4g61t.org

hey guys! im having some car troubles
so, every so often while driving, my 1990 mitsu mirage vl has been cutting out on me while driving. it will start normal, drive normal, then after ~15 miles, the revs will drop to 1, even with the foot pedal depressed/pumping the gas.
thought it was bad gas- so I put; heet in, octane boost, and injector/carb cleaner into the gas after topping it off with 93 octane gas. worked for 2 days then did it again. thought it was the cap and rotor... got new ones and worked for day and a half. thought it was vapor lock, so i got a new gas cap. again, worked for a day or so. Im at a loss . Any help is appreciated
viedos below are whats happening

http://www.youtube.com/watch?v=QjNOxTxX ... NACmP6fyE=

http://www.youtube.com/watch?v=AniFLH0y ... e=youtu.be

p.s. my exhaust is broken at the flex pipe if your wondering why it sounds like... awesomeness!

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1990 Mitsubishi Mirage 4g15
1992 Toyota Corolla All-Trac Wagon
1950 Farmall H Tractor

also, the exhaust smells gas-ey.
could it be that the coil is going bad?

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1990 Mitsubishi Mirage 4g15
1992 Toyota Corolla All-Trac Wagon
1950 Farmall H Tractor

It's ignition related, but that's all I can tell by just watching a video.

Could be an intermittent shorted/open wire, cam sensor, ignition coil, power transistor, or the computer. Not nesesarilly in that order. You need to do some testing with a lab scope.

Another thing I was just thinking is how much it sounds like launch control. Scrap the ignition idea, I think your fuel injectors are cutting on and off erraticly. Check power at the injectors, and check all ECU grounds.

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"A good day racing is better than a great day fishing!"

Didn't watch the video but grab another ecu, one that is known to be good. If that's not it, it never hurts to have a spare. But I'm betting the ecu is the problem. Is the check engine light on? Does it come on when you switch the key on?

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93 Mitsubishi Expo LRV 1.8/manual
95 Eagle Summit DL Coupe 1.5/manual
01 Mitsubishi Mirage ES Sedan 1.8/manual

All this ECU talk scares me. I've swapped my ECU for the 4G37 one, but I feel as if I need to get a backup lol

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1991 Dodge Colt - 1.5L 4G15 - Swap Project
1989 Dodge Colt GT - 2.0 4G63T - Racecar
1995 Honda Prelude - H23A2 - DD

got a new water temp sensor, that didnt fix it, but improved it.
it seems that after it warms up (~15 min) it does the "launch controll sound" where it stops at 1 rev. after replacing the sensor, however, i can work the gas pedal and get it into the higher revs just fine. it is also backfiring (rally car pop pop pop) like i am getting enough gas but no spark. the check engine light comes on with the key, but goes off once I start it.
could it be the Throttle Position Sensor?

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1990 Mitsubishi Mirage 4g15
1992 Toyota Corolla All-Trac Wagon
1950 Farmall H Tractor

out of all the things it could be, ecu is the most likely for almost any scenario short of a flat tire. A "known good" spare ECU is a must when you have a CSM.

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4g61t.com

so my dad thought it was the Oxygen sensor, so we cleaned the (ground?) on the header, and cleaned the sensor itself. proceeded to test drive it for 10 miles, broke down (same thing). we think that once it gets to a certain temperature a code flips? And there is no CEL on. I waited 1 hour for it to cool down, and drove home like nothing was wrong.
I just Swapped the ECU from an 89 sedan VL, but am not so sure that will do the trick
Should I order the O2 sensor?

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1990 Mitsubishi Mirage 4g15
1992 Toyota Corolla All-Trac Wagon
1950 Farmall H Tractor

left it running while i posted last, walked out and found it dead. turned the key and it did the "launch control" thing.
Im going to go ahead and order the O2 sensor

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1990 Mitsubishi Mirage 4g15
1992 Toyota Corolla All-Trac Wagon
1950 Farmall H Tractor

Check that ECU for leaky caps or burnt spots on the board. Not saying that's the problem....just didn't see you mention that you checked it out. If there's a problem with the ECU, it won't exactly tell you, so it's time for visual inspection.

I've had a blast with ECUs. There was one time when I had to use one to start my car and let warm up, then swap in another so I could drive the darned thing.

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Good stuff - trucks bring it!

So, I think I got it! I was thinking that a valve was either stuck on or off because it would only do it when it was warmed up, and possibly using a differnet fuel map(?) so my dad went ahead and checked the PCV(?) valve, and sure enough, after taking it out and cleaning it, my car ran like a champ! I drove it all over, trying to make it sputter, and to my relief, that never happened.

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1990 Mitsubishi Mirage 4g15
1992 Toyota Corolla All-Trac Wagon
1950 Farmall H Tractor

never mind because it is still acting up. Im at a loss here. everything ecu related checks out fine. I might just have to bight the bullet and take it to a shop

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1990 Mitsubishi Mirage 4g15
1992 Toyota Corolla All-Trac Wagon
1950 Farmall H Tractor

checked the ECU and nothing looked wrong. checked the grounds and nothing is wrong.

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1990 Mitsubishi Mirage 4g15
1992 Toyota Corolla All-Trac Wagon
1950 Farmall H Tractor

My best idea is to ditch all the electrics and fit a carb. You never know where you are with 20 year old electronics and it is impossible to measure them yourself in the street. At least with a carb you only have a couple of screws to twiddle with and you can see exactly what's going on.

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http://www.facebook.com/ukspecproton

Cleaning a pcv doesn't usually help on these cars, you should be able to blow through one end and not the other, I bet it leaks but still wont be the cause of your issue.

Also the ECU can "look" perfectly fine and still be bad, that would be my first guess.

Just noticed this thread is a bit old, did you find the issue by now?

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89 Mirage Billet 20g 63t 12.4@120 417whp 400wtq @ English Racing.
89 Colt GT E316g
06 Silverado SS
07 ZX6R