCM as the engine warms up. This would indicate a problem with the ECU temp sensor or its connection. It's the green one on the thermostat housing to the right of the thermo time switch which enables the cold start injector. This is not the same sensor that drives the temp gauge. That one is in the head a bit behind and above the distributor.
    The TPS should also be checked and adjusted per the TSRM. It's much easier to do with the throttle body off the plenum. So it would be handy to have that gasket before you do this. Take the opportunity to replace the TPS screws with allen head bolts so should it ever need adjusting again, you can easily do it without taking anything apart. I mention this because sometimes it will need to be ever so slightly tweaked to work properly in spite of being adjusted exactly as it should be.
    And it'll need to be properly adjusted to set your timing. If jumping the test connector causes your CEL to blink, you're probably OK. But another test is to slow down in a low gear to close to idle speed. If the engine seems to almost shut off at some point before you get down close to idle and / or if you get bucking under very light throttle that goes away with more throttle, you'll need to adjust its position very slightly until these conditions go away.
    Hope this helps.

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    Quote Originally Posted by ray85p View Post
    Maybe there isn't any vacuum leaks in the usual places, but what about around the injectors? Did you lube the seals when you installed the injectors? It also helps to soak them in gasoline before installation as well. If a top seal is the problem, you'll generally have a fuel leak. But a bottom seal problem could also be a vacuum leak. And it's the area where repairs were just done.
    Another possibility is that the ECU thinks the engine is stone cold and isn't dropping the speed via the ISCM as the engine warms up. This would indicate a problem with the ECU temp sensor or its connection. It's the green one on the thermostat housing to the right of the thermo time switch which enables the cold start injector. This is not the same sensor that drives the temp gauge. That one is in the head a bit behind and above the distributor.
    The TPS should also be checked and adjusted per the TSRM. It's much easier to do with the throttle body off the plenum. So it would be handy to have that gasket before you do this. Take the opportunity to replace the TPS screws with allen head bolts so should it ever need adjusting again, you can easily do it without taking anything apart. I mention this because sometimes it will need to be ever so slightly tweaked to work properly in spite of being adjusted exactly as it should be.
    And it'll need to be properly adjusted to set your timing. If jumping the test connector causes your CEL to blink, you're probably OK. But another test is to slow down in a low gear to close to idle speed. If the engine seems to almost shut off at some point before you get down close to idle and / or if you get bucking under very light throttle that goes away with more throttle, you'll need to adjust its position very slightly until these conditions go away.
    Hope this helps.
    The CEL doesn't blink or do anything when I jump the connector I read somewhere that it's supposed to come on when jumping the connector.. I'm going to recalibrate the tps and check everything as per TSRM then see what happens and yes we soaked injectors in gasoline and lubed them there seated nicely.

  10. #8
    Founding Member pdupler's Avatar
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    Quote Originally Posted by DougJoseph View Post
    WAlso cleaned the idle control valve didn't look that dirty aND don't really know how it works but even after it was cleaned you definitely can't push the spring/plunger down using ać finger at all. Thanks for the help and anything else that can point me in the right direction would be greatly appreciated!
    Its a stepper motor. Basically the plunger is on a sort of a screw and the motor winds it in and out, but in very fine increments. So no, you can't push on it and move it. and even when you put power to a pair of terminals as shown in the TSRM to test, it will only screw or unscrew 1/4 turn which is imperceptible. It takes hundreds of cycles of power, controlled by the computer to move it all the way in or out.
    Phil D.
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  11. #9
    CelicaSupra.com Member supraz's Avatar
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    The Idle Speed Control (ISC) valve just adjusts the size of an air line that bypasses the throttle blade. It runs from the air intake tube that runs over the engine to the ISC valve and then into the air plenum downstream of the throttle blade. If the ISC valve is now stuck in one position it could behave like you describe.

    A quick and dirty way to see if it is the ISC valve rather than an air leak is to simply take a set of pliers and squish down on the black tube running from the air intake to the ISC valve.
    As you start to squeeze it the idle speed should drop. If it doesn't, you probably have an air leak downstream from the throttle body.

    If it does slow down, you have a problem with the ISC valve being stuck, the electronics driving the ISC valve, a sensor that gives information to the ECU to determine what idle speed should be, or a TPS that is misadjusted.

    The idle speed control function of the ECU only works when it thinks that the throttle blade is closed and the engine is idling. It does not adjust idle speed when you are driving and changing throttle position! It senses this with a pair of contacts on the TPS. These contacts are shorted together when you have your foot off the throttle and the throttle stop has not been mis-adjusted by someone trying to adjust the idle speed. You can take the connector off the TPS and measure the resistance of these 2 pins. If they are not shorted, the idle speed will not be adjusted. This would indicate the TPS sensor is bad or the throttle stop adjustment screw is not in the right position.

    Every time you shut your engine off, you will hear a 'little death rattle' which is actually the ISC valve being stepped fully open so that when you start the engine the next time there will be enough air to start the engine. It steps the valve 255 times to ensure that it is fully open no matter where it was before. The valve drive is clutched so it doesn't hurt the valve if it is only half open.

    If you don't hear this sound you probably have an ISC problem.

    Dale
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  12. #10
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    Well I got the revving figured out the gasket between the cold start injector and intake plenum replaced it and was able to get it timed and it runs great although after I took it for the first Drive it started to rev up and down 1000-2000rpm like it was surging now it's back idling at 1800rpm but timing is good and runs good don't know if I should really mess with the idle screw it looks like it's never been touched so I think it's still something else. Confused lol

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