CrypticDemise

The car is a 1991 hatchback with factory dual cam KA, 140k miles, factory auto, 5 speed swapped. I've always noticed the car seemed to have a bit of hesitation and never seemed as fast as my previous s13s. Valve stem seals went bad and I finally got around to replacing them as well as a ton of parts on the car because I also pulled the IM to delete PCV/fix vacuum leaks.

After I replaced all this stuff, I wanted to tackle the hesitation, and it seems more present now than ever. At first, I noticed taking off in first gear, the car would really bog down, but was smooth after that. Now, just about anything under 3000 RPMs in any gear with more than 1/4 throttle makes the car misfire/bog/stutter really bad. If I go easy on the throttle, it's fine. After 3k RPM, car smooths out, but feels gutless (may just be that I forgot how slow an NA KA is).

First, I checked the ECU codes, and got 34. Replaced the knock sensor and it was still there. Wasn't getting voltage at the ECU so I checked the harness and found a break above the fuel rail area. Fixed that, ECU now sends 5 volts KOEO as it should, 2.5 volts with engine running/sensor connected. No more code 34.

Then it started showing code 13. This is where I'm stuck. CTS is brand new nissan, PN 22630-51E02. Checked resistance and it was reading normal, around 1300-1600 kOhms with engine cold, 300-ish kOhms at operating temp. Spliced in a new connector because it was cracked and corroded. Connector pins have 5 volts disconnected, KOEO, but when I connect the plug into the sensor, it reads around 2 volts. I assume this is normal? There is continuity from the connector to ECU pin for both power and ground. Swapped the ECU for a manual one I had from a parts car (verified working) and code 13 still comes up.

I replaced the sensor for the dash gauge because it was starting to act erratic, jumping to hot and cold randomly. Now, the gauge just never gets to operating temp. Bleeding the coolant system for 10-15 mins and the gauge just starts to touch the C. Driving it for half an hour, I managed to get it to the second tick mark above C, but it just goes back to C randomly whenever it chooses to.

Upper rad hose is hot, lower rad hose is fairly cool, but I figure this is normal since the KA has a reverse-flow coolant system. Cracking open the bleeder screw, burning hot coolant comes out, so surely the temp sensors are submerged in hot coolant, but both seem to be malfunctioning. I figured my gauge cluster may be the issue, not my temp sender, but it is odd that the ECU says the 2 pin CTS isn't working properly either.

Car has a 248/248 cam swap and idles pretty good when I first start it. Once the rad gets hot, the idle seems to raise up from 900-ish to 1300-1500 RPM, which seems to be a symptom of code 13 from the research I've done. Driving around, the car dies anytime I put the clutch in while the car is still moving.
I really don't suspect MAF (usually causes issues in higher RPM range) or vacuum leaks (would present more idling issues), nor do I suspect fuel (unless its FPR?). TPS is set at 0.49 volts with throttle closed. I was convinced it was a sensor, and the CTS would really explain these issues, but why does my ECU think there is a problem if I have continuity, a new sensor, and hot coolant? Are both ECUs screwed up and reading code 13 somehow or is there something else that can cause code 13? Is it possible I just need more engine bay grounds after my battery relocation?



Parts replaced:
Swapped fuel rail/injectors for a rail and injectors from a known working KA, didn't remove injectors from rail so I highly doubt injector seals are the issue, car tries to die at idle when unplugging any injector
Spark plugs/wires less than a year old, NGKs
Z32 fuel filter less than a year ago
Walbro 255 installed yesterday
CTS for ECU and dash gauge replaced last week, OEM nissan replacements
New coolant, bled properly, car has shrouded clutch fan, dual e-fans, ebay radiator
Lots of vacuum hoses replaced, EGR and literally just about every emissions system has been deleted properly
Battery relocated last week, cleaned engine bay grounds and replaced ground strap at back of head above headers
Knock sensor
Cleaned IACV a week ago