no speedo short rev limiter

[Kure91]

I tried to search but searching on this new forum kinda sucks.
My friend has a 89 240 (ka24e) and the speedometer doesnt work. Havent really figured out the problem. But the main problem is that he hits the the rev limiter early in 3rd, 4th, and 5th (like 3-5k) and the car just bogs until he puts it in neutral then another gear. The guy told him that if you fixes the speedometer that the rev limiter problem will be fixed. I was thinking it was the ecu but after changing the ecu's out that didnt work. The car is a wiring headache from the previous owner that started a bunch of mini wiring projects but never finished so its hard to trace things.
Has anybody had this problem or have any idea what it could be.

[locoluna825]

more than likly the speedo. had a friend with the exact same problem. put in a new speedo and it fixed the porblem.

[Kure91]

already tried that. thanks though

[locoluna825]

did you try looking at your speed sensor? check if its been damaged, uplugged, or bad.

[Kure91]

yeap i think i know the problem now. previous owner wired in a apexi rsm and i believe its wired wrong. does anybody know what three sensors are connected to the transmission????

[shiro_neko]

I have an 89 240sx as well. my speedo works intermittently and sometimes gives an incorrect signal but It didnt gave me any acceleration problems. try disconnecting the speed sensor harness its in the passenger side engine bay. near the firewall. the connector has 2 thin wires (yellow with blue tracer and yellow with black tracer) this will cut signal to the ECU. sensors in the transmission are for backup lamp switch, neutral switch and 5th position switch (m/t) the speed sensor is bolted into the transmission.