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Discussion Starter · #1 ·
Hi im new to the forum and I just picked up a 94 3000gt sl for my little brother. it's his first car so I want it running perfect. My problem is I start the car It will idle at around 1400rpm-1500rpm and then after 2 to 3 minutes it will drop the idle too 400-500 and then die out with no cel.. In that time before it dies I'll try and hit the gas to see if that helps but it feels unresponsive. the car will fire right back up every time but continue to have the same problem. I replaced the iac and the tps but still no changes. if I unplug the maf it will idle but then die out as it should. Could it be the MFI? When I turn the key and start I don't hear any clicking coming from the MIF. I know i should pressure test but I'm having a hard time finding the adapter. any help is greatly appreciated!!!!
 

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Discussion Starter · #3 ·
yes for the first 2 to 3 minutes it's on I can rev it I can pull off in 1st gear or if I need to reverse but as soon as it dies down to 400-500 rpm the throttle doesn't respond.
 

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So there's a couple easy things i would try first. The throttle cable can be tightened to increase the idle speed. Its just on top and behind the intake plenum. It would be cool if it was just loose from sitting.

Another small possibility to help diagnose would be the AC compressor. Turning the ac on makes the car idle higher, probably to account for the increased resistance. You can also unhook the belt and check that all of your accessories are not seized which brings my next thought.

Alternator? I like to unhook the battery after starting the car to check the alternator. The mitsubishi is a little picky. It really prefers 14.4 volts to 12.

Happy hunting, and keep checking back. There are some really experienced guys here who will weigh in if you cant figure it out. Good luck
 

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Discussion Starter · #5 ·
when I turn the wheel I can hear the idle kick in but doesn't kill it. I turn the ac on same thing all good until it gets the 2 or 3 minute mark and the car dies out. its like clockwork haha annoying as hell. I just want to be able to find the problem between you guys and myself. I honestly don't want to take it to the shop really don't trust any near me. I really appreciate the help Tactix!!! all others greatly appreciated as well!!
 

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Is from left field but ....how long the car get not running?? Read 2 or 3 topic about water stuck in baffle in fuel tanks...will try to find the links
 

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A topic by ninjaperformance
 

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Discussion Starter · #8 ·
the guy before me said he would drive it every day until it started doing this. just toghtened the grounds tried it again stays running but same thing. idle gets really low now but runs until I hit the gas
 

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Clogged up fuel filter could cause those symptoms, fuel pressure builds in fuel rails during cranking and then after engine starts (requiring more fuel) restricted fuel flow thru filter causes fuel flow and pressure to slowly drop until there’s not enough at fuel rail to keep engine running.

You could just replace fuel filter and take a chance that’s it, which wouldn’t be bad idea anyway if you don’t know if it’s been changed recently or ever. Or you could install a fuel rail pressure gauge like pictured below and monitor fuel pressure after engine has ran for a minute or two for pressure drop.

I personally like the one from Ninja Performance, but I hear they're having shipping problems lately because of owners health issues (single person type operation).

 

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Discussion Starter · #10 ·
so if I bought the one from 3sx I'd just hook that up and crank it then see what it's at when it's running and right before it shuts off ?
 

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Would try the filter before if i was you for save some $$$ you need to do it anyway .

But yes plug it and watch what happen on the gauge when she stop.
 

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Discussion Starter · #12 ·
sounds good I'm going to grab a new fuel filter on my way home from work tomorrow and see if it changes anything then I'll update back here. thanks so much white93gt and qcstealth92 for the help!!
 

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Can't hurt to pull the ECU for inspection as well. They are known to go back and give weird performance/behavior issues like this.

Ex. when I had a bad ECU, one coil pack would not fire, cleaned it up and cold starts would be fine, but warm/hot starts it would misfire for 10 min, then drive normal again. Ended up replacing it and all my issues went away.
 

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Discussion Starter · #14 ·
I'll have to try that in the meantime while I'm waiting for the fuel filter every auto zone I went to had the filter but somehow no lock nut washers. 🤔 I really appreciate the help!! I'll update back here as soon as I get a chance to pull the ecu.
 

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Discussion Starter · #17 ·
the iac is brand new along with the tps. fuel filter didn't work. still having the same problem
 

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Discussion Starter · #18 ·
it will start up fine will jump to 2 k then drop to 1500 after 2 minutes it'll just drop rpm to 400 idle for alittle ill hit the gas and it will die out
 

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it will start up fine will jump to 2 k then drop to 1500 after 2 minutes it'll just drop rpm to 400 idle for alittle ill hit the gas and it will die out
You pull your ECU out yet to inspect the capacitators?
 

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Discussion Starter · #20 ·
yes they look OK. im trying to get another one that's good to swap it with just to make sure. it feels like someone cuts the fuel...electric..? idk that's the closest thing I can describe it to. I know it's getting fuel from the pump to the filter because the crush washers there gave me with the new filter didn't fit they were too small and car wouldn't start fuel was leaking. I bought 2 new ones and problem solved but still the same problem from the start.
 
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