KA24E Troubleshooting: Got me on the ropes

[Project Bandwagon]

A bit of backstory first:

1974 Datsun 620, with a 89 240sx KA24E SOHC swapped into it. Immediately after swapping the ka in, i was running the 5 speed ecu until i could get an automatic ecu.

Drove the truck the 30 miles or so home from the shop I was working at, and really the only issue i had was that in 3rd 4th and 5th gear (this was 6 months ago, so i can't say 100%) it would cut out after about 1/2 throttle.

 

I'm Intending to build the truck to drift, I decided to take the truck out to an event (even though it wasn't quite buttoned up)

I'm not sure if it was my wiring, or if i had a relay stick, but about 3 runs into the event, lost everything, did some parking lot diagnosis, and deduced i had fried the 5 speed ecu. towed it home, where it sat for another 3 months while i worked on a few other projects. ordered an auto ecu, got it put in, redid some wiring/relays to ensure that wasn't the problem. i then swapped in the 240 rear end and buttoned it up for this years drift season.

 

The truck runs and drives, but for some reason it's like there's no additional power after 1/4 throttle. it accelerates fine until you hit about 1/4 throttle (no tach installed at this time) but no matter how far you push the pedal, it's the same power as at 1/4 throttle. I've tested and tested, thrown parts at it when the testing led me nowhere, and presently the thing has me on the ropes. i've contemplated pushing it aside and just working on the AE86 I acquired.

 

I come to you begging for guidance.

Here's what I've done so far.

 

Checked Fuel Pressure: If I remember correctly it was about 5psi hi with and without vacuum. Swapped fuel pressure regulators, and fuel filter, but stayed the same.

I am running a walbro 255 in line fuel pump.

 

Checked ECU for codes. I was getting a TPS code, which I recalibrated the TPS and it didn't come back. I also get a 41 code for Intake Air Temp Sensor. This is a MAF setup, so I understand it's part of the MAF sensor. IT is a 3 wire MAF, is one dedicated to the IAT sensor? I can't find any information on this.

 

Checked the intake for any vacuum leaks, and can find NONE. I also double checked the butterfly valves, I deleted the emissions crap, but have not removed the butterfly valves yet, but they are completely open.

 

My fuel injectors were leaking, i replaced all of the o rings, and found one of the caps on one of the injectors broken. i replaced the cap and reinstalled. of course, then i changed the fuel pressure regulator, and now one of the injector upper seals is leaking slightly.

 

Compression was checked before the motor was put in, and was good, but I will check that again this week, since it has been driven and something could have failed.

 

Spark is good, I'm 90% sure timing is still good. I haven't checked that since I swapped in the motor as well.

 

O2 sensor wire looks like it has gotten hot in a couple spots, and honestly this harness has been cut before. I doubled/triple checked everything I could think of, but there's a possibility it's in the harness. I've sourced another one and should have that in a couple days.

 

That's all I can think of at this point, I look forward to hearing some ideas.

And just so it's not ALL reading, some pictures:

 

Here she is hard parked at the last 2 drift events. They've only been a couple miles away, so I've been able to drive it there, but unable to participate.

 

 

 

240 rear end just sitting under the truck so i could figure out a game plan

 

and how she looks with the box on lol:

i have some z car flares that should make it flush(er) lol

 

[jesusno2]

sounds like a MAF problem to me stuck in limp mode. you using a automatic ecu #11 or #14??

[DISLEXICDIME]

coolant temp sensor or maf is my guess

[Project Bandwagon]

#11

I've tried 3 different MAFs. It could be in my MAF wiring. I couldn't find the pin for the white MAF wire. I was going to check continuity then ran out of time.

 

how does one test the ECT sensor? i guess i haven't messed with that at all.

[DISLEXICDIME]

I have herd people say the ground on the single cam maf go's bad and yiu have to add another ground

[jesusno2]

fsm helps http://www.240edge.com/manuals/s13-ka24e.html

 

I dont think a coolant temp sensor will put the ecu in limp mode? it will make it run rich or lean depending on which way the resistance is failing the maf is easy to check the intake temp sensor does 2 things jack and shit.

[DISLEXICDIME]

it will make it run like poo and it will have no power

[Kisor]

3 wire maf does not have the IAT incorperated into it.

 

The blk/wht is the sensor ground, the white is signal voltage. Signal will be ~1-5V depending on air flow. The Black should be 5V reference.

 

Try to take a video of what its doing and post it. Easier to hear and help than trying to explain things via text. lol

 

[Project Bandwagon]

question, in that FSM, in the engine wiring diagram, there's a symbol im not familiar with.

It's in the yellow box in this image

 

[Project Bandwagon]

other question that's been staring me in the face. it only has exhaust about 4 inches past the end of the exhaust manifold

but it ran fine with it that way in 1st & 2nd before. it'll get done, but i'd like to have it running well first

[Spades]

other question that's been staring me in the face. it only has exhaust about 4 inches past the end of the exhaust manifold

but it ran fine with it that way in 1st & 2nd before. it'll get done, but i'd like to have it running well first

 

that depends on how advanced nissans computers are. in some cars that can put you in limp mode...if there is no second O2 after the cat and no resistor on the second O2 sensor to make it think everything is magically ok, you could have an issue. However, you should have some sort of a stored code for it (I would think). Someone else should know and be able to tell you if something as old as an 89 (OBDI system I would imagine) is picky about the secondary O2, and if something that old even has/uses one.

[Kisor]

No second O2 on it. only after '96 and OBD2 will you find downstream sensors.

 

The item in your yellow box is there to indicate that they are shielded wires. they will have a metallic insulation wrapped around them to reduce "noise" from ignition and alternator interference.

 

Whats the deal with the auto pcm? the car is a 5-speed correct?

 

Do you have the trans harness wired right? They do have a speed limiter system that uses gear switches to tell the pcm when you are in 4th and 5th to limit the calculated speed to 115MPH usually.

 

If these are not wired correctly or maybe the use of an auto pcm has it messed up. The auto's used their own control module and borrowed readings from things like TPS and speed sensors to control the trans. Getting a little over my knowledge on how the systems are implemented...

 

May try starting a thread on www.ka-t.org ?

[Project Bandwagon]

i may try ka-t.org.

from what i understand, the manual ecu has to see those sensors from the back of the transmission. the auto ecu doesn't. so with the 5 speed ecu, it was cutting out in i think 3rd 4th & 5th gear. apparently there are several people running this ecu with ka swaps. i am getting my hands on another 5 speed ecu, to see if there is plenty of power in the low 2 gears. if so, it's either that particular ecu, or the auto ecu in general