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1G Car keeps randomly dying on cold start!!!

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Red_EcliPzE_GsX

20+ Year Contributor
124
42
Nov 25, 2002
Irving, Texas
Guys, I am so lost and frustrated at the issue I’ve been having with the car for a good while now.

90 gsx 5 speed non eprom ecu. It will just completely die on a cold start when it seems to be chilly/cold outside.

I’m not talking sputter and die I mean it straight cuts off like if I turned the ignition off. I don’t know what the hell it could be.

Symptoms:
-first noticed when weather was colder, and only on cold starts
-soon as it got to normal operating temp it would stop doing it
-on normal warm days it would not die at all on cold starts.
-when it dies I lose my check engine light, but if I turn the ignition off/on again it comes back.
-even trying to keep it at a steady higher rev, it will just straight cut off on me as well.
-buddy told me to try unplugging the coolant sensor switch on a cold start to see if it would turn on, to confirm if my coolant sensor switch was bad? I unplugged it, and the car did not want to start at all, it would just sputter really bad. Plugged the sensor back in and then it would turn right on for me, but then of course cut off and die like it does.

As time has gone on though, it seems to have gotten worse.
-it now will do it even when it first gets to operating temp and I attempt to drive off for the first time, literally just dies while I’m in gear going
-just now even after it seemed to finally be acting right long after being at operating temp, just pulling into my complex it just died.

Things I’ve checked:
-my PTU has been replaced with a 91+ when I first noticed I was getting no check engine light with key in on position. I just spliced the wires to work.
-sent ecu off to ecmlink, they said it tested fine but the caps looked like they had been replaced before but could have done a better job, so they replaced caps, tested fine afterwards and even put it in a test car and ecu still fine.
-I’ve done basic things like check plugs, I regapped plugs and have some new ngk wires on the way tomorrow. However I don’t think that is going to help.

here is a video so you can see for yourself. This is about the 15th time of me turning it on again you can see on the temp gauge that it’s still on the colder side(I had just tried turning it on again after it sitting for a few hours from the last time I drove it)

you can hear how it just cuts off completely, wait til end of video and you can see how it’ll even happen if I try to hold a steady rev, and then you can see the check engine light lose its shit.

As I watch the video I notice it seems to die immediately as I hear this click sound?? Not sure where it’s coming from. I know it sounds like I hear it in the car but not sure from where.

I don’t know what else to do!!

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*sigh*

update guys,

so let’s see picking up on this thread again, my issue with the random shut off/no cel on ignition no start.

after replacing the mpi relay and SWEARING that fixed the issue, it didn’t. Sure enough after a few weeks. I started getting a no cel on ignition again and thus no start.

Even though I had the ecu tested/caps replaced on the original ecu that came with the car, I went ahead and got a replacement good working 90 turbo 5 speed eprom ecu.

soon as I went to plug it in, cel came right back on ignition, car fires right up. It ran the best it’s ever ran into that test drive. Turned it on/off several times and everything seemed fine again....


That is until two weeks after that. I go to crank the car on, fires right up of course, but now it misfires a lot more, and will get a TERRIBLE idle where it almost dies.

I just can’t win. The car ran just fine the first day I plugged in the new ecu, and now this!

reading up on here I figured I’d test my ISC maybe it went bad and maybe it fried the drivers on my new ecu.

put a multimeter to the pins on the isc, all reading 30 all fine. Open up the ecu and it still looks flawless drivers show no visible issue.

I attached a video so you can see/hear how it idles and sounds fine for the most part despite some misfiring, but then just immediately goes to a shit idle.

any ideas?? I’m just don’t know what to check now considering everything that’s been replaced so far that I listed at the beginning of this thread


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well for one that screech is the alternator belt or power steering belt, its either tight or not tight enough could be the cause of battery not charging properly! (may still charge but not properly)

that idle drop is horrendous check the fuel pump / fuel filter / fpr may be failing to feed enough gas after it burns whats in the fuel lines seems like it goes super lean and bogs down hard
 
You obviously had multiple problems. First a bad MPI relay, then a bad ECU (no CEL at key on). Now bad idle. Your last video sounds more to me like a lack of fuel pressure than it does a misfire. Perhaps the fuel pressure regulator (FPR) is leaking or dirty fuel filter or fuel pump starting to crap out (maybe even its internal check valve clogged). Can you put a fuel pressure tester on the fuel rail to watch when this bad idle starts? Maybe first just replace the FPR since they are so cheap and it's probably leaking somewhat anyway being so old.
 
Yup seems like fueling issue to me too. I’d check the O2 sensor first though. Check resistance across the two white wires on the sensor for the heating element. It’s a round connector under the thermostat housing.
 
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I have an aftermarket aero motive fpr when I rebuilt the fuel system running all AN ss lines feed/return and a new walbro. And AN lines on both sides of rail, but still using stock fuel filter.

I know the fuel pressure reading on the fpr reads stock pressure 37-38.

but that’s a good idea I’ll check what the fuel pressure reads once that sudden drop in idle happens.

As far as the squeaky belt goes yeah I’ve been lazy to get that sorted but figured that was the least of my problems right now.
 
A bit of an aside, but this is one of those times were ecmlink is sooo valuable and can save so much time and headache. You look at the log and it's like "oh, my wideband goes super lean when this happens" or "my map sensor goes to zero" etc. In my amateur opinion, it seems like fuel pressure too. That belt fix is super easy and takes 5 minutes.
 
Went to fire car up, idles fine and sounds fine on cold start, revs fine, fuel pressure at 38 the whole time. Once it gets to operating temp and the idle just suddenly drops low and starts idling really rough, fuel pressure will increase slightly to 40, but that’s about it. Fuel pressure does not drop at all.

tried unplugging the isc, no change.

I’m stumped as to why it doesn’t begin to rough idle until operating temp.
 
Went to fire car up, idles fine and sounds fine on cold start, revs fine, fuel pressure at 38 the whole time. Once it gets to operating temp and the idle just suddenly drops low and starts idling really rough, fuel pressure will increase slightly to 40, but that’s about it. Fuel pressure does not drop at all.

tried unplugging the isc, no change.

I’m stumped as to why it doesn’t begin to rough idle until operating temp.

for one stock fuel pressure on a 1g and early 2ga 4g63 FPR is 46psi not 37psi on 2gb RS its 50psi
 
yep and mines a manual. Sorry if I never clarified that in this thread.

So you have afpr and stock fpr? Any reason why you didn’t remove the stocker? You set the base fuel pressure with the vacuum hose disconnected and fully warmed up?
 
I have an aero motive afpr with gauge which is how I know what fuel pressure I’m at. It has the vacuum line attached to it currently.

the stock fpr was removed as I replaced all fuel lines with SS AN lines.

It’s BEEN on this same setup, and ran fine all this time. Sure I was having the no cel/no start issue, but base fuel pressure was never messed with this whole time nor were any of the lines or the afpr.

At this point I’m just going to try swapping back in the original ecu and see what happens.
 
um are you sure? I’m pretty sure I read all over the threads in here that 1g turbo 2.0 stock fuel pressure is around 36-37psi.

so my bad just a little clarification on that did some digging a your 1990 GSX fuel pressure operating PSI is 43

I would check both these options (fuel pressure regulator, Crankshaft position sensor) since they are important for proper engine operation

Higher RPMs require more fuel pressure to keep your engine running. Failure of this part could result in rough idle, black smoke or fuel in the exhaust, or engine stalling. You may also notice misfires or smell fuel on your spark plugs, dipstick, or when decelerating. If you notice these symptoms, test your regulator.

these are the standard OEM replacements, so I would utilize them as a reference for operating psi range for your year car
https://www.oreillyauto.com/shop/b/...or-12285/0ce0f00c815f/1995/mitsubishi/eclipse
Operating PSI 46
https://www.oreillyauto.com/shop/b/...or-12285/0ce0f00c815f/1998/mitsubishi/eclipse
Operating PSI 50
https://www.oreillyauto.com/shop/b/...or-12285/0ce0f00c815f/1990/mitsubishi/eclipse
Operating PSI 43

A bad crank position sensor won't supply an accurate signal to the ECU. This can cause problems with acceleration, as the ignition and fuel timing may not be adjusted as needed. You may also notice rough idle, misfires, stalling, or poor gas mileage, or your car may not start at all. Because a crankshaft position sensor is related to engine speed when they fail it may not trigger a CEL light A failing crankshaft sensor is famous for working when the engine is cold and then to stop working when the engine heats up. When you let the engine cool off the sensor will start working again. Testing this sensor's intermittent failure can be difficult due to its ability to start working again
 
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So another update guys,

It seems it could be my MAF that went out. As the car was idling really poorly doing its thing, I went to unplug the MAF and the car immediately corrected itself and, although it threw a CEL and the idle was high, it was running properly again.

Then as I went to plug it back in, it went right back to the very poor low rough idle.

Got a replacement MAF on the way and will see if this finally takes care of this new issue.
 
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