1990 ka24e swap. need some insight

[wildmaninid]

Hello. My name is Bill, known as Wildman. I have a 1977 Datsun pickup that I put a 1990 KA24e engine in. Engine block was actually from a hardbody, but intake and wiring/ecu are from a 240sx with a 5 speed. I also used the truck transmission.

Here is the issue.
This thing runs like a raped ape. I can push her hard in first, and second, and about the time i hit my stride in third gear, the fuel cuts out, and will not come on again until the engine slows to around 3k rpm..then starts running again. I can run the engine up to about 3600rpm on the hiway and then it shuts fuel off, then back on at 3k....

WTF is going on. I have just basic fuel and spark functions working. No egr, no VSS, no 5th gear switch etc. Anyone else ever had this problem on their car? DO I need to put a VSS signal to the ecu? I have grounded the 5th gear switch to no avail.

Please any insight would be amazingly helpful. I am saavy and have no problem with advanced diagnostic etc.

Here are a few oics of my last few weeks with this swap.







last one is a running video, click on the oic for a look see

thanks for any help you may be able to give me!
Bill

[biggie]

Some more familar with SOHC should come by soon.

But have you tried a different ECU for starters? Maybe a AT ECU instead of MT (shouldn't have any speed limiter). If you need one I have a couple extra.

[wildmaninid]

Biggie,

I live in North Idaho. 240's are rare birds in this part of the country. I have had a helluva time sourcing the parts i did. I have been told that an auto ecu #11 or #14 would work. I am just looking for an answer as to why I cannot make this one work. What does the manual ecu look for that the auto one doesn't? Tonight I am going to simulate a vehicle speed signal to feed the ecu using an old abs sensor and the driveline yoke to generate a signal.

Just seems crazy to me that the computer seems to time out so to speak.....

Do/can people remove the top speed limiter or rev limiter? I have read that some remove the 5th gear switch then switch the vss wire off to overcome the ecu, but not sure if that is on the 90 or not. I am just imagining that since the ecu is seeing throttle demand and no speed signal it limits the rpms.

Thanks for the reply, I may need one of these ECU's from you LOL

Bill

[biggie]

The MT ECU limits on speed, 115mph I beleve.

I know some ROM tuning companies can remove the limiter, not sure about DIY on it.

Maybe possible that you have a bad ECU to start with, that's my first and only guess at this point. Others with SOHC may have other ideas.

[compactfean]

I think your ecu is receiving a signal from somewhere for speed signal. I run no 4th and 5th gear sensors, and used to not run speed signal until I installed launch control and never had any fuel cut issues. I would completely unplug all three and get back to us. Your idea of simulating a speed signal will not work because the way the ecu sees the speed signal. The speed sensor creates an ac signal that goes to the gauge cluster. The speedometer then converts that signal to a a signal that can be used for the ecu. (can't remember if its dc voltage or square wave) and the ecu literally has a wire from the cluster to the ecu because the signal coming straight from the sensor cannot be used.

[wildmaninid]

I have determined that about 4 minutes ago by looking at wiring diagrams. I see that everything runs through the cluster first. What I have is a nissan hardbody engine and trans, and a 240 intake/ecu wiring. The hardbody trans has no vss, its running a speedo cable still. So here is what is hooked up on the ecu:blk/pink pin # 106fp lss, black/yellow air regulator, brown aac valveto key power, black w/red ecu pin 36 to power, red/blk ecu piin #4 eccs lss to power, power to pins # 109;38;47, constantpower to ecu pin #46 ecu bup, ground and #34 hooked to the starter wire to cycle fuel pump when cranking. There are no vss or fifth gear switch present, and no place for them to come from obviously since I'm not using a 240 trans.

Is this happening because there is no vss input? Or is there something else. I wouldn't think this is a top speed cut off since there is no speed signal going to the ecu. Maybe some fail safe? If I start the truck and run it hard I get about two minutes of free power until this fuel shutoff problem happens, always at 3500 and then fuel comes on again at 3000:

[compactfean]

I would say its not vss related due to the fact nothing is connected to it and I've never had any issues with all of them unplugged. do you have the tach signal wired to the ecu? I would say its some sort of fail safe so are there any codes? For some reason something screams coil to me.

[wildmaninid]

No, I do not have tach signal. All of the codes lead to all the peripheral things not hooked up for the swap. I usually haunt ratsun.net, and several of these swaps have been done over there. All the guys run either a #11 or #14 automatic ECU to overcome this EXACT problem. Everyone who has used a manual ECU has this trouble, swap in an Auto and no more issues. Please don't think I am being a d!ck by trying to make you chase your tail finding a solution to a problem which I already know the answer too, I just have a hard time wrapping my mind around what the hell could be different between the two ECU's to where one has this issue and one does not. My obvious question is answered, that is has anyone had the vss, 4th and 5th switch unhooked and had this issue, seems that answer is crystal clear....no. I think the VSS system is not the issue here and there is some other sort of issue with something being unhooked that is causing this. I believe I am just going to source an automatic ecu, i was just trying to find an possible fix, as there is a show I wanted to drive the truck to on friday, and really would like to have everything working.
Thanks a million for the help guys,
Bill
EDIT* I am sure the ecu is shutting the fuel because when it happens, my tachometer does not drop to 0, it still indicates RPM, which would exclude the coil from the equation, it must still be firing to indicate rpm.

[compactfean]

Come to think of it, some sr20 guys have had close to the same issues with no solution. Good luck and maybe in your journey of this, if you do find the problem let us know because I'm sure it will help some one here a well.

[wildmaninid]

Well thanks! I am actually going to research it further, but for now I am going to buy an auto ecu so I can drive my truck to its new fullest potential. I have upgraded steering, put on 4 wheel disc and I am ready to step up from the 90hp l-series engine I had and enjoy the KA24! I have over 130 hours in this project, including painting and engine overhaul, and I am ready to drive it. I will keep researching this issue, because really this isn't very advanced computer control and I am sure there is just a simple issue, just need to look deeper!
Thanks a million for the help, ideas etc!
Bill

[biggie]

Was going to suggest to try the AT ECU to see if it solved it, seems to be somehow MT/Speed related.

If you can't find a local AT ECU let me know.