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Discussion Starter · #1 ·
Hello, I've looked and looked, and to no avail.

I am having a serious issue with my 1993 240sx vert(automatic), ka24de stock engine, recently picked it up, 126,000 miles. Very nice pickup, especially here in 2023.

Nonetheless, the issue I have been having has gotten worse as it was driven.
When I start up the car, let it warm up, then go and test drive it, the first rev-up is clean and it revs all the way out. The next time, the car refuses to shift gears, it bogs 4k rpm, 3k rpm, and sometimes lower depending on the speed. You can't gas it if it's been 20 mins of driving, you can only give it 20% gas. It's like it's in limp mode, but I feel if that was the case, it'd stick to just under 3k rpm and not fluctuate. This problem is sometimes inconsistent also...once I was done test driving and decided the issue wasn't fixed, my buddy fiddled with a few things under the hood(pushed some fuses in, moved a few grounds around), went to drive the vehicle and it was perfect until I slowed down to turn around.

Parts I have already addressed:
Spark Plugs
Spark Plug Wires
Dizzy Cap/Rotor
Injectors
MAF
TPS
Coolant Temp Sensor
Ground connected to head, attached to rear fire-wall
Fuel Filter(prev owner)
Fuel Pump(prev owner)

I will say the coolant seems full and completely bled, with no air bubbles.
Any help would be appreciated!
 

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Have you tried reading the ecu codes and see if it pulls a 55 code which means all clear or if it pulls other code they will be flashes. Lon flash is the first number quick flashes are ur 2nd number so if it blinks 2 long blinks and 3 short blink means the code is a 23. Then look up what the number is for the troublecode. Also you should check ur trans harness being an auto ur neutral safety switch could be faulty and not registering rpm and speed correctly. Which would cause limp mode at 2k to 4k rpm. Anther thing you could try is another ecu and see if the problem persists or goes away. Hope that helps you get started.
 

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Discussion Starter · #5 ·
Have you tried reading the ecu codes and see if it pulls a 55 code which means all clear or if it pulls other code they will be flashes. Lon flash is the first number quick flashes are ur 2nd number so if it blinks 2 long blinks and 3 short blink means the code is a 23. Then look up what the number is for the troublecode. Also you should check ur trans harness being an auto ur neutral safety switch could be faulty and not registering rpm and speed correctly. Which would cause limp mode at 2k to 4k rpm. Anther thing you could try is another ecu and see if the problem persists or goes away. Hope that helps you get started.
I appreciate any help, I got a guy with ECUs, and it id like to add it wasn’t bought with the issue. It pretty much started a day or so after it was received, as unfortunate as that is.
 

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So sometimes when a Crank Position sensor starts to fail it will give issues only when the car is at operating Temps. Now if you are clearing codes and running the car it won't throw a code sending you into limp mode until the car gets to operating temps. I would try changing the CPS. Or Crank Angle Sensor. I can't remember what it's called on the S13
 

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Discussion Starter · #7 ·
So sometimes when a Crank Position sensor starts to fail it will give issues only when the car is at operating Temps. Now if you are clearing codes and running the car it won't throw a code sending you into limp mode until the car gets to operating temps. I would try changing the CPS. Or Crank Angle Sensor. I can't remember what it's called on the S13
I’ll give it a look. But I will say it went on a 3hr trip there and back, no CEL thrown. Just cruised at lower speeds, stopped once because the temp went up slightly but when we stopped it shot back down
 

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Discussion Starter · #13 ·
Yea that's not a bog that is definitely limp mode. Just need to Trace the cause of it. I would try a new CPS. Could also be a bad EGR if it isn't already deleted
I was taking a look at EGR , kind of confused on what that is. I heard it was bad, and I also failed to mention that the car has cut offf and stalled twice on that 3hr drive. But it’s made it home nonetheless
 

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Discussion Starter · #14 ·
Another thing to mention, did MAF test, pulled the plug, runs. Did it with the new one while running, continues to run, but when it gets plugged back in while running, it dies. Could also be a link to my issue. Idk, I’m trying to give every piece of info I can to get more precise ideas.
 

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You have a bad maf my friend replace.the maf with a new one not a rebuilt or reused one. Car should not stay running if maf is unplugged should cut right off. Replace maf then come back and tell us if it has been resolved so we have definitive answer wether it worked or not
 

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Discussion Starter · #17 ·
You have a bad maf my friend replace.the maf with a new one not a rebuilt or reused one. Car should not stay running if maf is unplugged should cut right off. Replace maf then come back and tell us if it has been resolved so we have definitive answer wether it worked or not
I mean I figured it was new when I bought it, but I’d be willing to give another a shot.
 

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Discussion Starter · #18 ·
Headed home for the weekend, I will update the forum if the issue becomes resolved 🤞. It sucks looking for a solution to a problem and then coming across a forum that wasn’t updated for others having the same issue. Trust me I know !
 

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Discussion Starter · #19 ·
You have a bad maf my friend replace.the maf with a new one not a rebuilt or reused one. Car should not stay running if maf is unplugged should cut right off. Replace maf then come back and tell us if it has been resolved so we have definitive answer wether it worked or not
Replaced it with an older one , car ran for a good 30 mins just fine until it started hesitating at 5k rpm then slowly worsens to about 3k. Parked at gas station, wouldnt rev past 4k. Turned my car off and back on, revved it out fine. Was shifting kind of hard while driving, but then again it bogs in neutral also.
 
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