HELP! Car keeps setting rev limiter at 1500rpm? Limp mode? STRANGE PROBLEM!!!
 

I can't figure this one out.

I have an Apexi Power FC. Recently rebuilt motor with 1000 miles on it. Full non-sequential stockers (rich man's).

Here is my problem:

The car will drive around fine for awhile - good A/F, good temps, perfect idle, etc. Once in awhile the car will randomly lose all power as if it's going to die, but it just settles at idle. If I try to give it a little gas the rpm's will go up, but the second the rpm's get above 1500 it's like a spark or fuel cut - almost like theres a rev limiter set at 1500.

Sitting in neutral, if I give it constant 1/4 throttle, the rpm's will rev up to about 2300, then die down to 1000, then rev up to about 2300, then die down to idle, and so on. The minute I take my foot off the gas it instantly idles perfectly.

If I shut off the car, hold down the throttle to the floor, and start the car, the rpm's will instantly rev up to 5000 or 6000 and I can rev the car like normal...then after about 4 or 5 seconds, the car instantly loses power (like a fuel or spark cut) and the rpm's will fall to idle. What the hell is that?

I can't figure out WHY it goes into this mode, or HOW to get it out of this mode! It seems to randomly go into this mode, and it randomly goes back to normal. I've tried everything - disconnecting the battery, turning off the key with the rpm's up, letting it idle for awhile, driving around the neighborhood in circles with the rpm's below 1500. Usually after fucking with it for 10-15 minutes it just randomly goes back to normal and I can drive the car again.

Is this something with the ECU? Some sort of Limp Mode? HELP! :wallbash:

---edit---

I've been searching and it sounds like this is the same problem I am having:
https://www.rx7club.com/power-fc-forum-47/pfc-problems-591643/

ughhh i really need help. i can't get the car to go back to normal mode now...anyone? do you think it could be the tps or is it somethign else? help???

Here would be the things I would check:
The last thing changed before the problem started
Your Apexi FC
TPS
Fuel Filter/Fuel Pump/ Fuel system.
Ignition coil/spark plug wires
Alternator
neutral switch
clutch switch (this one aparently can do alot of weird things if not working)

It sounds like you have some sort of intermitant problem, so that will make it harder to diagnose. Check each piece as well as all wiring/ tubing that runs to it, you may just have a lose connection somewhere and it keeps jiggling around. Might also help to watch the engine as it does this, though i doubt it. Of course in the end it could be a bad map or ecu or god only knows what else.

here's my PFC sensor check readout at idle:

PIM: 1.75
VTA1: 0.01
VTA2: 0.01
VMOP: 1.25
WTRT: 1.10
AIRT: 2.26
FUEL: 3.63
O2S: 0.09
STR: o
A/C: o
PWS: o
NTR: x
CLT: o
STP: o
CAT: o
ELD: o
HWL: x
FPD: x
FPR: o
APR: x
PAC: o
CCN: x
TCN: o
PRC: o

(o = open circle, x = solid circle)

Is it bad that VTA1 & VTA2 are both reading 0.01? perhaps that is the problem... even when i step on the gas, the vta1 & vta2 don't really change. they are also hi-lited when i open the sensor check screen...

hey hey! guess what!

went out to pull the TPS sensor off for inspection. first thing i did was pull the harness off. i looked at the pins and also at the harness and noticed a lot of corrosion. cleaned off the pins and the harness, re-connected it, started the car and the problem is gone! now the VTA1 & VTA2 are giving normal readings and the car is running great again.

well, save this one in the archives...haha