SamicUniverse

I drive a 2003 Civic Dx Sedan and Im having a real hard time figuring this issue out. Ive had this car for 4 years now and have been able to diagnose and fix everything up until this point. Here's what happens...
Key turns over and car starts. Battery light is on and the car rises to 2k rpm for about 1 second and then drop down to 1k suddenly and slowly rises to 2k again over about 3 seconds and then drops again. It does this about 10 times or so until the rpm gauge just drops down to 0 (car still running but much richer). Every time it drops, the engine lights blinks and the 5 pin relay under the glove box clicks open and closed.
The car runs really poorly after this. locks itself in 4th gear when I put it in drive (AT) and will only change gears if I manually shift to d3 or d2. Rpm does not want to go over what seems like 3.5k (though my gauge is dead so I have no way of telling) and it seems to be in sort of limp mode. Car wants to stall when giving it gas after idling and is just an all around pain to drive in this condition.
Things I have tried...
- Checking main engine grounds (This whole thing actually started when my alternator belt fell off while driving. I was able to get it back to a friends shop and put the belt back on. My alternator had crapped the bed so i swapped it and now I am having this issue)
- checked alternator as I had swapped it out
- a few other basic things that are escaping my mind
All said and done, I think i should check ecu grounds but im not sure that would be beneficial at this point as alot of the grounds I have checked are functional. My repair manual hasnt been much of help. Any opinions would be much appreciated as Im pretty tired of this by now.

Colin42

What codes?
tried cleaning the iac?

SamicUniverse

have pulled apart the intake manifold recently and it all looked relatively clean. No codes being thrown, which is a huge annoyance

Colin42

Bad ground?

SamicUniverse

that's really what I'm thinking. I don't know how to check grounds on ecu and other parts though. I've checked all my engine grounds and they all have good contacts. Cant find any videos or walkthroughs on a full car ground check. Electrical is the one venue I haven't ever dabbled in besides hooking subs up and checking main grounds (and yes, I've checked the grounds on my sub)

SamicUniverse

Ok so I've been able to narrow it down a bit further. I was checking grounds on my ecu connectors and pin 11 was only showing about 2.5v. This is a sensor ground that links up to g501 which is directly behind the steering wheel. Now my problem is finding where in the line it's faulting. Any suggestions?

Colin42

Checked the repair manual to see what its connected to?
You can pull apart the column and look, just wait a few mins after disconnecting the batter to pull the air bag

SamicUniverse

I was able to find the grounding points and all looks good. There must be a break or bad splice between that and the pin on the ecu. Seems to pop out of the firewall and back in tho, so it's gonna be a real pain tracing this back. I may have to pull either the entire harness or the dashboard to get at it...