Issues with my KZJ78 (1 Viewer)

[deepcrates]

Hey All,

Wanted to see if anyone had any ideas on starting points here:

All summer my car was driving fine. Then suddenly on a drive I noticed the car not shifting up past 3rd gear. Also noticed it shifting erratically between gears. I was close to home so I went home. Later that afternoon it drove fine.

The problem seemed to disappear and then on the beginning of a longer drive it started acting up again. Drove it home, checked the trans fluid - seemed fine. Then took it for a short drive around the the neighborhood and it completely shut off on me at a stoplight. I tried restarting and it would turn on, then putter and shut off after 20 seconds.

Since then it won’t start. I had some body work done to it that was scheduled before this issue and while it was being done they had some mechanics look at it and say nothing seems wrong with it and it might be the car alarm I installed which has a remote start function that’s causing it not to start.

Now I’ve driven it with that alarm since I got it. I had the alarm installed professionally and haven’t had any issues with it at all.

I’m hesitant to say that the cause of the car acting up has to do with the alarm install.

Would the faulty alarm install really cause the car to suddenly shut off 4 months after the install? Any thoughts on what I should look into? I’m suspecting an ECU issue, but would it just go out suddenly like this?

 

[AirheadNut]

The shifting issue could be your transmission solenoids, they seem to age out and start failing intermittently, causing odd shifting behavior. Replacing them is pretty simple, just drain the transmission fluid, drop the pan, take off the filter screen and all three solenoids are right there; just a bolt and a plug on each one.

The shutting off/not starting problem could be the alarm if the install wasn't done well, it can take some time for poor electrical connections to loosen up enough to cause problems. When I first owned my current LJ78 it would occasionally shut off while I was driving; when I tore it apart for the engine transplant I discovered several dodgy repairs to the engine wiring which were probably the cause. ECU failure could also be the issue, a popped capacitor or burnt out resistor could cause sudden failure.

 

[GTSSportCoupe]

Be sure to check your ECU for leaking capacitors. They're known to fail and cause these sorts of problems.

Open it up, and look for black stuff like this:

 

[deepcrates]

Hey all,

Just got the truck back and popped open the ECU and lo and behold… multiple clusters of capacitors leaking. I count 3 different areas with multiple caps leaking. I bought some nicer Panasonic capacitors and will have my friend try to clean and replace them. Wish me luck. I’ll keep you all updated.

Really appreciate the advice y’all.

 

[GTSSportCoupe]

Good luck. I've repaired one for a friend, and it was tough, as the black stuff ate all the copper traces and vias. I had to reconstruct the electrical traces using wire wrap wire (30awg). Took a lot of effort, and I have electronics training and shop with all the equipment. So just be sure to inspect closely once you've cleaned it up. Also, it's a good idea to seal it with a silicone conformal coating when you're done.

 

[TonyP]

Definitely multimeter all those traces. Leaky caps can damage traces.
Looks like those resistors are starting to lift.

 

[deepcrates]

Good luck. I've repaired one for a friend, and it was tough, as the black stuff ate all the copper traces and vias. I had to reconstruct the electrical traces using wire wrap wire (30awg). Took a lot of effort, and I have electronics training and shop with all the equipment. So just be sure to inspect closely once you've cleaned it up. Also, it's a good idea to seal it with a silicone conformal coating

Thanks for the heads up! Really appreciate it.

Just an update got a replacement ECU delivered today and popped it in and she started up first try. I wanted to just say thank you to both of y’all for the help. I truly appreciate it!

 

[Shyrock]

Thanks for the heads up! Really appreciate it.

Just an update got a replacement ECU delivered today and popped it in and she started up first try. I wanted to just say thank you to both of y’all for the help. I truly appreciate it!

Where did you get the replacement?

 

[deepcrates]

Where did you get the replacement?

I bought one off ebay. Paid a pretty penny, but I really am glad i found a replacement. I’ve seen them on Japanese auction sites as well, but luckily there was one in the US.

 

[GTSSportCoupe]

I bought one off ebay. Paid a pretty penny, but I really am glad i found a replacement. I’ve seen them on Japanese auction sites as well, but luckily there was one in the US.

Did you check caps on the new one?

 

[TonyP]

Did you check caps on the new one?

This. You might preemptively swap the caps out. They'll go bad eventually.

 

[deepcrates]

This. You might preemptively swap the caps out. They'll go bad eventually.

Good call! I will take a look at the new one. Luckily I ordered multiples of all the caps for the old one. Mostly Panasonic and some other brand from digikey.

I was so excited to pop it in and find out if the ECU was truly all the issues. I also wanted to take the old girl for a spin I forgot to check. It’s been probably 4 months since I last drove it.

What have you found to be the typical lifespan for the capacitors?

 

[TonyP]

Good call! I will take a look at the new one. Luckily I ordered multiples of all the caps for the old one. Mostly Panasonic and some other brand from digikey.

I was so excited to pop it in and find out if the ECU was truly all the issues. I also wanted to take the old girl for a spin I forgot to check. It’s been probably 4 months since I last drove it.

What have you found to be the typical lifespan for the capacitors?

Depends on the quality of the capacitor. Around 20-25 years is what I've heard from a couple EEs. There are certainly caps that can last much longer and many cheap Chinese caps that'll spew in your board in a few years.

 

[deepcrates]

Just as an update: had my buddy take a stab at replacing the caps. He was able to swap them out but the traces were completely shot. He did used wire jumpers and for s***s n giggles we plugged it in and it fired up first try. Not ideal, but it worked. Not sure if I trust it for a long drive but it definitely is nice to have a backup in a pinch.

 

[epaul]

If you look up relentless motorsports Tx on Facebook the guy rebuilds 1KZ ECUs all the time if you want to get your old one rebuilt.