420A Random stalling

[Voc19]

I am new to posting here on the forums, I have been looking for a problem like mine but can’t find something similar. I have a 99 Eclipse 420a automatic, I’ve been working on this car about a year now. The person before me had installed a aftermarket alarm system and while fixing up this car I took all that out, because the wires were all cut leading to nowhere and the people before also had some random aux wiring that went nowhere.

Now I have no idea if those wires did anything to do with this problem but for the past 4 months now the car has some random stalls and/or the CEL will come on and off. When the CEL comes on the car always has some random surge or idle will go wonk. Usually when this “hiccup” happens it keeps happening over and over sometimes 4 times sometimes just once. When it happens and the car is in idle it will either turn off or will drop RPMs to like 200 then rev back up then steady out and sometimes will repeat or it'll just die. When I'm driving and CEL comes on there's either some lock up or RPMs will sometimes go up.

IDK what the problem can be. I've damn near replaced all sensors, I’ve replaced the TPS, IACV, camshaft, crankshaft, oil pressure, and the knock. I've took off the intake cleaned that up, cleaned up the throttle body. I’ve replaced the header with some aftermarket headers and replaced both upstream and downstream O2 sensors. I've also replaced the coil pack, spark plugs and plug wires.

I've also recently redone all the wiring and I found some copper showing what I did for those was I'd cut the wires and slide on some heat shrink and reconnect the wire. I also replaced both coolant sensors and also added a thermostat as there wasn’t one before in hopes that was the problem. If anyone has any suggestions that will be much appreciated.

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[VelocitàPaola]

That sounds like a really frustrating problem. My guess is that the connection to one of the sensors is faulty. When the PCM loses the signal, the engine stalls, and that's why the CEL comes on. You should also scan the PCM for error codes, if you haven't already--that might give you a hint.

 

[Voc19]

That sounds like a really frustrating problem. My guess is that the connection to one of the sensors is faulty. When the PCM loses the signal, the engine stalls, and that's why the CEL comes on. You should also scan the PCM for error codes, if you haven't already--that might give you a hint.

i have this nice obd scanner and i have no codes last time i had pulled a code I had the obd scanner hooked up while i drove and pulled a downstream o2 sensor code, i replaced the sensor to no avail. There is another issue that i constantly have tho and thats with the obd port itself under the dash, the port is very finicky with both my more expensive and cheap one scanners. Not sure if that can cause or be caused by something I tried redoing the ground for the ecu under the dash and the ground bolt was stripped i then put the grounds near a piller by the radio under the dash on some metal, maybe thats a problem? Although i couldn’t find another spot to bolt the grounds.

 

[luv2rallye]

Doubt it's a wiring issue.
Nor saying this is it but have you replaced the fuel pressure regulator {FPR} (in case it's leaking)? Worth the effort at this point and FPR's are cheap and wear out with age anyway.
If you have a fuel pressure tester you could also see if the pressure drops (at the rail) when you have the problem (eg. intermittent leaky FPR, or ???), as well as if it's within spec.

 

[Voc19]

Doubt it's a wiring issue.
Nor saying this is it but have you replaced the fuel pressure regulator {FPR} (in case it's leaking)? Worth the effort at this point and FPR's are cheap and wear out with age anyway.
If you have a fuel pressure tester you could also see if the pressure drops (at the rail) when you have the problem (eg. intermittent leaky FPR, or ???), as well as if it's within spec.

Okay just tried to test the fuel pressure with the key to the on i had a psi of about 39-40ish with the engine running it was like 45-60 it was really jumpy, not sure if it was the fuel pressure gauge

 

[Voc19]

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