420A weak brakes can't figure out why.

[96WhiteEclipse]

I have a 1996 Eclipse GS. I've been having trouble with the brakes for a long time. When i bought the car the brakes were spongy, and they still are spongy even after:

Replaced master cylinder (I did do the bench bleed)
Replaced all brakes
Replaced all soft lines going from caliper to hard lines
Bled the brakes furthest to closest
Replaced the brake fluid

Here where the fun part lies, recently I washed out my engine bay and i was stupid and caused quite a few problems, water got into the TPS and IAC. it started in the beginning with my transmission shifting really hard and not going into overdrive, meanwhile the 30 minute drive before this started happening, my brakes felt great, they had never felt so good, they were firm but not too firm, and they could lock up the front wheels for once in the time I've owned the car.

After realizing i broke some parts i replaced my IAC valve and TPS, after replacing those and getting ready to go for a test drive my car starts idling extremely rough. I disconnect the coil to cylinder 3 while it was running and nothing changed. I then disconnected the injector and nothing changed. Not wanting to shotgun parts i decided to see if any water got into the ECU connectors. they were perfectly dry but i still blew out any dust or possible contaminates on the connector pins. After reconnecting the ECU I started it and it ran fine, no bad idle, all 4 cylinders were firing. After driving it though, the brakes were back to usual.

After all of this, it leads me to think that this is somehow an electrical issue but I don't understand how that would be when I don't have ABS. please help.

 

[BLACK'98DSM]

The brake system has no electrical components besides the brake light switch and the brake lights, so I think you can rule out an electrical issue for this specific problem.

The only way I could see a misfiring engine having any effect on braking is because it will produce less vacuum, therefore weaker operation of the brake booster. So that would almost lead me to believe there is a brake booster issue. But usually a bad brake booster will cause the pedal to be harder to press, not softer. So I hate to say replace the booster without being sure but it's a possibility. Perhaps it has a vacuum leak, and with less vacuum being produced by the engine the leak isn't as aggressive and allowed more vacuum function of the booster than usual. But that's a technical long shot.

In my opinion the factory brake system is weak and never felt very nice. But unless you're slowing from high speeds or trying to accelerate & brake simultaneously then they shouldn't give you much issue and still stop the car safely.