What a nice REPU! great job on the build, the engine bay looks really nice, love those ITB's.

Thanks, still could use a little tidying up, but I'm happy with how it turned out. Trying to drive it as much as possible now since it was off the road for over a year. I'll make a video walk through soon.

Amazing. I love it.

Very nice truck you've got there. The intake and ignition are really nice, but I think my favorite part has to be the re-wire. That is truly impressive and you deserve your props for that. I never thought of wiring as being particularly hard, but it certainly can get tedious and frustrating, so I know there had to be days/nights when you were close to slitting your wrists. Now it's time to enjoy.

I did my research ahead of time and bench tested several of the more complex circuits to ensure I wasn't guessing when it came time to hook up the wipers and lights for the first time. The only frustration I had was realizing I had to add a wire here and there. I haven't pulled the harness to bundle everything with electrical tape yet, and I'm glad I installed it first.

Example 1: ground wires. I grounded the ECU to the firewall at first. This is apparently not wise as the radio was also grounded to the firewall (but in a different spot) and introduced alternator whine into the speakers. Afterward, I ran a new wire through the bulkhead connector so it could be grounded to the engine block. I get overall higher voltage readings in the logs and I think it helps with consistent fuel metering from the injectors.

Example 2: at first I tried no idle control valve but the truck needs a few minutes to warm up. If you want to just get in and go it's necessary no matter what people tell you. I ran two wires at first, for a Ford style valve but couldn't get it to work. There wasn't enough vacuum to close it when needed. So I ran another wire and now use a Bosch style valve. It works well but I still need to tip in the throttle to start the truck. Not sure if it's air or fuel related. An expert could probably tweak my ECU settings and resolve it.

Example 3: I've added a few more circuits like the clutch input and I control the shift buzzer with the ECU instead of it going off at 6,000 RPM or whenever it damn well pleases.

I suppose I could have planned ahead for all of these but this was my first rodeo. I'm about to start an EFI conversion on my Rx7 and it should go pretty smooth now that I know more about each of the inputs and outputs on the ECU.

I now understand why wiring harnesses cost so much. The connectors aren't cheap, and there is a lot of labor involved. It can be just as rewarding as getting your hands greasy and you'll look at people's engine bays a lot differently after you make your own harness.

It sounds like you enjoy a bit more than I do. :D No, but seriously, I hear you. I'm in the middle of wiring up my second aftermarket EMS and you mentioned two keys points that I learned. The first is not to try to "pretty up" the harnesses before you actual get the car running. I learned that the hard way and I'm behaving accordingly with this one. The second is realizing just why custom harness cost so much. Quality parts and the amount of time and labor needed to do it RIGHT is insane.

My first introduction to modding was with car audio so the wiring comes naturally. I had some pretty junk cars in high school that had great audio systems. I had bigger plans for this truck but the cab is so small it doesn't really need or have room for a serious system. I got the headrest speakers and thumpers in the Miata seats working and that's it for audio for now.

This is great. I didn't know you had a whole thread for your truck. I always like when it pops up on your RX-7 thread.

Thanks. There is a bit of an update on this project as well. It's been at the local rotary specialist dyno shop since early October. I brought it in to get the tube cleaned up on the dyno and the transmission did not like the dyno. The linkage broke and it got jammed into 3rd gear. Rather than pay for a rebuild I sourced a 5 speed out of an RX4 which is something I wanted to do eventually anyway. I had it shipped to the shop and there has been much confusion since.

First, the seller sent the wrong transmission, so the shop couldn't find 5th gear. Then the seller sent the right transmission but the shop didn't think the bellhousing was going to work (it was, they just had to give the lower shaft a light tap with a rubber mallet). They ordered a new throwout bearing but it turned out to be the wrong one because it wouldn't work with my throwout fork. The correct bearing was really expensive so they had me send them a fork from my spare 1st gen transmission. I haven't heard back since then. Hopefully they can get the new 5 speed back in so I can take the truck for a few drives before I store it for the winter.

The new (to me) 5 speed
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Side by side while they were having trouble with the bell housing
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The lower shaft bearing was the issue
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Checking the size of the fork from my spare trans
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Cleaned up the fork before giving it to them to install.
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Patiently waiting for the trans to go in.
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Well, I am getting punished for trying to just drop this 5 speed in. The trans mount doesn't line up. They say it's off by over 2" and there isn't any clearance for just a plate. Silly me for thinking this would be an easy upgrade.

Sorry didn't see this tread soon enough, I could have told you, you have to notch the old cross member (not recommended) or make a new cross member. I made a new cross member. everything else worked good.

Yeah, the shop said they didn't recommend trying to modify the original, so they're fabbing up a new one for me.

I bet those ITB's sound sweet

Got the truck back yesterday.

The good news:

At partial to full throttle it pulls like a beast all the way past 8,000RPM. It idles fine and doesn't stall anymore. Cold starts and hot starts are pretty much turn-key. Hot start was a little rough but a quick blip of the throttle and it settled. The new transmission feels amazing, shifts are so much tighter. I had gotten used to the sloppy 4 speed so this was a major improvement.

The bad news:

1) It's fast idling around 1,600-2,000 RPM because the throttle is sticking. After some investigation I believe this to be the TPS sensor preventing the throttle from fully closing. I had issues with it before, I think I'll just replace it.

2) The tachometer is way off, redline is way past the gauge.

3) The speedometer is way off, I'll have to swap speedo gear from the old transmission

4) The header to midpipe exhaust gasket is failing again. This keeps happening, likely because there is no flex pipe and it's only 2 bolts. I guess I'll remove the header and try to flatten the flange incase it's warped.

The really bad news:

The engine is mis-firing like crazy at 5% throttle, ie cruising. It's worse in lower RPMs. It goes away off throttle or when giving more throttle. I've done a few tests since picking it up trying to isolate the issue but haven't figured it out. So far I've tried blocking off all the unnecessary vacuum ports to make sure there isn't a vacuum leak. I tried setting the ignition timing to a fixed advance. I tried backing off their spark-split settings. I tried switching back to open-loop to make sure it wasn't closed loop chasing a setting, or the exhaust leak messing with the O2 sensor readings. I will try some new spark plugs next, and figure out how to test the coils in case one of them is failing. It was not doing this when I dropped it off. It may have been running rough for other reasons, but it always cruised fine around town and on the highway. There is also a chance it's a wiring issue, but if something was loose it would happen at all engine speeds/rpms/loads and this is pretty easy to replicate at 2,000 RPM and 3-5% throttle. I'm really hoping it isn't an internal issue like a bad seal. They said it wasn't, since the motor pulls hard on the dyno and idles fine and has good compression.

sorry to hear about the bad stuff, but....... glad that 5speed is finally in and working great for you!!! enjoy and see you at DGRR my friend

Solved the speedo problem. Still can't figure out the misfire. Replaced the spark plugs but that's not it.

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What am I looking at here. did you find that the stock gear was the problem? What is the new one from?
Mine bounces like crazy but doesn't bother me enough at the moment but finding a fix would be great.
Also I love going back over your threads to figure out what I am going to work on next.

These are the speedo gears from the tail section of the transmission, where the speedo cable connects. When we put in the 5 speed, it came from a truck with a taller final drive (3.90) than my truck (4.11). So I took my original gear and dropped it into the 5 speed and all was good. I still have some speedo bounce but greasing the cable and cleaning and oiling the innards of the gauge helped with that.

I've been driving the truck a bit more lately, still doesn't run great but I solved the misfire issue, it was unbalanced front/rear throttle plates. The throttle still sticks and I think I need to figure out a new cable bracket. The tune is good for cruising but the transients are horrible. If I get it right on initial tip in, it goes lean a moment later in the log, and if I fix that it basically floods the engine under low RPM blips. I have narrowed it down to a possible fuel pressure issue or fuel delivery through the original 5/16" and 1/4" lines. because every setting I try in the ECU doesn't help. My winter project might be to install an in-tank fuel pump and bend some new 3/8" hard lines.

Another issue I had was extended idling would cause the air temp to rise dramatically whether the electric fan was on or not. I installed a heat shield but that didn't help. Then I added a new air box. It took 6 months for the box to come in due to order issues...I had actually given up hope on it coming when it just showed up. Anyway, it looks cool, and I can pull air from lower in the engine bay instead of sucking in air that rises off the header. Of course it's too late to test whether it lowers intake temps.

Took home "Best Mazda" at the annual Japanese Car Day lawn event.

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