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Discussion Starter #1
i have a prob...my '84 5m is rumbling pretty bad...it starts ok but after a second it starts to shake real bad...when i hit the gas it starts to stop at about 15 to 2000 rpm but does it again when back to idle...my father says it is probally the injectors but im not sure...any help would b great..

thanks,
jay
 

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so it starts fine but can't hold an idle. it runs completely fine higher than 1500 rpm? what exactly happens when it "rumbles"? is it just at a really low engine speed like it's about to stall? if you hit the throttle just a liiiittle bit, is it ok?

if it doesn't die and just kind of idles rough, perhaps it is a clogged injector or fuel filter or something. maybe you could try running some of that injector cleaner in your next tank of gas.

i'm not really familiar with these things, but maybe it is a bad idle speed control valve or maybe even a tps with a bad idle switch. the idle speed control valve is controlled by the computer to control the air mixture at idle. the tps has a switch for when the throttle's closed to tell the computer you're at idle. i'm not exactly sure of easy ways to go about testing the two, but i'm guessing it would make sense to check the tps' switch first. if enough of the tps harness is exposed and you had a voltmeter with nice and pointy leads you could hopefully easily test it-- hook one lead to the blue wire, another to the brown wire, and see if it changes with teh throttle completely closed versus it being a little open.
i think it should be ~5v when the throttle's closed.

if the switch is working... i don't really know how to test the valve. i think it's a stepper motor, if you find power and ground leads. if you can get your hands on a haynes manual i bet they'll describe a good way of testing it.


shiva
 

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What was the last few things done to the car? Have you been working on it or just driving and now it's running bad? I'd check for cracks in the intake and vacuum leaks. Then make sure you are getting good spark and that the plugs are still good. Then I would proly pull out the fuel filter and hook it up with no filter if that makes it run go out and get a new fuel filter.
 

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Discussion Starter #4
well the only that has happend is that i recently ran below a 1/4 tank of gas n my father says the injectors got some shit in them from off the bottom of the tank...jus thought i would get a 2nd opinion...thanks for tha help
 

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Well I'd say replace the fuel fillter as it is proly over due anyway. The filtter will clog before the injectors thats why we use fuel filters.
 

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smell the exhaust. does it smell funny? it sounds like an engine with a possibly stuck open injector or something. sounds extremely rich. it probably isn't a clogged injector. or filter if it was it would run bad all the time. can prolly rule out plugs, wires, distributor. if you press the gas down a tinsy bit i mean like barely down does it go away or only after 1500 it goes away? it may not be reading idle from the tps.

a note on the isc valve. they aren't prone to going out on these cars and if it fast idle's the iscv works fine.

i'd say listen for a hissing sound from the car when it's running but it would have to be a bigassed vacuume leak to make the car run crappy.

you can try finding a leak in the intake piping which could mess you up at idle by running the engine with the afm upside down and no filter and slowly put your hand over it and listen for any hissing from the intake pipe. but that's a little unlikely

Kyle
 

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something similar like that happened to my bros Supra, Did a full tune up and nothing worked, turned out that it was the ECU. His car was more messed up then what it sounds yours is doing tho. it all runs fine now tho.
 
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