Resolved 2GNT ECU failing Intermittently?

[Nova95]

I've been chasing a weird problem with my 96 Eclipse 420a NT for a few months now. Randomly in the middle of driving she'll cut out and will not start back up. Eventually it will start again on its own. Usually after killing my battery first, and having someone jump me for 5-10.

Lately it's gotten worse and she just will not restart. I've replaced the cam/crank sensors, fuel pump, filter, MAP, Ignition switch, coil pack, plugs, wires. With each part I thought I had fixed the problem because it would run perfect for the next two days or so then I'd cut out in the middle of traffic again.

The fuel and ASD relays are good, but the connectors were pretty badly corroded so I replaced both of them. It ran good for a day then same thing. Unplugging the battery for 5-10 minutes allows me to restart it, but then she dies even if I try to gas it as if the fuel just got cut.

Yesterday and today she died in some pretty crappy spots and the only I was able to limp her home was by jumping the ASD relay to the negative on my battery. She tried to cut out but both times I could actually rev her up to 5-6k to stop her from cutting out (finally getting fuel). After about 5 minutes of driving in these RPMs, the car acts perfectly normal again like nothing ever happened. I can unplug the jumper wire and use the car as normal for the rest of the day till it decides to die randomly again, usually the next day.

Oh and the car is not throwing a single code for me to even try to work with. What is going on? Could my ECU be failing just sometimes?

 

[Nova95]

Checked plugs that I bought last week and they are already really black. Did a compression test and I'm getting 1 - 112, 2 - 50, 3 - 92, 4 - 80. I did this test twice, and I did it after letting it idle to operating temp. Is this the culprit of my issues?

 

[steve]

That's got to run rough as hell but I don't see how it directly relates to the described behavior.
The min spec for compression is 100 psi (normal 170-225 psi) and max diff between all cyls is 25%.

Your almost 50% between the worst and any other.

 

[luv2rallye]

I don't and have tried to ignore 2GNT's but I guess I need to do an ASD write up.

Steve is being modest. With his posts like these:
Turbo ECU power-on sequence:
{https://www.dsmtuners.com/threads/1g-basic-ecu-mpi-relay-circuit-function.435961/}
and
{https://www.dsmtuners.com/threads/car-wont-start-but-has-power.257495/#post-151172645}
and
turbo ECU basic operation: {https://www.dsmtuners.com/threads/fuel-injectors-pulse.256217/#post-151150406},
I think it's obvious he's the turbo ECU expert. Great job!

So yes Steve, a writeup on the NT ECU power-up sequence and basic operation would be awesome too!

 

[Nova95]

Steve is being modest. With his posts like these:
Turbo ECU power-on sequence:
{https://www.dsmtuners.com/threads/1g-basic-ecu-mpi-relay-circuit-function.435961/}
and
{https://www.dsmtuners.com/threads/1g-basic-ecu-mpi-relay-circuit-function.435961/}
and
turbo ECU basic operation: {https://www.dsmtuners.com/threads/fuel-injectors-pulse.256217/#post-151150406},
- I think it's obvious he's the turbo ECU expert. Great job!

So yes Steve, a writeup on the NT ECU power-up sequence and basic operation would be awesome too!

Well I'm sure wishing I had a dang turbo right about now that's for sure

 

[luv2rallye]

Checked plugs that I bought last week and they are already really black. Did a compression test and I'm getting 1 - 112, 2 - 50, 3 - 92, 4 - 80. I did this test twice, and I did it after letting it idle to operating temp. Is this the culprit of my issues?

Probably and even if not, it's a major problem keeping the engine from running correctly. When you did the compression test where you holding the throttle butterfly (on throttle body) wide open while cranking (or holding the accelerator pedal to the floor)?

 

[Nova95]

Probably and even if not, it's a major problem keeping the engine from running correctly. When you did the compression test where you holding the throttle butterfly (on throttle body) wide open while cranking (or holding the accelerator pedal to the floor)?

I didn't touch the accelerator pedal for any of the test, Should I have been? I only held down the clutch with the coil pack unplugged. I can go retest right now if needed.

It's interesting with the compression test cause I being an idiot only unplugged 3 of the 4 spark plug wires, just off of the 1 plug still in, the car started. Sounded like crap, but it did start with just the one plug.

 

[luv2rallye]

I didn't touch the accelerator pedal for any of the test, Should I have been? I only held down the clutch with the coil pack unplugged. I can go retest right now if needed.

Yes re-test holding the accelerator pedal to the floor while cranking (so it gets normal air flow) while reading compression gauge on each cylinder one at a time with all plugs removed. Engine warmed up but just cranking with no way to start (eg ASD unplugged).

 

[Nova95]

Okay retest came to 1 -110, 2 - 80, 3 -90, 4 - 82.

 

[luv2rallye]

Yep those are terribly low compressions and are (or definitely will be) a problem.

 

[chrysler kid]

It's interesting with the compression test cause I being an idiot only unplugged 3 of the 4 spark plug wires, just off of the 1 plug still in, the car started. Sounded like crap, but it did start with just the one plug.

youre not suppose to have fuel spraying in the cylinder while you are doing a compression test.

you should have all the plugs out and all of the fuel injectors unplugged. you should be holding the gas pedal down while cranking over the vehicle. you want to crank the car for ten to fifteen seconds or until the compression gauge stops building pressure

the compression numbers indicate you are doing the test wrong or the motor is blown. it takes 100psi in a cylinder for it to mix air fuel and spark correctly to detonate.

the numbers you posted indicate that your engine is garbage and you need a new motor. but I think you are doing a compression test wrong

 

[luv2rallye]

Here's how to do a compression test properly and completely. It's written for the turbo but will work for your NT also if you unplug the ASD relay (which removes power from the coils and injectors).

How to do a Compression Test

 

[Nova95]

Yep those are terribly low compressions and are (or definitely will be) a problem.

Well shit. Can I pop the pistons through the head from the oil pan?

Here's how to do a compression test properly and completely. It's written for the turbo but will work for your NT also if you unplug the ASD relay (which removes power from the coils and injectors).

How to do a Compression Test

My battery wasn't 100% when I did the test, I'll charge it fully today and try again this evening.

 

[steve]

Well shit. Can I pop the pistons through the head from the oil pan?

People have but right now you don't have any idea of why your compression numbers are low.
Could be your procedure (since that helped last time). Could be valves, or rings, or cylinder bores, or timing, or a combination of things.

 

[luv2rallye]

Yes. Do every test you can now (eg. compression, leak-down, fuel pressure, spark, etc). Once you've pulled the head it's too late, plus you've then changed things so testing for things like compression and leak-down won't mean anything - even if you put it back together (not to mention most tests you then can't do with the engine apart).

 

[BLACK'98DSM]

Re-test your compression, properly this time. In the past a weak battery has made the difference of 30 psi per cylinder for me. Just depending how slowly the starter is rotating the assembly. And unplug the injector harness so you aren't spraying fuel in your tester. Liquid does not compress like air.

 

[Nova95]

Still waiting on full charge on the battery to retest. But today I put the ASD relay back in and crossed my fingers on driving it to work. It drove there and home and was even able to stop by the grocery store with absolutely zero issues, didn't stall or hesitate once. It actually felt like it drove better today than usual. I've noticed in the past it almost seems to me that it drives and acts better when it's been raining all day. Maybe my ECU is acting up when its hotter out or something? Idk. I'll post back when compression is done correctly

 

[luv2rallye]

Still waiting on full charge on the battery to retest. But today I put the ASD relay back in and crossed my fingers on driving it to work. It drove there and home and was even able to stop by the grocery store with absolutely zero issues, didn't stall or hesitate once. It actually felt like it drove better today than usual. I've noticed in the past it almost seems to me that it drives and acts better when it's been raining all day. Maybe my ECU is acting up when its hotter out or something? Idk. I'll post back when compression is done correctly

Perhaps but I doubt it. Moist air is usually colder and so is denser which gives better engine air/fuel performance (more of it) and so slightly more hp. So it's likely misleading you into thinking the ECU is cooler. My father who worked on WWII bombers said they would inject water into the B17's engines just on takeoff to get more power to get the heavy load off the ground.

When you stomp on it driving around, do you get normal (or at least good/fair) acceleration or does it miss and bog down?

Remember to unplug the ASD relay when you do the compression test so coil and injectors won't get power.

 

[Nova95]

Perhaps but I doubt it. Moist air is usually colder and so is denser which gives better engine air/fuel performance (more of it) and so slightly more hp. So it's likely misleading you into thinking the ECU is cooler. My father who worked on WWII bombers said they would inject water into the B17's engines just on takeoff to get more power to get the heavy load off the ground.

When you stomp on it driving around, do you get normal (or at least good/fair) acceleration or does it miss and bog down?

Remember to unplug the ASD relay when you do the compression test so coil and injectors won't get power.

When driving around it feels fine. No bogging or missing.

Compression test is:
1 - 120
2 - 90
3 - 95
4 -105

 

[Nova95]

Looks like compression is bare minimum which needs to be addressed, but probably not my cutout mid drive issue. So I just did another drive with the relays still in and did cut out on mid drive, I let it coast a few seconds then dropped it into 2nd from 4th and floored it and it kicked back into life twice. It's looking like I definitely should replace the fuel regulator and maybe injectors I presume at this point. They are a little more pricey than I imagined so I won't be able to buy into that until next week.

 

[steve]

I don't see how you have any data to suggest a fuel regulator or injectors.

What exactly is your battery voltage doing when the car is off and again when it's idling?

 

[Nova95]

I don't see how you have any data to suggest a fuel regulator or injectors.

What exactly is your battery voltage doing when the car is off and again when it's idling?

Considering I've replaced the fuel pump, and fuel filter within the month, and the only way to stop my car from cutting out in the middle of traffic, is by slamming the throttle, leads me to believe that somewhere in my fuel delivery system is the culprit. Which at this point leaves either the fuel pressure regulator or the fuel injectors themselves to potentially be the problem. What data would you suggest me find to rule out the fuel pressure regulator or a possibly bad injector? Give me a sec to go check voltages while off vs idling.

 

[Nova95]

Voltage off is 12. Voltage on is 14.

 

[luv2rallye]

Which at this point leaves either the fuel pressure regulator or the fuel injectors themselves to potentially be the problem.

I wouldn't spend $ on replacing the injectors yet, they are pricey and there's still many other things it can be. Don't be one of those who just keeps throwing $ at it replacing one thing after another guessing, and all that for nothing. Instead do testing, swapping, and experimenting to pin it down.

 

[Nova95]

Alright I'll work on getting a fuel gauge to test all of that soon

 

[steve]

Voltage off is 12. Voltage on is 14.

Good, Alternator seems to be charging so that doesn't seem to be betting the battery run down and stall the car.